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					                       TurboSystem




ANSYS, Inc.                          Release 12.0
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Table of Contents
Introduction to TurboSystem ..................................................................................................................... 1
TurboSystem Workflows ............................................................................................................................. 3
    Geometry Sources .................................................................................................................................. 3
    Mesh Sources ......................................................................................................................................... 3
    Solution Sources ..................................................................................................................................... 3
    Examples of TurboSystem Workflows ...................................................................................................... 4
    Usage Notes for Specific Workflows ......................................................................................................... 5
        Tips on using ANSYS Workbench ....................................................................................................... 5
        Using BladeGen ................................................................................................................................ 6
            Changing the Active Document in BladeGen ............................................................................... 6
        Using BladeEditor ............................................................................................................................. 6
            Loading versus Importing a BladeGen Geometry ......................................................................... 6
            Restarting a BladeEditor Session ................................................................................................. 7
            Modifying Spline Curves ............................................................................................................. 7
            Adding a Hub Fillet to an Imported BladeGen Geometry ............................................................. 7
            Creating a Full 360-Degree Fluid Zone for an Impeller .................................................................. 8
        Using ANSYS TurboGrid .................................................................................................................... 8
        Using ANSYS CFX .............................................................................................................................. 8
            Connecting from a Turbo Mesh Cell ............................................................................................ 9
            Changing the Geometry ............................................................................................................. 9
    Quick Pump Tutorial ............................................................................................................................... 9
ANSYS BladeGen ....................................................................................................................................... 13
ANSYS BladeEditor ................................................................................................................................... 19
    The BladeEditor User Interface .............................................................................................................. 19
        Tree View and Details View .............................................................................................................. 19
        Contour Sketch Management ......................................................................................................... 20
        BladeEditor Toolbars ....................................................................................................................... 21
            Feature Creation Toolbar ........................................................................................................... 21
            Active Selection Toolbar ............................................................................................................ 23
            Display Control Toolbar ............................................................................................................. 24
        Angle and Thickness Views ............................................................................................................. 24
            Angle View ............................................................................................................................... 24
            Thickness View ......................................................................................................................... 25
        User Preferences and Properties ...................................................................................................... 25
    Blade Editing Features .......................................................................................................................... 26
        Flow Path Contour Creation ............................................................................................................ 27
        FlowPath Feature ............................................................................................................................ 28
            Flow Cut ................................................................................................................................... 29
        Camberline/Thickness Definition Feature ........................................................................................ 30
            Importing and Exporting Angle Definition Data ........................................................................ 32
            Importing and Exporting Thickness Definition Data ................................................................... 33
            Converting Curves to Bezier or Spline ........................................................................................ 33
            Converting Angle Definition Data ............................................................................................. 34
            Forcing Interpolation of the Definition Data .............................................................................. 34
        Blade Feature ................................................................................................................................. 34
        Splitter Feature ............................................................................................................................... 36
            Cloned Splitter ......................................................................................................................... 36
            Independent Splitter ................................................................................................................ 36
        Stage Fluid Zone Feature ................................................................................................................ 38
        Throat Area Feature ........................................................................................................................ 39

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TurboSystem

    Importing Blades from ANSYS BladeGen ............................................................................................... 41
    Loading and Modifying Blades from ANSYS BladeGen ........................................................................... 45
    Using and Exporting Blades .................................................................................................................. 45
        Export to Vista TF (.geo) .................................................................................................................. 46
        Export as Meanline Data (.rtzt file) ................................................................................................... 47
        Export to ANSYS TurboGrid ............................................................................................................. 48
    Configuring the BladeModeler License .................................................................................................. 50
ANSYS TurboGrid ...................................................................................................................................... 53
ANSYS CFX-Pre ......................................................................................................................................... 57
ANSYS CFD-Post ........................................................................................................................................ 59
Vista TF ..................................................................................................................................................... 61
    Vista TF User's Guide ............................................................................................................................. 61
        Vista TF Setup Cell Properties .......................................................................................................... 62
        Customizing the Vista TF Template Files ........................................................................................... 66
        Vista TF Context Menu Commands .................................................................................................. 67
    Vista TF Reference Guide ....................................................................................................................... 68
        Running Vista TF from the Command Line ....................................................................................... 68
        Input and Output Data Files for Vista TF ........................................................................................... 69
             The Auxiliary File with the Default Name: vista_tf.fil ................................................................... 69
             Overview of Input Files ............................................................................................................. 70
             Overview of Output Files .......................................................................................................... 72
             Specification of the Control Data File (*.con) .............................................................................. 74
             Specification of the Geometry Data File (*.geo) .......................................................................... 83
             Specification of Aerodynamic Data File (*.aer) ............................................................................ 91
             Specification of Correlations Data File (*.cor) ............................................................................ 101
             Specification of the Output Data File (*.out) ............................................................................. 111
             Specification of the Text Data Files (*.txt) ................................................................................. 114
             Specification of the CFD-Post Output Files (*.csv) ..................................................................... 116
             Specification of Convergence History Data File (*.hst) .............................................................. 117
        Software Limitations ..................................................................................................................... 118
        Streamline Curvature Throughflow Theory .................................................................................... 118
             The Equations ......................................................................................................................... 119
             The Mean Stream Surface ....................................................................................................... 119
             The Grid ................................................................................................................................. 120
             Ductflow and Throughflow ..................................................................................................... 121
             Iterative Solution Procedure .................................................................................................... 121
             Initial Estimate ........................................................................................................................ 122
             Radial Equilibrium Equation .................................................................................................... 122
             Combination of Velocity Gradient and Continuity Equations .................................................... 122
             Relaxation Factors ................................................................................................................... 123
             Streamline curvature .............................................................................................................. 123
             Equations for Enthalpy and Angular Momentum ..................................................................... 123
             Boundary Conditions .............................................................................................................. 123
             Empirical Data ........................................................................................................................ 124
             Blade-to-blade Solution .......................................................................................................... 124
             Spanwise Mixing .................................................................................................................... 124
             Streamline Curvature Throughflow Theory: Bibliography ......................................................... 125
        Appendices .................................................................................................................................. 126
             Appendix A: A Note on Sign Convention for Angles and Velocities ............................................ 127
                   Definition of Blade Lean Angles ......................................................................................... 128
                   Definition of Meridional Streamline Inclination Angle or Pitch Angle .................................. 129
                   Definition of Blade Angle .................................................................................................. 129


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                                                                                                                                              TurboSystem

               Appendix B: Example of a Control Data File (*.con) ................................................................... 130
               Appendix C: Example of a Geometry Data File (*.geo) for a Radial Impeller ............................... 130
               Appendix D: Example of an Aerodynamic Data File (*.aer) ........................................................ 132
               Appendix E: Examples of Correlations Data Files (*.cor) ............................................................ 133
               Appendix F: Troubleshooting .................................................................................................. 138
                     Input-output Errors ........................................................................................................... 139
                     Convergence .................................................................................................................... 140
                     Reverse Flow .................................................................................................................... 142
                     Choking ........................................................................................................................... 142
                     Computational Grid .......................................................................................................... 144
                     Other Numerical Issues ..................................................................................................... 145
               Appendix G: The RTZTtoGEO Program ..................................................................................... 147
Index ........................................................................................................................................................ 151




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Introduction to TurboSystem
TurboSystem is a set of software applications and software features for designing turbomachinery in the
ANSYS Workbench environment. It consists of the following components:

 •   ANSYS BladeGen: a geometry creation tool that is specialized for turbomachinery blades. For details,
     see "ANSYS BladeGen" (p. 13).
 •   ANSYS DesignModeler: a general purpose geometry preparation tool that is integrated in ANSYS
     Workbench. This CAD-like program is primarily used to prepare CAD geometry models for analysis by
     other ANSYS Workbench based tools. For details, see DesignModeler Help.
 •   ANSYS BladeEditor: a plugin for DesignModeler for creating blade geometry. ANSYS BladeEditor provides
     the geometry link between BladeGen and DesignModeler, and therefore links BladeGen with other
     ANSYS Workbench based applications. For details, see "ANSYS BladeEditor" (p. 19).
 •   ANSYS TurboGrid: a meshing tool that is specialized for CFD analyses of turbomachinery blade rows.
     For details, see "ANSYS TurboGrid" (p. 53).
 •   ANSYS CFX-Pre: a general-purpose CFD preprocessor that has a turbomachinery setup wizard for facilit-
     ating the setup of turbomachinery CFD simulations. For details, see "ANSYS CFX-Pre" (p. 57).
 •   ANSYS CFD-Post: a general-purpose CFD postprocessor that has features for facilitating the post-pro-
     cessing of turbomachinery CFD simulations. For details, see "ANSYS CFD-Post" (p. 59).
 •   Vista TF: a streamline curvature throughflow program for the analysis of turbomachinery. This program
     enables you to rapidly evaluate radial blade rows (pumps, compressors and turbines) at the early stages
     of the design. For details, see "Vista TF" (p. 61).

For information about using TurboSystem in various workflows, see "TurboSystem Workflows" (p. 3).




                     Release 12.0 - © 2009 SAS IP, Inc. All rights reserved. - Contains proprietary and confidential information
                                                 of ANSYS, Inc. and its subsidiaries and affiliates.                               1
    Release 12.0 - © 2009 SAS IP, Inc. All rights reserved. - Contains proprietary and confidential information
2                               of ANSYS, Inc. and its subsidiaries and affiliates.
TurboSystem Workflows
TurboSystem is a set of software applications and software features that help you to perform turbomachinery
analyses in ANSYS Workbench. The software applications and features are listed in "Introduction to
TurboSystem" (p. 1). This chapter describes the primary ways of using TurboSystem.

The following topics are discussed:
 Geometry Sources
 Mesh Sources
 Solution Sources
 Examples of TurboSystem Workflows
 Usage Notes for Specific Workflows
 Quick Pump Tutorial

Geometry Sources
The turbomachinery geometry is typically provided by one of the following cells:

 •   Blade Design cell of a BladeGen system
 •   Geometry cell of a Geometry or Mesh system

     This can be based on an upstream Blade Design cell.

     If you want to pass the geometry to the Turbo Mesh cell of a TurboGrid system, you must use
     BladeEditor to export to ANSYS TurboGrid.

Mesh Sources
The mesh is typically provided by one of the following cells:

 •   Turbo Mesh cell of a TurboGrid system
 •   Mesh cell of a Mesh system

Solution Sources
You can use one of the following systems to compute and report performance data:

 •   CFX component system

     Use a CFX component system to perform a CFD analysis.
 •   Vista TF component system

     Use a Vista TF component system to perform a throughflow analysis.
 •   Static Structural (ANSYS) analysis system

     Use a Static Structural (ANSYS) analysis system to compute stresses and strains due to fluid forces and
     centrifugal forces.

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TurboSystem Workflows


Examples of TurboSystem Workflows
This section shows examples of TurboSystem workflows, represented as connected systems in the Project
Schematic view. Many other configurations are possible.

CFD analysis of a centrifugal pump:




CFD analysis of a turbine stage:




Throughflow analysis and CFD analysis of a turbine stage:




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                                                                                                                Tips on using ANSYS Workbench




Usage Notes for Specific Workflows
This section describes TurboSystem-related workflow issues and recommended practices:
 Tips on using ANSYS Workbench
 Using BladeGen
 Using BladeEditor
 Using ANSYS TurboGrid
 Using ANSYS CFX

Tips on using ANSYS Workbench
The following is a list of tips that you may find useful when working in ANSYS Workbench:

 •   Try right-clicking on different parts of the interface to see shortcut menus.
 •   You may find Compact Mode to be useful. Select View > Compact Mode from the ANSYS Workbench

     menu or click                   to turn the Project Schematic view into a small, non-intrusive “title bar”
     that is always visible. To return to Full Mode, hover the mouse over the title bar, then, after the window
     has expanded, click Restore Full Mode                    in the upper-right corner of the application window.
 •   Use the Files view to determine which files were created for each cell/system. It is easiest to find files
     associated with a specific cell by sorting the view by Cell ID. This will sort the list by system and then
     by cell.
 •   When selecting a system in the toolbox, ANSYS Workbench will highlight the cells in any systems already
     in the Project Schematic view to which a valid connection can be made.

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TurboSystem Workflows

 •    Give unique meaningful names to all of your systems, especially if there are multiple systems of the
      same type.

Using BladeGen
The following topic(s) are discussed:
 Changing the Active Document in BladeGen

Changing the Active Document in BladeGen
If you want to replace the active document in BladeGen, then:

 1.    Reset the corresponding Blade Design cell.
 2.    Edit the Blade Design cell or right-click it and select Import Existing Case.

Note that opening a subsequent .bgd file in the same instance of BladeGen will not replace the model as-
sociated with the Blade Design cell.

Using BladeEditor
The following topic(s) are discussed:
 Loading versus Importing a BladeGen Geometry
 Restarting a BladeEditor Session
 Modifying Spline Curves
 Adding a Hub Fillet to an Imported BladeGen Geometry
 Creating a Full 360-Degree Fluid Zone for an Impeller

Loading versus Importing a BladeGen Geometry
There are two basic ways of transferring a BladeGen geometry into BladeEditor

 •    Importing

      If you import the geometry, the connection to the BladeGen geometry is maintained, and blade geometry
      changes must be made by editing the upstream Blade Design cell.
 •    Loading

      If you load the geometry, native BladeEditor features are created to represent the complete geometry,
      the connection to the BladeGen geometry is lost, and all geometry changes must be made by editing
      the Geometry cell.

Linking from a Blade Design cell to a Geometry cell causes the BladeGen geometry to be imported into
BladeEditor. The desired import options should be set in the Blade Design cell properties. (See
Table 1: BladeGen Blade Design Cell Properties (p. 14) for more information.) After you make the link, the
Geometry cell should be updated to process the imported geometry.




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                                                                                                                                      Using BladeEditor


      Note

      If you edit the Geometry cell before updating it, then the Import BGD feature details that are
      shown in BladeEditor may not accurately reflect the Blade Design cell properties. To refresh the

      Import BGD feature properties, click           in BladeEditor. It is not recommended that you
      edit the Import BGD properties inside BladeEditor because they will be overwritten by the prop-
      erties from the Blade Design cell the next time you update the Geometry cell.

For details on importing BladeGen geometries, see Importing Blades from ANSYS BladeGen (p. 41).

For details on loading BladeGen geometries, see Loading and Modifying Blades from ANSYS BladeGen (p. 45).

Restarting a BladeEditor Session
If you want to clear a BladeEditor session while maintaining the link to the upstream cell, do not use the
Start Over command from the File menu in BladeEditor. Doing so would erase the incoming data from any
upstream connections — notably when there is an upstream link to a BladeGen system. Instead, return to
the Project Schematic view, right-click the Geometry cell and select Reset from the shortcut menu. When
you subsequently edit the Geometry cell, the upstream data is imported correctly.

Modifying Spline Curves
When a spline is initially created, it is uniquely defined by its fit points. If you move any of the points, the
spline may or may not be uniquely-defined, depending on the way in which you move the points:

 •    If you move a fit point by using the following procedure, the resulting spline will be uniquely defined:

      1.   On the Sketching tab, click Spline Edit.
      2.   Click the spline in the viewer to select it.
      3.   Right-click the spline and select Drag Fit Point.
      4.   Drag one or more fit points to adjust the shape of the spline.

 •    If you move a fit point using the Drag tool on the Sketching tab, or if you change a parameter that
      controls a fit point location, the resulting spline will not be uniquely defined. Such a spline is usable,
      but if you want the spline to be uniquely defined by the position of the fit points, then:

      1.   On the Sketching tab, click Spline Edit.
      2.   Click the spline in the viewer to select it.
      3.   Right-click the spline and select Re-fit Spline.


Adding a Hub Fillet to an Imported BladeGen Geometry
Assuming that you have already created the hub when you initially imported the BladeGen model, you can
add a hub fillet using the following procedure:

 1.    Edit the Geometry cell.
 2.    In BladeEditor/DesignModeler, in the feature tree, right-click the first feature that is listed below both
       the hub and blade features, then select Insert > Fixed Radius from the shortcut menu.

       This inserts a new Blend feature immediately above the feature that you right-click in the tree.

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TurboSystem Workflows

 3.    Select an edge along the intersection of a blade and the hub, for each edge that is to have a fillet of
       a specified size.

       You may need to use viewer toolbar icons to manipulate the view beforehand. If you cannot select

       an edge, confirm that the selection filter is set for selecting edges (the                                            toolbar icon).
 4.    Select Extend to Limits from the toolbar.




       This causes the selected edge to reach as far as possible around the blade.
 5.    Click Apply beside the Geometry property in the details view.
 6.    Set an appropriate value for the Radius property in the details view.
 7.
       Click          .

Creating a Full 360-Degree Fluid Zone for an Impeller
Assuming that you have not created the fluid zone when you initially imported the BladeGen model, you
can create a fluid zone for a full, 360° impeller model using the following procedure:

 1.    View the Blade Design cell properties.

       To do this, right-click the Blade Design cell and select Properties from the shortcut menu.
 2.    In the Properties view, ensure that Create All Blades is selected.
 3.    Update the Geometry cell if required.
 4.    Edit the Geometry cell.
 5.    Create a Revolve feature using the master profile, and revolve it around the axis for the full 360° to
       generate the annulus volume.
 6.    Use an Enclosure feature to subtract the solid impeller from the annulus to generate the desired full
       360° fluid zone.

Using ANSYS TurboGrid
The following is a list of tips that you may find useful when working with ANSYS TurboGrid:

 •    Session file playback in ANSYS TurboGrid in ANSYS Workbench is not supported. It is released as a beta
      feature. For more information about this feature, see the Beta Features section of the ANSYS TurboGrid
      release notes in the online help.
 •    ANSYS Workbench units and appearance options are not passed to ANSYS TurboGrid.

Using ANSYS CFX
The following topic(s) are discussed:
 Connecting from a Turbo Mesh Cell


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                                                                                                                                     Quick Pump Tutorial

 Changing the Geometry

     Note

     For more tips on using ANSYS CFX in ANSYS Workbench, please refer to the ANSYS CFX in ANSYS
     Workbench chapter of the ANSYS CFX online help, which is accessible from the Help menu in
     CFX-Pre.

Connecting from a Turbo Mesh Cell
It is recommended that you connect the Turbo Mesh cell of a TurboGrid system to the Setup cell of a CFX
component system rather than to the Setup cell of a Fluid Flow (CFX) system.

Changing the Geometry
After setting up a turbomachinery simulation in a CFX component system, if you change topology or number
of blades in the mesh, then refreshing or updating the CFX Setup cell (directly or indirectly) will fail to
propagate the new information correctly. This will lead to incorrect results. To compensate, you can manually
correct the number of blades in CFX-Pre by re-entering Turbo Mode (available from the Tools menu). In
addition, the boundaries may need to be manually corrected in CFX-Pre.

If you generate a turbo report in CFD-Post (the latter accessed by editing the Results cell), then subsequently
make changes that affect the upstream solution, and then update the Results cell, the resulting turbo report
will use the updated values for any variables (such as pressure and velocity) and expressions that it uses,
but the report will continue to use the old turbomachinery data (such as the number of blades and the
machine axis). After updating the solution, you will have to take one of the following actions to update the
turbo report:

 •   If you have no work that needs to be preserved with respect to the Results cell, then:

     1.   Reset the Results cell.
     2.   Edit the Results cell.
     3.   Load a turbo report.

 •   If you have done work in CFD-Post but have no work that needs to be preserved with respect to the
     turbo report, then:

     1.   Update the Results cell.
     2.   Reload the turbo report.

     This is slower than the previously-mentioned method because the update process includes an unwanted
     reprocessing of the old turbo report (with new results, but old turbomachinery data). However, because
     this method does not involve resetting the Results cell, any work you have done in CFD-Post is preserved
     (except for any modifications you have made to the original report).

Quick Pump Tutorial
In this tutorial, you will quickly run through the steps required to simulate a water pump while using
TurboSystem.




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TurboSystem Workflows

Designing the Blade and Creating the Mesh
1.   Open ANSYS Workbench and click File > Save As.
2.   Save the project as QuickPump in a suitable directory.
3.   In the Toolbox view, under Component Systems, double-click BladeGen.

     A new BladeGen system appears in the Project Schematic view.
4.   Double-click the Blade Design cell in the BladeGen system.

     BladeGen appears.
5.   Within BladeGen, create a new blade using Vista CPD by selecting File > New > Vista Centrifugal
     Pump Design.
6.   On the Geometry tab, change the number of blades from 6 to 7, then click Calculate.

     The pump design is updated and the results are displayed.
7.   Click Impeller Model.
8.   Exit BladeGen and return to the Project Schematic view.
9.   Right-click the Blade Design cell and select Create New Blade CFD Mesh.

     After some time, a mesh will be created.

          Note

          If you receive an error message about licensing, click Tools > License Preferences and, in
          the dialog box on the Geometry tab, select ANSYS BladeModeler, click Move up, then
          click OK. You should then delete the Mesh system from the Project Schematic view before
          continuing.


10. Right click the Mesh cell of the Mesh system and select Transfer Data To New > CFX.

     A CFX system is added. The additional information requirements posed by the CFX system causes the

     Mesh cell to switch to an 'Update Required' state, as indicated by the                                           symbol.
11. Right-click the Mesh cell and select Update.
12. Double-click the Setup cell in the CFX system.




     CFX-Pre appears.




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                                                                                                  Setting up the Turbomachinery Simulation

Setting up the Turbomachinery Simulation
You will use CFX-Pre in Turbo mode to set up physics and boundary conditions. In this case, you will specify
the same rotational rate and mass flow as specified in Vista CPD.

 1.   Click Tools > Turbo Mode.
 2.   On the Basic Settings panel, set Machine Type to Pump, Rotation Axis to Z, and leave the other
      settings at their defaults.
 3.   Click Next.
 4.   On the Component Definition panel, double-click R1 and set the following values:

      Setting                                     Value
      Component Type > Type                       Rotating
      Component Type > Value                      1450 [rev min^-1]
      Wall Configuration                          (Selected)
      Wall Configuration > Tip                    Yesa
      Clearance at Shroud
      a
        Although, in this case, the geometry and mesh do not model the tip clearance, specifying a tip clearance at the shroud causes
      the entire shroud to be treated as being stationary (via a counter-rotating wall in the rotating frame); otherwise, the entire
      shroud would be treated as being a rotating wall (stationary in the rotating frame).

      Leave the other settings at their defaults.
 5.   Click Next.
 6.   On the Physics Definition panel, set the following values:

      Setting                                     Value
      Fluid                                       Water
      Model Data > Reference                      1 [atm]
      Pressure
      Inflow/Outflow Boundary                     (Selected)
      Templates > P-Total Inlet
      Mass Flow Outlet
      Inflow/Outflow Boundary                     0 [atm]
      Templates > P-Total
      Inflow/Outflow Boundary                     Per Machine
      Templates > Mass Flow
      Inflow/Outflow Boundary                     77.8 [kg s^-1]
      Templates > Mass Flow Rate
      Inflow/Outflow Boundary                     Normal to Boundary
      Templates > Flow Direction
      Solver Parameters > Advec-                  High Resolution
      tion Scheme
      Solver Parameters > Conver- Physical Timescale
      gence Control




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TurboSystem Workflows

      Setting                                     Value
      Solver Parameters > Physical 1e-2 [s]a
      Timescale
      a
       The time scale is approximately 1/(rotation speed [rad/s]). This gives a much more aggressive timescale than the default, for
      faster convergence.

      Leave the other settings at their defaults.
 7.   Click Next.
 8.   On the Interface Definition panel, verify that the periodic interface is set correctly. To do this, click
      R1 to R1 Periodic 1 in the tree view and then examine the associated settings (shown in the
      lower portion of the panel) and highlighted regions in the viewer.

      If no regions appear highlighted in the viewer, ensure that highlighting is turned on in the viewer
      toolbar.
 9.   Click Next.
 10. On the Boundary Definition panel, verify that each boundary is set correctly. To do this, click a
     boundary listed in the tree view and then examine the associated settings and highlighted regions.
 11. Click Next.
 12. On the Final Operations panel, leave the operation set to Enter General Mode and click Finish.
 13. Return to the Project Schematic view.
 14. Right-click the Solution cell and select Update.

      After some time, a CFD solution will be generated. If the progress indicator is not visible, you can display

      it by clicking                              or, to see detailed output, right-click the Solution cell and select Display
      Monitors.
 15. Double-click the Results cell.

      CFD-Post appears.

Viewing the Turbo Report
To see a report for the pump performance:

 1.   Click File > Report > Load 'Pump Impeller Report' Template.
 2.   Click the Report Viewer tab.

Note that if you have visited the Report Viewer tab before loading the template, or have otherwise made
any changes to the report definition after first viewing the report, you need to click                                                 in the Report
Viewer to update the report as displayed.




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12                                                   of ANSYS, Inc. and its subsidiaries and affiliates.
ANSYS BladeGen
ANSYS BladeGen is a geometry creation tool that is specialized for turbomachinery blades. BladeGen has its
own documentation that can be accessed through the user interface, or by browsing the installation directory.

                                                            ,
The main documentation, “ANSYS BladeGen User's Guide” is available from the Help menu in BladeGen.
There, you will find general help, tutorials, and help on a series of Vista programs which run inside BladeGen:

 •   Vista CCD (for centrifugal compressors)
 •   Vista CPD (for centrifugal pumps)
 •   Vista RTD (for radial inflow turbines)
 •   Vista AFD (for axial fans)

     Note

     Another Vista program, Vista TF, is for throughflow analyses in turbomachinery. It has a reference
     guide named "Vista TF Reference Guide" that is in this set of documentation. You can access it
     by clicking the following link: Vista TF Reference Guide (p. 68).

To launch BladeGen from ANSYS Workbench, add the BladeGen component system to your project schem-
atic, then edit the Blade Design cell of that system.

The Blade Design cell has properties that need to be configured in order to transfer the blade geometry
from BladeGen to BladeEditor. This transfer is represented by a link that connects a Blade Design cell to a
Geometry cell.

A sample of the cell properties is shown in Figure : Properties of the BladeGen Blade Design Cell (p. 13).

Figure: Properties of the BladeGen Blade Design Cell




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ANSYS BladeGen

Table 1: BladeGen Blade Design Cell Properties (p. 14) describes each of the cell properties. These are related
to the properties of the ImportBGD feature in BladeEditor (described at Table 3: Properties for the Import BGD
File Feature (p. 42)).

Table 1 BladeGen Blade Design Cell Properties
Group                Name                               Description
Import Options       Create Hub*                        If this property is selected, then
                                                        BladeEditor will create a HubProfile
                                                        sketch for the non-flow path hub geo-
                                                        metry, and will create a revolved body
                                                        feature called HubBody.
                     Create All Blades                  If this property is selected, then
                                                        BladeEditor will create all the blades
                                                        using the number of blades specified in
                                                        the BladeGen model.

                                                        If this property is not selected, then only
                                                        the first blade will be created.
                     Merge Blade Topo- If this property is not selected, then
                     logy              BladeEditor will create the blade with
                                       four faces corresponding to the leading
                                       edge, pressure side, trailing edge and
                                       suction side. This can make it easier to
                                       create a structural mesh for the blades
                                       in the Mechanical application.

                                                        If this property is selected, then the
                                                        blade faces will be merged where they
                                                        are tangent to one another.
                     Blade Loft Direc-                  If this property is set to Streamwise,
                     tion                               then BladeEditor will loft the blade sur-
                                                        faces in the streamwise direction
                                                        through curves that run from hub to
                                                        shroud. This is the default because the
                                                        surface is more well defined, especially
                                                        for flank-milled blades.

                                                        If this property is set to Spanwise,
                                                        then BladeEditor will loft the blade sur-
                                                        faces in the spanwise direction through
                                                        the blade profile curves.
                     Shroud Clearance                   This property specifies whether a shroud
                                                        clearance is created. If None is selected,
                                                        then no shroud clearance is created. To
                                                        create a shroud clearance, choose either
                                                        Relative Layer or Absolute
                                                        Layer. The blade(s) will be trimmed off
                                                        at the selected BladeGen output layer,
                                                        and the layer contour will be created in
                                                        the LayerProfile sketch.


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                                                                                                                      ANSYS BladeGen

Group   Name                               Description
                                           If Relative Layer is selected, then
                                           the selected Layer Number is relative
                                           to the shroud layer, e.g., 1 implies the
                                           first layer closest to the shroud layer, 2
                                           implies the second closest layer to the
                                           shroud, etc.

                                           If Absolute Layer is selected, then
                                           the selected layer index counts up from
                                           the hub layer, which is zero.
        Create Fluid Zone*                 If this property is selected, then
                                           BladeEditor will create a StageFluid-
                                           Zone body for the flow passage, and
                                           an Enclosure feature to subtract the
                                           blade body. The resulting Enclosure can
                                           be used for a CFD analysis of the blade
                                           passage.
        Create Named Se-                   If this property is selected, then
        lections*                          BladeEditor will create NamedSelec-
                                           tions (regions) for the typical faces of
                                           the blade passage, i.e., Blade, Hub,
                                           Shroud, Inflow, Outflow, Period-
                                           icA and PeriodicB. These
                                           NamedSelections can be used as
                                           selection groups in other ANSYS Work-
                                           bench applications, e.g., as regions in
                                           CFX-Mesh.

                                           Note that this property is available only
                                           if Create Fluid Zone is selected.
        Blade Extension                    This property defines the surface exten-
        (%)                                sion length (as a percentage of the av-
                                           erage hub to shroud distance) for the
                                           blade surfaces. These surfaces are exten-
                                           ded and then trimmed to the Master-
                                           Profile sketch to ensure that the
                                           blade solid correctly matches the hub
                                           and shroud contours.
        Periodic Surface                   This property defines the surface exten-
        Extension (%)                      sion length (as a percentage of the av-
                                           erage hub to shroud distance) for the
                                           periodic surfaces. These surfaces are
                                           extended to ensure that the StageFlu-
                                           idZone is properly cut.
        Periodic Surface                   This property specifies the style of the
        Style                              periodic interface surfaces.

                                           If Three Pieces is selected, then the
                                           periodic surface is created in three con-


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ANSYS BladeGen

Group                  Name                               Description
                                                          nected pieces: one upstream of the
                                                          blade, one within the passage, and one
                                                          downstream of the blade. This style can
                                                          better accommodate highly curved or
                                                          twisted blades, and is similar to the
                                                          ANSYS TurboGrid style of periodic sur-
                                                          face.

                                                          If One Piece is selected, then the
                                                          periodic surface is created as a single
                                                          surface.

                                                          Note that this property is available only
                                                          if Create Fluid Zone is set to Yes.

* These properties will only apply when you initially import the model. Any subsequent changes to these
properties will not be propagated to downstream cells upon updating the latter.

Once the ImportBGD feature has been created (for example, by updating the Geometry cell), changing the
following Blade Design cell properties will have no effect:

 •     Create Hub
 •     Create Fluid Zone
 •     Create Named Selections

       Note

       In order to facilitate the use of a BladeGen model in another application (such as BladeEditor or
       ANSYS TurboGrid), you should always ensure that the model units are set. When you create a
       new BladeGen model (File > New > BladeGen Model), the default units are always “Unknown”
       (regardless of ANSYS Workbench preferences). In this case, select Model > Properties from the
       BladeGen main menu and set Model Units in the Model Property Dialog.

You can access a context menu for the Blade Design cell in the BladeGen component system by right-clicking
the cell. Most of the commands that are available are standard, and are described in Systems and Cells. The
context menu commands that are specific to the Blade Design cell are described in Table 2: Context Menu
Commands Specific to the BladeGen Blade Design Cell (p. 16).

Table 2 Context Menu Commands Specific to the BladeGen Blade Design Cell
Command                               Description
Edit                                  This command opens BladeGen. If the cell is up to
                                      date, then BladeGen will load the associated
                                      BladeGen model.
Import Existing Case                  This command opens a file browser for selecting a
                                      .bgd file. This command is only available if the cell
                                      is in the Edit Required state. If this command is not
                                      available due to having already selected a .bgd file,
                                      and you want to make the command available so


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                                                                                                                                  ANSYS BladeGen

Command                            Description
                                   that you can select a different .bgd file, then choose
                                   the Reset command in the context menu.
Create New Blade CFD Mesh This command creates a linked Mesh system and
                          generates a mesh for the associated BladeGen
                          model. This command is available only if the cell is
                          up to date.




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18                               of ANSYS, Inc. and its subsidiaries and affiliates.
ANSYS BladeEditor
ANSYS BladeEditor is a plugin for ANSYS DesignModeler for creating, importing, and editing blade geometry.
Using BladeEditor, you can create a blade from scratch. You can also import a blade from ANSYS BladeGen.
Once you have a blade in DesignModeler, you can use it as you would any geometry created in DesignModeler.
In addition, you can use BladeEditor to export the geometry for use in ANSYS TurboGrid (a meshing tool)
and Vista TF (a throughflow analysis tool).

The following topics are discussed:
 The BladeEditor User Interface
 Blade Editing Features
 Importing Blades from ANSYS BladeGen
 Loading and Modifying Blades from ANSYS BladeGen
 Using and Exporting Blades
 Configuring the BladeModeler License

The BladeEditor User Interface
The BladeEditor user interface extends the DesignModeler user interface in the following ways:

 •   There are new feature types aimed at creating a blade and flow passage.
 •   There is a set of toolbar icons, most of which are used to create the new feature types.
 •   There are new views associated with some of the feature types.
 •   There are new context menu commands associated with the new views.

The following topics will be discussed:
 Tree View and Details View
 Contour Sketch Management
 BladeEditor Toolbars
 Angle and Thickness Views
 User Preferences and Properties

Tree View and Details View
As with DesignModeler features, the primary user control of the new blade geometry features is through
the tree view and details view. The tree view shows the list of the features in the current model, and provides
a mechanism for you to select a feature for inserting, editing, or deleting. The tree view also shows the order
of operations in which DesignModeler will generate the model (top to bottom), and the feature dependen-
cies.Figure : Tree View (p. 20) shows an example of the tree view diagram with the sketches (HubContour1),
FlowPath (FlowPath1), CamThkDef (IGVCam1), and Blade (IGV) features for two blade rows.




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ANSYS BladeEditor

Figure: Tree View




You might want to temporarily suppress various features to speed up the regeneration time. This can be
                                                                                                .
managed in DesignModeler by right-clicking the feature in the tree view and selecting “Suppress” Note that
suppressing a feature also suppresses all dependent features below it. Sketches cannot be suppressed; they
can only be hidden or deleted.

When you click a contour sketch in the tree view, the sketch will be highlighted in the 3D viewer. When you
click on a camberline definition, the corresponding FlowPath layer contour will be highlighted in the 3D
viewer, and the angle and thickness views will be displayed for this definition. Any changes made to the
sketches or camberline definitions will be immediate. However, updates to the dependent FlowPath or Blade
features will happen only when you subsequently click the “Generate” button.

Contour Sketch Management
The contour sketches are managed just as normal sketches are managed in DesignModeler. To modify a
meridional contour, you should first select the sketch in the tree view and then click the “Sketching” tab to
open the sketch toolbox. If you already have the sketch toolbox open, you can select a different active sketch
from the toolbar drop-down list. For models with many different sketches, and for switching between editing
one contour or another, this could be tedious. For this reason, it is possible to modify or delete existing
edges in a sketch that is not the active sketch as long as it belongs to the same plane as the active sketch.
However, newly created edges are added only to the active sketch, so it is imperative that you have the
active sketch selected appropriately when creating new edges.



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20                                               of ANSYS, Inc. and its subsidiaries and affiliates.
                                                                                                                                    BladeEditor Toolbars

BladeEditor Toolbars
BladeEditor utilizes three separate toolbars: one for feature creation, one for selection, and one for display
control.

The following topics are discussed
 Feature Creation Toolbar
 Active Selection Toolbar
 Display Control Toolbar

Feature Creation Toolbar
The feature creation toolbar has icons for the BladeEditor specific features that can be added to the model
(and that appear in the tree view).

The following icons exist in this toolbar:

Icon                  Description
Import BGD            Creates an ImportBGD feature,
                      which is used to import a Blade-
                      Gen file and construct a solid
                      model of the blade and optionally
                      the hub and fluid zone. The flow
                      path and blade shape cannot be
                      edited in BladeEditor, but the im-
                      port can be refreshed if there are
                      any changes to the BladeGen file.
                      For details, see Importing Blades
                      from ANSYS BladeGen (p. 41).
Load BGD              Loads a BladeGen file and con-
                      structs the FlowPath, CamThkDef,
                      Blade, and Splitter features so that
                      the flow path and blade shape
                      may be edited in BladeEditor.
FlowPath              Creates a flow path (FlowPath)
                      feature, which is used to define
                      the flow path for blade geometry
                      (that is, the meridional shape of
                      the passage). For details, see
                      FlowPath Feature (p. 28).
CamThkDef             Creates a camberline/thickness
                      (CamThkDef ) feature (a blade
                      profile), which is used to construct
                      a blade geometry. For details, see
                      Camberline/Thickness Definition
                      Feature (p. 30).
Blade                 Creates a blade (Blade) feature,
                      which is used to create the blade
                      bodies. For details, see Blade Fea-
                      ture (p. 34).


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ANSYS BladeEditor

Icon                    Description
Splitter                Creates a splitter (Splitter) feature,
                        which is used to create the splitter
                        bodies. For details, see Splitter
                        Feature (p. 36).
VistaTFExport           Creates a Vista TF export (VistaTF-
                        Export) feature for exporting the
                        flow path and blade geometry to
                        the Vista TF through flow analysis
                        tool. For details, see Export to Vista
                        TF (.geo) (p. 46).
ExportPoints            Creates an ExportPoints feature
                        for exporting blade point data to
                        TurboGrid or to a meanline file.
                        For details, see Export to ANSYS
                        TurboGrid (p. 48) and Export as
                        Meanline Data (.rtzt file) (p. 47).
StageFluidZone          Creates a stage fluid zone (Stage-
                        FluidZone) feature for generating
                        the blade passage bodies. The
                        stage fluid zone is a 3D fluid re-
                        gion to support CFD analyses. For
                        details, see Stage Fluid Zone Fea-
                        ture (p. 38).
ThroatArea              Creates a throat area (ThroatArea)
                        feature for calculating the blade
                        throat area. For details, see Throat
                        Area Feature (p. 39).
Preferences             Opens the BladeEditor preferences
                        in the details view. For details, see
                        User Preferences and Proper-
                        ties (p. 25).

Note that, because of limitations in the FlowPath, CamThkDef, and Blade features, the ‘Load BGD’ feature
supports loading BladeGen files with the following restrictions:

 •   Model

     Only the ‘Angle/Thickness’ mode is supported.
 •   If loading multiple BladeGen files, the Beta Definition, ‘from Axial’ or ‘from Tangential’, must be consistent
     for all files.
 •   Layers

     Only specified span fraction layers are supported.

     The Spanwise Calculation mode must be ‘Geometric’.
 •   Angle Definition

     Only Theta and/or Beta definitions are supported, not End Angle.


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                                                                                                                                    BladeEditor Toolbars

     Only General and Ruled Element spanwise distributions are supported.

     At least one angle definition must exist on either the hub or shroud layer.

     The Angle View Data Location must be 'Meanline'.
 •   Thickness Definition

     Only the 'Normal to Meanline on Layer Surface' thickness data type is supported.

     The 'vs. Cam' and '% Cam vs. % Cam' thickness specifications are not supported.

     Only the General spanwise distribution is supported

     At least one thickness definition must exist on either the hub or shroud layer.
 •   Meridional Profile

     Only the 'Design Profile' is supported.

Active Selection Toolbar
The selection of the “active” angle and thickness view utilizes a toolbar similar to the sketch selection func-
tionality. The toolbar consists of two combo boxes: one for the FlowPath/Blade selection and one for the
layer selection. The first combo box will enable you to select from all of the currently defined FlowPath and
Blade features, while the second combo box will enable you to select from the available layers defined on
the active FlowPath.

For example, for a model that contains two FlowPath features (FlowPath1 and FlowPath2) with one Blade
feature defined on FlowPath1 and a Blade feature and Splitter feature defined on FlowPath2, the combo
box would list the following:

FlowPath1
FlowPath1 Blade1
FlowPath2
FlowPath2 Blade2
FlowPath2 Splitter2

The FlowPaths and Blades are shown separately because the CamDef feature is defined in the context of
both the FlowPath and the Blade, and therefore the view is context-specific.

Assuming there are five layers in the selected FlowPath/Blade, the Layer combo box would list the following:

Layer 1
Layer 2
Layer 3
Layer 4
Layer 5

Alternatively, if CamDef features were defined on layers 1 and 5, then the Layer combo box would list the
following:



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                                                  of ANSYS, Inc. and its subsidiaries and affiliates.                                                23
ANSYS BladeEditor

Layer 1 CamDef1
Layer 2
Layer 3
Layer 4
Layer 5 CamDef2

Display Control Toolbar
The display control toolbar enables you to control display properties such as the angle/thickness graph vis-
                                                ,
ibility and graph view actions such as “zoom fit” etc.

Angle and Thickness Views
The Angle and Thickness Views let you see and modify the Camberline/Thickness definitions. These views
have behavior similar to the views in BladeGen. Both views present the data for the active CamDef feature.
See Active Selection Toolbar (p. 23) for more details on how the active CamDef feature is selected.

If the Blade feature or any of its parent features have been modified, the curves shown in the angle/thickness
views, when displayed under the Blade feature, are updated when the model is regenerated.

The following topics are discussed:
 Angle View
 Thickness View

Angle View
The angle view displays a graph of the Theta and Beta angle definition for the selected CamDef feature.
Within this view, you can:

 •   Access a shortcut menu by right-clicking the mouse.
 •   Drag the control points defining the Theta/Beta curve (left-click on a control point and drag with the
     mouse).
 •   Change the angle type: Theta or Beta (context menu).
 •   Change the curve type (context menu).
 •   Insert or delete points (context menu).
 •   Set control point coordinates (double-click a control point and edit the coordinate values in a dialog
     box).
 •   View the coordinates of any location on a curve (hold the Ctrl key and left click any control point or
     line segment of a curve).
 •   Show all defining Theta/Beta curves in the current view (context menu).
 •   Show the second angle curve (beta or theta) in the current view (context menu).
 •   Pan the view (right-click and drag).
 •   Zoom in and out (middle-click and drag).
 •   Zoom in via a zoom box (hold the Alt key and left-click and drag from the top-left corner to the bottom-
     right corner of a rectangular region; drag in the opposite direction to re-fit the view).
 •   Change the x-axis display type: m, m’, %m, or %m’ (context menu).


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24                                                of ANSYS, Inc. and its subsidiaries and affiliates.
                                                                                                                 User Preferences and Properties

 •   Read angle data points from a file or save points to a file (context menu). In a crude way, this enables
     copying and pasting data from one CamDef feature to another, or to and from an external application,
     e.g. a spreadsheet.
 •   Convert the selected curve segment to a Bezier or spline curve of the specified order (context menu).

     Note

     When the meridional contours are changed, the angle data points are scaled relative to the percent
     m’-coordinate (% m-prime).


     Note

     X-axis value behaviour: preference used as default. Change of x-axis value will affect all layers
     viewed for a given Blade feature.

Thickness View
The thickness view displays a graph of the thickness definition for the selected CamDef feature. Within this
view, you can:

 •   Drag the points defining the thickness curve (mouse)
 •   Change the curve type: Bezier, cubic spline, piecewise-linear (context menu)
 •   Insert or delete points (context menu)
 •   Show all defining thickness curves in the current view (context menu)
 •   Zoom/Pan the view (mouse)
 •   Change the x-axis display type: m, m’, %m or %m’ (context menu)
 •   Read thickness data points from a file or save points to a file (context menu)
 •   Convert selected curve segment to Bezier or spline curve of specified order (context menu)

     Note

     When the meridional contours are changed, the thickness data points are scaled relative to the
     percent m-coordinate (% m).


     Note

     X-axis value behavior: preference used as default. Change of x-axis value will affect all layers
     viewed for a given Blade feature.


User Preferences and Properties
The model properties are listed in the details view for the root node (along with the DesignModeler file
properties.) Model properties are saved with the .agdb file. These properties include:

 •   Length Tolerance - Sketch edge tessellation tolerance in current length unit
 •   Angle Tolerance – Angle graph tolerance in degrees


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                                                  of ANSYS, Inc. and its subsidiaries and affiliates.                                        25
ANSYS BladeEditor

 •   Beta definition (axial or tangential)
 •   Angle View – x-axis type
 •   Thickness View – x-axis type
 •   Show Advanced Properties – this specifies whether the advanced parameters or expert parameters are
     shown in the details view. This only applies to specific features, such as the Blade and Splitter.

Blade Editing Features
The BladeEditor toolbar icons related to creating/editing a blade are:

Icon                  Description
FlowPath              Creates a flow path (FlowPath)
                      feature, which is used to define
                      the flow path for blade geometry
                      (that is, the meridional shape of
                      the passage). For details, see
                      FlowPath Feature (p. 28).
CamThkDef             Creates a camberline/thickness
                      (CamThkDef ) feature (a blade
                      profile), which is used to construct
                      a blade geometry. For details, see
                      Camberline/Thickness Definition
                      Feature (p. 30).
Blade                 Creates a blade (Blade) feature,
                      which is used to create the blade
                      bodies. For details, see Blade Fea-
                      ture (p. 34).
Splitter              Creates a splitter (Splitter) feature,
                      which is used to create the splitter
                      bodies. For details, see Splitter
                      Feature (p. 36).
VistaTFExport         Creates a Vista TF export (VistaTF-
                      Export) feature for exporting the
                      flow path and blade geometry to
                      the Vista TF through flow analysis
                      tool. For details, see Export to Vista
                      TF (.geo) (p. 46).
ExportPoints          Creates an ExportPoints feature
                      for exporting blade point data to
                      TurboGrid or to a meanline file.
                      For details, see Export to ANSYS
                      TurboGrid (p. 48) and Export as
                      Meanline Data (.rtzt file) (p. 47).
StageFluidZone        Creates a stage fluid zone (Stage-
                      FluidZone) feature for generating
                      the blade passage bodies. The
                      stage fluid zone is a 3D fluid re-
                      gion to support CFD analyses. For


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26                                                of ANSYS, Inc. and its subsidiaries and affiliates.
                                                                                                                       Flow Path Contour Creation

Icon                  Description
                      details, see Stage Fluid Zone Fea-
                      ture (p. 38).
ThroatArea            Creates a throat area (ThroatArea)
                      feature for calculating the blade
                      throat area. For details, see Throat
                      Area Feature (p. 39).

The following topics will be discussed:
 Flow Path Contour Creation
 FlowPath Feature
 Camberline/Thickness Definition Feature
 Blade Feature
 Splitter Feature
 Stage Fluid Zone Feature
 Throat Area Feature

Flow Path Contour Creation
The main elements of a multi-blade row machine are the flow path and the individual blade rows, as shown
in Figure : Flow Path and Blade Row Concepts (p. 27).

Figure: Flow Path and Blade Row Concepts




The first step in creating new blade row geometry is creating the flow path contours that define the hub,
shroud, inlet and outlet. The flow path contours are defined by sketch edges, which can be created using
the existing DesignModeler sketch tools. Each contour (hub, shroud, etc.) should be defined in a separate
sketch. This implicitly identifies all the edges belonging to a given contour. All contour sketches are expected
to lie on the same Plane feature. Not only will this guarantee that the contours are coplanar, it will enable
you to apply constraints and dimensions between sketches.




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                                                 of ANSYS, Inc. and its subsidiaries and affiliates.                                          27
ANSYS BladeEditor


     Note
      •    Contour sketches must be created on the (global) ZX-plane. The local X and Y axes on the
           sketch plane correspond to the global Z and X axes, respectively. The local X axis corresponds
           to the machine axis and the local Y axis corresponds to the radial coordinate axis. Con-
           sequently, all flow contours in the sketch must have positive Y coordinates.
      •    It is advisable that you turn off the sketch global autoconstraint setting. Click the Sketching
           tab, click the Constraints toolbox, click Auto Constraints and clear the Global check box.
           Having this global constraint turned on may cause undesirable constraints to be added to
           the LayerContour edges.
      •    The hub, shroud, inlet, and outlet contour end points must be coincident.


FlowPath Feature
The FlowPath feature specifies the flow path. The contour sketches described in Flow Path Contour Cre-
ation (p. 27) are used in the definition of this feature. The FlowPath feature also creates the constant-span-
fraction layers used to define the blade profiles, and automatically creates the LayerContour sketch, which
shows the locations of the layers. The feature properties are listed in the table below. Note that all items
under each bold heading in the table are grouped under that heading.

Details of [Feature Name]
FlowPath               [Name]
Machine Type           [Pump | Centrifugal Compressor |
                       Axial Compressor | Fan | Radial
                       Turbine | Axial Turbine | Hydraulic
                       Turbine | Other | Undefined]
Theta Direction        [Right-handed | Left-handed]
Hub Contour            [Sketch selection]
Shroud Contour         [Sketch selection]
Inlet Contour          [Sketch selection]
Outlet Contour         [Sketch selection]
Hub Cut?               [Yes | No]
(If Hub Cut = Yes)     [Sketch selection]

Hub Cut
Shroud Cut?            [Yes | No]
(If Shroud Cut =       [Sketch selection]
Yes)
Shroud Cut
Number of Layers       Implicitly defined number of layers
Layer: 1
Layer Type             Fixed Span
Span Fraction          0
Layer: 2


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                                                                                                                                   FlowPath Feature

Layer Type           Fixed Span
Span Fraction        [0 < Value < 1]
Layer: 3
Layer Type           Fixed Span
Span Fraction        [0 < Value < 1]
Layer: 4
Layer Type           Fixed Span
Span Fraction        1

The Machine Type is used by downstream applications, for example in CFD-Post, for determining the appro-
priate default post-processing report. The Theta Direction specifies the interpretation of the theta direction
for the CamDef angle definitions. The theta direction can be specified as either right-handed or left-handed
relative to the direction of the global z-axis (the machine axis).

By default, the flow path starts with two layers: one for the hub and one for the shroud. You can insert or
delete layers using a shortcut menu in the details view. Layers on which CamDef features are defined cannot
be deleted. The first and last layers must be at span fractions of 0 and 1, respectively; these will always be
created and cannot be deleted or changed. A given blade does not need to have defined profiles on all
layers. The layers are defined in the context of the FlowPath feature for consistency between blade rows.

The only Layer Type in version 12 is Fixed Span. This requires that you specify the span fraction for the given
layer.

You can create the FlowPath feature automatically via a BladeGen import, or manually. In either case, you
can change the sketch selections once the feature has been created. You must ensure that the contours are
properly connected to form a closed loop. This means that the endpoints of adjacent contours must be co-
incident.

In the tree view, the parent sketches (HubContour, ShroudContour, etc.) and child sketch (LayerContour)
should appear as sub-features of the FlowPath feature. These sketches will also appear under the parent
meridional plane.

The following topic will be discussed:
 Flow Cut

Flow Cut
The FlowPath feature has optional hub cut and shroud cut properties to support trimming the flow path
for a 'flow cut'. An example is if you have a base centrifugal compressor blade design that is used for a range
of compressors. In this case, the FlowPath and Blade features would define the base blade geometry. You
then wish to use the same blade but in a different size compressor, so the blade height needs to be trimmed.
The flow cut would be used to define the final flow path boundaries, and would trim the height of all blades
in the flow path.

The flow cut affects all blades that reference the flow path. The flow cut properties take as input the sketch
contours that define the flow cut. The additional feature properties are in a group below the Outlet Contour
property. The property group is defined below.

To make best use of this feature, sketches should support the reading of external point data, in particular
point data exported from CFD-Post. This lets you choose a flow “streamline” from a Vista TF or CFX analysis



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ANSYS BladeEditor

and use it to trim the flow path. Currently, creating spline curves from external point data is only supported
via script.

Camberline/Thickness Definition Feature
The Camberline/Thickness Definition (CamDef ) feature provides the angle and thickness distribution on a
selected layer contour. This definition is a child of the FlowPath feature and a parent of the Blade feature.
The angle and thickness distributions are specified versus normalized coordinates corresponding to 0% at
the leading edge and 100% at the trailing edge. A CamDef feature can be referenced by more than one
Blade feature. Also, a CamDef feature can be copied from one layer to another.

Each CamDef feature will appear as a sub-feature of the parent FlowPath in the tree view. When a CamDef
feature is referenced by a Blade, it will also appear as a sub-feature for that Blade. This is consistent with
the tree view behavior for sketches, which provide a similar function to the CamDef features.

The CamDef feature properties are as follows:

Details of [Feature Name]
Camberline Defini-    [Feature Name]
tion
Flow Path             [FlowPath feature selection]
Layer Number          [Index Value]
Camberline Details
Angle Definition?     [Yes | No]
Angle Definition      [Theta | Beta]
Type
(For Beta defini-     [Leading Edge | Trailing Edge]
tion only)

Theta Reference
Theta @ LE            [Value]

or

Theta @ TE            [Value]
Angle Data Loca-      [Camberline | Side 1 | Side 2]
tion
[Parameter List]      [Parameter Values]
Thickness Details
Thickness Defini-     [Yes | No]
tion?
Thickness Defini-     [Normal to Cambersurface | Nor-
tion Type             mal to Camberline on Layer sur-
                      face | Tangential on Layer surface]

The angle and thickness data that is associated with a CamDef feature is displayed in the angle/thickness
graph view.




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30                                                of ANSYS, Inc. and its subsidiaries and affiliates.
                                                                                                  Camberline/Thickness Definition Feature




The CamDef feature saves the angle data as % m-prime and the thickness data as % m. After a CamDef is
applied to the portion of a layer between LE and TE of a blade/splitter, the local angle data and thickness
data are created for the blade/splitter. These local data are represented as m-prime and m values which are
converted from % m-prime and % m.

If the Angle Definition Type is set to Theta, then the specified angle curve is used as the theta definition for
the camberline. If the Angle Definition Type is set to Beta, then the angle curve is used as the Beta definition,
and the theta definition is derived by integrating the Beta curve with the specified Theta Reference. The
Theta Reference can be specified at either the leading edge or the trailing edge of the blade for which the
camberline is applied.

When a CamDef feature is selected on the feature tree, its angle data will be displayed on the angle graph
and its thickness data will be displayed on the thickness graph.

When the data in angle or thickness graph pane is modified, the data inside the CamDef feature will be
changed to reflect the modification. Also, if any blade/splitter refers to the CamDef feature, all these
blade/splitter should update their local angle/thickness data.

If you select 'No' for the Angle Definition or Thickness Definition parameter, then no curve data for this
definition will be available for editing in the graph view, and this definition will be ignored in the corres-
ponding angle or thickness surface calculation. Furthermore, if the selected CamDef feature is a sub-feature
to a Blade, then the graph view will show the interpolated angle or thickness data for this blade, otherwise


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ANSYS BladeEditor

no data will be shown in the graph. The interpolated data is for display only and cannot be edited; the
context menu commands for editing are hidden in this case.

If you subsequently select 'Yes' for the Angle Definition or Thickness Definition parameter, then the curve
data will be initialized by interpolation if possible, otherwise it will be initialized to default data (two points).
Interpolation will occur if the selected CamDef feature is a sub-feature to a Blade, so that the data can be
interpolated from the blade definition. If the CamDef feature is reference by more than one blade, then the
blade that is selected (above the CamDef feature) will be used to interpolate the data.

If you want to insert a CamDef feature into an existing Blade feature without initially affecting the shape of
the blade, the ‘Insert/Interpolate Camberline’ operation can be used. Multi-select a new CamDef feature
along with the Blade feature, right-click, and select ‘Insert/Interpolate Camberline’. The angle and thickness
data of the selected CamDef feature will then be updated by interpolating from the existing blade.

If you specify a curved leading or trailing edge contour, you must have at least three angle and/or thickness
defining camberlines to create the desired blade shape. Furthermore, if you specify a cut-off leading or
trailing edge and you do not have sufficient camberlines to follow the edge curvature, then the cut-off op-
eration will fail. Adding additional camberline definitions (especially where the leading/trailing edge curve
deviates the most from the blade shape) should fix this problem.

The following topics are discussed:
 Importing and Exporting Angle Definition Data
 Importing and Exporting Thickness Definition Data
 Converting Curves to Bezier or Spline
 Converting Angle Definition Data
 Forcing Interpolation of the Definition Data

Importing and Exporting Angle Definition Data
There is an import/export points mechanism for the Angle Definition to support the manipulation of the
Angle Definition points outside of BladeEditor, and to provide a means to read data from a file produced
externally. In the Angle View, the context menu operation 'Read Points' lets you replace the active curve
data points from the data in a text file called a '.ha' file. The context menu operation 'Save Points' lets you
save the active data points to a '.ha' text file. These options are available only if the Angle Definition is active,
i.e. set to 'Yes'.

The first line in the '.ha' file specifies the number of points. Subsequent lines in the file, one for each data
point, contain the point coordinate values 'h, a', where 'h' is the horizontal or x-axis value and 'a' is the angle
value. The point coordinates correspond to the defining points for the angle definition curve, which may
be either Theta or Beta, in degrees, versus m-prime, % m-prime, m or % m.

When reading the '.ha' file, the data point coordinates will be interpreted based on the Angle Definition
Type and the selected x-axis type. If the Angle Definition Type is set to Theta, then the angle values will be
interpreted as Theta values. Otherwise, the angle values will be interpreted as Beta values. If the x-axis is
set to m-prime or % m-prime, then the 'h' coordinates for the data points will be treated as % m-prime values,
and the values will be normalized based on the first and last data points so that the values start at zero and
end at 100%. If the x-axis is set to m or % m, then the 'h' coordinates for the data points will be converted
to m values by normalizing based on the first and last data points and then multiplying by the maximum
m on the layer. These values will then be converted to % m-prime. The existing angle curve data for all
segments will be replaced by a single curve segment with the data from the '.ha' file, and the curve type
will be set to 'cubic spline'.

When you choose 'Save Points', the defining points for all curve segments will be written sequentially to
the file starting with the leading edge point and ending at the trailing edge point. The 'h' coordinates will

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32                                                 of ANSYS, Inc. and its subsidiaries and affiliates.
                                                                                                  Camberline/Thickness Definition Feature

be written in the value corresponding to the selected x-axis type. If the Angle Definition Type is set to Theta,
then the Theta values will be written as the angle values. Otherwise, the Beta values will be written as the
angle values.

You can select the x-axis scale as m-prime, m, or % m only if the selected CamDef feature is defined in the
context of a Blade feature.

Importing and Exporting Thickness Definition Data
There is an import/export points mechanism for the Thickness Definition to support the manipulation of the
Thickness Definition points outside of BladeEditor, and to provide a means to read data from a file produced
externally. In the Angle View, the context menu operation 'Read Points' lets you replace the active curve
data points from the data in a text file called a '.ht' file. The context menu operation 'Save Points' lets you
save the active data points to a '.ha' text file. These options are available only if the Thickness Definition is
active, i.e. set to 'Yes'.

The first line in the '.ht' file specifies the number of points. Subsequent lines in the file, one for each data
point, contain the point coordinate values 'h, t', where 'h' is the horizontal or x-axis value and 't' is the
thickness value. The point coordinates correspond to the defining points for the thickness definition curve
in the length unit being used in DesignModeler, versus m-prime, % m-prime, m or % m.

When reading the '.ht' file, the data point coordinates will be interpreted based on the selected Thickness
Definition Type and the x-axis type. If the x-axis is set to m or % m, then the 'h' coordinates for the data
points will be treated as % m values, and the values will be normalized based on the first and last data
points so that the values start at zero and end at 100%. If the x-axis is set to m-prime or % m-prime, then
the 'h' coordinates for the data points will be converted to m-prime values by normalizing based on the first
and last data points and then multiplying by the maximum m-prime on the layer. These values will then be
converted to % m. The existing thickness curve data for all segments will be replaced by a single curve
segment with the data from the '.ht' file, and the curve type will be set to 'cubic spline'.

When you choose 'Save Points', the defining points for all curve segments will be written sequentially to
the file starting with the leading edge point and ending at the trailing edge point. The 'h' coordinates will
be written in the value corresponding to the selected x-axis type, while the thickness coordinates will be
written in the value corresponding to the selected Thickness Definition Type.

You can select the x-axis scale as m-prime, m, or % m only if the selected CamDef feature is defined in the
context of a Blade feature.

Converting Curves to Bezier or Spline
This feature lets you convert a curve segment in either the Angle or Thickness views to an equivalent spline
or Bezier curve with a specified number of points. The new curve is an approximation of the original curve,
and the error in the approximation depends on the complexity of the original curve and the specified
number of points for the new curve. This operation is very helpful for simplifying a curve with many points,
either because it was imported or was interpolated.

The context menu items are: 'Convert to Bezier' and 'Convert to Spline'. They are available in both the Angle
and Thickness views. When choosing either of these options, you are asked to specify the number of points
for the new curve in a dialog box. After clicking OK, you are required to select the curve segment to convert
in the graph view. The curve will be converted immediately following your selection.




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ANSYS BladeEditor

Converting Angle Definition Data
If you select the CamDef feature at the root tree level and change the Angle Definition Type, e.g. to Beta
from Theta, then the input data in the graph will be kept as is, and will be taken as the data for the new
angle type. If you switch from Theta to Beta, the Theta reference will be defaulted to zero. This switch will
likely change the shape of the camberline.

If you select the CamDef feature under a Blade feature and change the Angle Definition Type, then the angle
data is converted to the new type. This conversion will try to retain the shape of the camberline by interpol-
ation. Thirty points are used in the interpolated curve.

Forcing Interpolation of the Definition Data
You may want to insert a CamDef feature into an existing blade without initially changing the shape of the
blade. In this case an interpolation is required. You should multi-select the CamDef feature to be inserted
                                                                                 .
along with the Blade feature, and right-click “Insert and interpolate Camberline” This would insert the
CamDef feature into the selected Blade and re-initialize the data from the angle and thickness definitions.
Which angle data to be interpolated would be determined by the Angle Definition Type in the CamDef
feature. The selected CamDef feature cannot be referenced by another blade.

Blade Feature
The Blade feature is the geometry feature that is responsible for creating a blade or blade set. This feature
defines the key properties of the blade, such as the blade type and the leading and trailing edge location
and shape. It references the angle and thickness definitions to define the blade profiles. A given Blade feature
(and its child Splitter features) must not overlap with other Blade features (and their child Splitter features)
within a given FlowPath.

The feature properties are as follows:

Details of [Feature Name]
Blade                 [Feature Name]
Camberline Defini-    [CamDef selections]
tions
Type                  [Rotor | Stator]
Number of Blade       [Int Value]
Sets
Surface Construc-     [General | Ruled Element]
tion
Blade Extension       [Value]
(%)
Leading Edge Details
Contour               [Sketch selection]
Type                  [Ellipse | Cut-off | Square]a
Ratio at Hub (for     [Value]
Ellipse only)
Ratio at Shroud       [Value]
(for Ellipse only)
Trailing Edge Details

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34                                                of ANSYS, Inc. and its subsidiaries and affiliates.
                                                                                                                                          Blade Feature

Contour                     [Sketch selection]
Type                        [Ellipse | Cut-off | Square]
Ratio at Hub (for           [Value]
Ellipse only)
Ratio at Shroud             [Value]
(for Ellipse only)
Advanced Properties (Hidden by default)
Number of Points            [Int Value]
Along the Blade
Number of Points            [Int Value]
for LE (for Ellipse
only)
Number of Points            [Int Value]
for TE (for Ellipse
only)
Camberline/Thickness Definitions: [number]
Camber/Thick Def.           [CamDef reference]
1
Camber/Thick Def.           [CamDef reference]
2
a
 Note that you cannot specify a perfectly sharp trailing edge. As a workaround, you can specify a square trailing edge with a small, but finite,
thickness (for example, 0.05 mm).

The Type property specifies whether the blade is a rotating or stationary component. The FlowPath selection
is the reference to the FlowPath feature, which is mandatory. The CamDef selections are the references to
the CamDef features that describe the angle and thickness definitions; these are also mandatory. At least
one CamDef with a specified angle definition must be selected to define the Blade. If only one angle defin-
ition is specified, the angle definition must be given on either the hub or the shroud. The same rule applies
                                                                            ,
for the thickness. If the Surface Construction type is set to “Ruled Element” then only two CamDefs may be
selected, and they must be defined at the hub and shroud. Once the CamDefs have been selected, they will
appear (for reference only) under the section at the bottom of the list "Camberline Definitions".

In the tree view, CamDef features appear as sub-nodes of the Blade/Splitter feature.

When the CamDef feature is highlighted from the sub-node position of Blade/Splitter feature, the angle
curve and thickness curve can be displayed as percentage M/Mp values and actual Mp/M values based on
current blade/splitter.

When the curve in angle or thickness graph pane is modified, the CamDef feature is updated simultaneously.
The display for blades/splitters referring to the CamDef feature may not be updated until the generation is
finished.

If you want to insert a CamDef feature into an existing Blade feature without initially affecting the shape of
the blade, the ‘Insert/Interpolate Camberline’ operation can be used. Multi-select a new CamDef feature
along with the Blade feature, right-click, and select ‘Insert/Interpolate Camberline’. The angle and thickness
data of the selected CamDef feature will then be updated by interpolating from the blade definition.




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ANSYS BladeEditor

Splitter Feature
This feature creates a new blade relative to an existing (main) blade such that the new blade (or splitter)
shares the same Flow Path and blade count, and is generally assumed to be part of the same blade row.
The base object of this feature is the selected Blade feature; only one Blade feature can be selected per
Splitter feature.

The Splitter feature can be one of two forms: a cloned splitter or an independent splitter. The form is specified
in the feature properties. Once the feature has been created, you cannot change the type.

The following topics will be discussed:
 Cloned Splitter
 Independent Splitter

Cloned Splitter
A cloned splitter shares the same blade shape as the main blade, but is offset in theta from the main blade.
Typically, a cloned splitter is trimmed by the BladeTrim feature to shorten the blade, e.g. the splitter in a
centrifugal compressor.

The feature properties are as follows:

Details of [Feature Name]
Splitter               [Feature Name]
Type                   Cloned
Main Blade             [Blade feature selection]
Offset Type            [Pitch Fraction | Specified Angle]
Pitch Fraction         [Value: 0-1]

or

Angle                  [Value]

The Offset Type specifies how the splitter will be offset relative to the main blade. If “Specified Angle” is
selected, then the angular offset of the cloned splitter blade relative to the main blade is specified directly.
If “Pitch Fraction” is selected, then the pitch fraction as a value between 0 and 1 is specified. The pitch
fraction represents the fraction of distance between two adjacent main blades. The actual angular offset is:

offset = pitch fraction * 2 * pi / n

where n is the number of main blades.

Independent Splitter
An independent splitter can have a completely different shape than the main blade, but it still shares the
same blade count and has a fixed offset from the main blade. The feature properties are nearly identical to
the Blade feature except for the additional main blade reference and offset value.

The properties are as follows:

Details of [Feature Name]


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36                                                 of ANSYS, Inc. and its subsidiaries and affiliates.
                                                                                                                                     Splitter Feature

Splitter               [Feature Name]
Type                   Independent
Main Blade             [Blade feature selection]
Offset Type            [Pitch Fraction | Specified Angle]
Pitch Fraction         [Value: 0-1]

or

Angle                  [Value]
Offset Reference       [Hub at Leading Edge | Hub at
(Only for Pitch        Trailing Edge]
Fraction)
Camberline Defini-     [CamDef selections]
tions
Surface Construc-      [General|Ruled Element]
tion
...

(the remaining details are the same as for the Blade
feature)

The interpretation of the Offset Type is different for an independent splitter than for the cloned splitter. If
“Specified Angle” is selected, then the angular position of the splitter will be determined by the camber
surface theta, shifted by the specified angle. If “Pitch Fraction” is selected, then you enter the pitch fraction
as a value between 0 and 1, for the cloned splitter. However, because an independent splitter can have a
different shape than the main blade, an Offset Reference must be specified. This determines how the splitter
will be positioned relative to the main blade. The angular offset and the offset reference determine the ref-
erence theta for the splitter blade.

When “Hub at Leading Edge” is selected for the Offset Reference, the reference theta and the camberline
locations are calculated as follows:

 1.    An offset reference meridional location is calculated at the intersection of the hub contour and the
       splitter leading edge contour.
 2.    For the offset meridional location, the main blade theta value is calculated from the main blade cam-
       bersurface.
 3.    The reference theta is then calculated by adding the angular offset (from the pitch fraction or specified
       angle) to the main blade theta value.
 4.    All splitter camberline theta values are offset internally so that the splitter hub camberline starts at
       the reference theta.

Alternatively, when “Hub at Trailing Edge” is selected for the Offset Reference, the reference theta and the
camberline locations are calculated as follows:

 1.    An offset reference meridional location is calculated at the intersection of the hub contour and the
       splitter trailing edge contour.
 2.    For the offset meridional location, the main blade theta value is calculated from the main blade cam-
       bersurface.



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ANSYS BladeEditor

    3.   The reference theta is then calculated by adding the angular offset (from the pitch fraction or specified
         angle) to the main blade theta value.
    4.   All splitter camberline theta values are offset internally so that the splitter hub camberline ends at the
         reference theta.

When a BladeGen model with splitters is imported, the theta values shown for the splitter camberlines may
appear to differ in BladeEditor. The reason is that BladeGen always calculates the splitter reference theta
using a meridional location at the main blade leading edge rather than at the splitter blade leading edge.
When the splitter camberline definitions are imported they are converted to preserve the blade position
and shape, and therefore the point data for the definitions may differ.

Stage Fluid Zone Feature
The “fluid zone” represents the 3D fluid region within the flow passage, and is used to define the extent of
the CFD domain. In release 11.0, a fluid zone was automatically created for each ImportBGD feature, which
included the fluid region around a single blade row. For multiple blade rows, the fluid zone must include
separate regions for, and have distinct interfaces between, each blade row.

In release 12.0, a new StageFluidZone feature takes as a reference the selected FlowPath feature, and creates
solid bodies for the fluid region in every blade row of the flow path. The first stage fluid zone in the flow
path will start at the inlet contour and extend to the first interface (or to the outlet contour if there is only
one blade row). The last stage fluid zone starts at the last interface and extends to the outlet contour. All
intermediate stage fluid zones start and end at the interfaces adjacent to the blade row. The individual
bodies are “frozen” so that they are not merged to adjacent solid bodies, including adjacent stage fluid zone
bodies. (Individual bodies can be suppressed or hidden using existing DM functionality.) The StageFluidZone
feature respects any BladeClearance, BladeTrim, or FlowCut features that have been applied to the FlowPath
or blade rows prior to the StageFluidZone feature. All active bodies (blades, hub, etc.) are subtracted from
the fluid zone.

The stage fluid zone upstream and downstream interfaces are located by default halfway between the closest
extents of the adjacent blade rows. For this to work, the StageFluidZone feature assumes that there is no
overlap between adjacent blade rows; the StageFluidZone feature reports an error if this condition is violated.
(Overlapping blade designs should be created using a combination of the Blade and Splitter features.) You
may adjust the relative location of the interface by using one value in the range 0-1.

The feature properties are as follows:

Table 1 Details View for StageFluidZone Feature
Details of [Feature Name]
StageFluidZone             [Feature Name]
Flow Path                  [FlowPath feature selection]
Create Named Se-           [Yes | No]
lections
Interface Detail 1:
Interface Location         [Value: 0-1, default 0.5]a
Interface Detail 2:
Interface Location         [Value: 0-1, default 0.5]a
a
 0 corresponds to the aftmost trailing edge of the set of blades in the upstream blade row. 1 corresponds to the foremost leading edge of
the set of blades in the downstream blade row.


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38                                                     of ANSYS, Inc. and its subsidiaries and affiliates.
                                                                                                                                    Throat Area Feature

The Create Named Selections property determines whether the feature will automatically create named se-
lections for each stage fluid zone. The Interface Details groups are created dynamically depending on the
number of interfaces involved (number of blade rows less one.)

Named selections are created automatically for each blade row of the StageFluidZone. The naming convention
is Hub_[Main Blade Name], Shroud_[Main Blade Name], Blade_[Blade Name], etc. where Main Blade Name
is the name of the main blade in the given blade row. For the Blade_ regions, each blade in the blade row
will have a separate region defined.

Named selections will not appear in DesignModeler, but they will appear if you load the .agdb file into the
Mechanical application or the Meshing application, provided that you have set the properties of the Geometry
cell (on the Project Schematic page in ANSYS Workbench) as follows:

 •   Attributes is selected.
 •   Attribute Key string is cleared.

     (This setting appears when Attributes is selected.)
 •   Named Selections is selected.

You can make the Geometry cell settings this way by default by selecting Tools > Options from the ANSYS
Workbench main menu, browsing to the Geometry Import branch, and setting CAD Attributes (same as At-
tributes), CAD Attributes > Filtering Prefixes (same as Attribute Key), and Named Selections.

     Note

     If the StageFluidZone periodic interfaces do not appear to be trimmed appropriately on the hub
     or shroud boundaries, you can try increasing the Blade Extension property for the corresponding
     blade feature to remedy the problem. The StageFluidZone feature uses this property to control
     how the periodic interfaces are created.


Throat Area Feature
The throat area (ThroatArea) feature is used to calculate and display the throat surface(s) for one or more
selected blade rows. The calculation is normally updated each time you issue the Generate command. The
feature may be suppressed to avoid the calculation time when it is not needed, or the feature may be deleted
if it is no longer needed.

The feature properties are as follows:

Table 2 Details View for ThroatArea Feature
Details of [Feature Name]
ThroatArea            [Feature Name]
Blade                 [Blade feature selection]
Location              [Leading Edge | Trailing Edge |
                      Minimum Area]
Throat Surface Ex-    [Value]
tension

(Advanced Prop-
erty)

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ANSYS BladeEditor

Throat Details:
Area                    [Value]
Layer 1 Length          [Value]
Layer 2 Length          [Value]
...
...
...

Blade items are
listed for all selec-
ted blades.

The input property, Blade, is a Blade feature selection used to indicate the blade row. The Location property
specifies the region for which to calculate the passage area. The choices are as follows:

 •    Leading Edge - computes the passage area in the region of the main blade leading edge.
 •    Trailing Edge - computes the passage area in the region of the main blade trailing edge.
 •    Minimum Area - computes the minimum passage area considering all blades in the blade row.

The Leading Edge option can report the throat width for a throat location that is a considerable distance
away from the leading edge. A similar statement applies for the Trailing Edge option.

The minimum area calculation uses a minimization algorithm based on the blade profiles on the design
layers of the blade. If there are only one or two defining layers, then additional layers will be inserted for
the purpose of the calculation.

The output property group contains the throat area and the throat lengths for each layer defined in the
flow path.

The throat surface is displayed in the viewer as a frozen sheet body. The Throat Surface Extension property
enables you to control the surface extension to ensure that the throat surface is cut by the blade bodies
properly. This is an advanced property and it is shown only if the Show Advanced Properties preference is
selected.

       Note

       The minimization calculation of the throat surface area uses the raw blade profile data from the
       Blade feature and not the final solid model. The actual throat surface area is calculated from the
       solid model.


       Note

       For Vista TF users: The throat widths are not added to the Vista TF geometry file. The throat data
       can be added manually. See the .geo file format description in Specification of the Geometry Data
       File (*.geo) (p. 83).




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40                                                  of ANSYS, Inc. and its subsidiaries and affiliates.
                                                                                                    Importing Blades from ANSYS BladeGen


Importing Blades from ANSYS BladeGen
BladeEditor provides a geometry connection between BladeGen and DesignModeler. Reasons for importing
BladeGen blades into DesignModeler include:

 •   ANSYS BladeGen can output geometry in many different point data formats, but its surface output in
     IGES format is cumbersome to use.
 •   BladeGen does not produce a solid model in a standardized format such as Parasolid.
 •   You can combine an imported blade with other CAD geometry imported via one of the many Design-
     Modeler-supported CAD file formats.

Through BladeEditor, one or more BladeGen models can be linked into a DesignModeler session, so that
any changes to the BladeGen models will be reflected in DesignModeler the next time you update the
Geometry cell.

When you import a BladeGen model, BladeEditor does the following:

 •   constructs blade surfaces
 •   creates a solid model for the blades and hub
 •   creates 2-D sketches for the meridional contours and non-flow-path hub geometry
 •   creates periodic fluid zones

The preferred method of importing a BladeGen file is to create a link from the Blade Design cell of a BladeGen
system to the Geometry cell. This link maintains the data transfer relationship between the two cells. The
desired import options should be set in the Blade Design cell properties. (See Table 1: BladeGen Blade Design
Cell Properties (p. 14) for more information.) After you make the link, the Geometry cell should be updated
to process the imported geometry.




     Note

     If you edit the Geometry cell before updating it, then the Import BGD feature details that are
     shown in BladeEditor may not accurately reflect the Blade Design cell properties. To refresh the

     Import BGD feature properties, click           in BladeEditor. It is not recommended that you
     edit the Import BGD properties inside BladeEditor because they will be overwritten by the prop-
     erties from the Blade Design cell the next time you update the Geometry cell.


Alternatively, you can import a BladeGen file from outside the project. To do this, click                 in the
BladeEditor toolbar. When you click this icon, you will be prompted for the location and name of the
BladeGen (.bgd) file. Once the filename is selected, the details view will let you select the properties for
the import. These properties are listed in Table 3: Properties for the Import BGD File Feature (p. 42). As with




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                                                  of ANSYS, Inc. and its subsidiaries and affiliates.                                41
ANSYS BladeEditor

other DesignModeler feature properties, you can double-click in a property value box to change the selection
to the next choice, or single-click on the property and select the value from the drop-down list.

Table 3 Properties for the Import BGD File Feature
Property       Default              Function
               Value
ImportBGD      ImportBGD#           This property defines name of the import feature.
Source         (selected            This property defines the name and path of the imported
               BGD File)            .bgd file. You can change the source to a new .bgd file
                                    if Refresh is set to Yes.
Unit Prefer-   (default is          You may change the value of this property to the intended
ence           the Design-          BladeGen model length unit if the latter does not match
               Modeler              the DesignModeler length unit. If the BladeGen model
               length unit)         length unit is specified as “Unknown” (in the BladeGen
                                    model properties), then BladeEditor will interpret the
                                    model as having the length unit specified here, and will
                                    process the model by converting from this unit into the
                                    DesignModeler length unit. Otherwise, the unit specified
                                    here will be ignored, and the model will be converted from
                                    the unit specified in the .bgd file into the DesignModeler
                                    length unit. It is recommended that you specify a length
                                    unit in BladeGen so that this information is stored in the
                                    .bgd file.

                                    Make sure that the length unit specified here is appropriate
                                    for the model. If the BladeGen dimensions are too small,
                                    DesignModeler may fail to import the BladeGen model.
Create Hub     Yes                  If this property is set to Yes, then BladeEditor will create
                                    a HubProfile sketch for the non-flow path hub geometry,
                                    and will create a revolved body feature called HubBody.
Hub Offset     1 (Inch)             This property defines the default line offset (in the preferred
                                    length unit) for creating the initial HubProfile sketch.

                                    Note that this property is available only if Create Hub is
                                    set to Yes.
Create         All                  If this property is set to All, then BladeEditor will create
Blades                              all the blades using the number of blades specified in the
                                    BladeGen model.

                                    If this property is set to 1, then only the first blade will be
                                    created.
Merge Blade    Yes                  If this property is set to No, then BladeEditor will create the
Topology                            blade with four faces corresponding to the leading edge,
                                    pressure side, trailing edge and suction side. This can make
                                    it easier to create a structural mesh for the blades in the
                                    Mechanical application.

                                    If this property is set to Yes, then the blade faces will be
                                    merged where they are tangent to one another.


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42                                               of ANSYS, Inc. and its subsidiaries and affiliates.
                                                                                                   Importing Blades from ANSYS BladeGen

Property       Default              Function
               Value
Blade Loft     Streamwise           If this property is set to Streamwise, then BladeEditor
Direction                           will loft the blade surfaces in the streamwise direction
                                    through curves that run from hub to shroud. This is the
                                    default because the surface is more well defined, especially
                                    for flank-milled blades.

                                    If this property is set to Spanwise, then BladeEditor will
                                    loft the blade surfaces in the spanwise direction through
                                    the blade profile curves.
Create         No                   This property specifies whether a shroud clearance is cre-
Shroud                              ated. If No is selected, then no shroud clearance is created.
Clearance                           To create a shroud clearance, choose either Relative
                                    Layer or Absolute Layer. The blade(s) will be trimmed
                                    off at the selected BladeGen output layer, and the layer
                                    contour will be created in the LayerProfile sketch.

                                    If Relative Layer is selected, then the selected Layer
                                    Number is relative to the shroud layer, e.g., 1 implies the
                                    first layer closest to the shroud layer, 2 implies the second
                                    closest layer to the shroud, etc.

                                    If Absolute Layer is selected, then the selected layer
                                    index counts up from the hub layer, which is zero.
Layer Num-     1                    This property defines the selected layer index for the shroud
ber                                 clearance.

                                    Note that this property is available only if Create Shroud
                                    Clearance is selected.
Create Fluid   Yes                  If this property is set to Yes, then BladeEditor will create
Zone                                a StageFluidZone body for the flow passage, and an
                                    Enclosure feature to subtract the blade body. The resulting
                                    Enclosure can be used for a CFD analysis of the blade pas-
                                    sage.
Create         Yes                  If this property is set to Yes, then BladeEditor will create
Named Se-                           NamedSelections (regions) for the typical faces of the
lections                            blade passage, i.e., Blade, Hub, Shroud, Inflow, Out-
                                    flow, PeriodicA and PeriodicB. These NamedSelec-
                                    tions can be used as selection groups in other ANSYS
                                    Workbench applications, e.g., as regions in CFX-Mesh.

                                    Note that this property is available only if Create Fluid
                                    Zone is set to Yes.
Blade Exten-   2                    This property defines the surface extension length (as a
sion (%)                            percentage of the average hub to shroud distance) for the
                                    blade surfaces. These surfaces are extended and then
                                    trimmed to the MasterProfile sketch to ensure that
                                    the blade solid correctly matches the hub and shroud
                                    contours.


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                                                 of ANSYS, Inc. and its subsidiaries and affiliates.                                43
ANSYS BladeEditor

Property           Default              Function
                   Value
Periodic Surf      5                    This property defines the surface extension length (as a
Extension                               percentage of the average hub to shroud distance) for the
(%)                                     periodic surfaces. These surfaces are extended to ensure
                                        that the StageFluidZone is properly cut.
Periodic Surf      Three Pieces         This property specifies the style of the periodic interface
Style                                   surfaces.

                                        If Three Pieces is selected, then the periodic surface is
                                        created in three connected pieces: one upstream of the
                                        blade, one within the passage, and one downstream of the
                                        blade. This style can better accommodate highly curved or
                                        twisted blades, and is similar to the ANSYS TurboGrid style
                                        of periodic surface.

                                        If One Piece is selected, then the periodic surface is cre-
                                        ated as a single surface.

                                        Note that this property is available only if Create Fluid
                                        Zone is set to Yes.
Refresh            Yes                  This property specifies whether the imported BladeGen
                                        model should remain linked to the DesignModeler session.
                                        If this property is set to Yes, then when the DesignModeler
                                        Generate button is clicked, BladeEditor will check to see if
                                        the BladeGen file has changed. If the BladeGen file has been
                                        modified, BladeEditor will reload the file. If the BladeGen
                                        file has moved or has been deleted, BladeEditor will switch
                                        this property to No and will leave the blade geometry un-
                                        changed.

                                        If this property is set to No, then BladeEditor will not reload
                                        the BladeGen file when the DesignModeler model is regen-
                                        erated.

Once these properties have been set, click the Generate button, and the BladeGen model will be imported.

The following features will then be created in the tree view:

    •   MerPlane: this plane is a copy of the Z-X plane; it is the plane on which the blade design sketches
        are created.
        –   MasterProfile: a sketch defining the hub, shroud, leading edge, trailing edge, inflow and outflow
            boundaries of the blade passage (imported from the .bgd file) will be created. This sketch is used
            during the creation of the blade bodies, and can be used to create the fluid zone. You should not
            modify this sketch.1
        –   BladeProfile: a sketch defining the locations of the leading and trailing edges for the main
            blade will be created.



1
 This constraint is to prevent the MasterProfile and the blades from becoming inconsistent, because the blade surface data
comes from BladeGen.

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44                                                   of ANSYS, Inc. and its subsidiaries and affiliates.
                                                                                                                        Using and Exporting Blades

     –   HubProfile: a sketch defining the hub body will be (optionally) created. This sketch can be
         modified; however, you should take care to ensure that the sketch loop remains intact or the hub
         body will fail to regenerate.

         HubBody - (Optionally) the HubProfile sketch is revolved to create the HubBody feature in the
         tree view.
 •   BladeBody - The blade surface data is imported and lofted in DesignModeler to create the BladeBody
     feature in the tree view.
 •   StageFluidZone - (Optionally) the MasterProfile sketch is revolved and cut into a sector by the
     periodic surface to form the StageFluidZone body. This feature forms a sector of the fluid volume
     around a single blade, but the blade has not been removed from the volume.
 •   Enclosure - When the StageFluidZone is created, the blade (and any other connected geometry)
     is removed from the StageFluidZone body by the Enclosure feature.
 •   Named Selections - These are the labeled regions on the final Enclosure body: Blade, Hub, Shroud,
     Inflow, Outflow, PeriodicA and PeriodicB.

Loading and Modifying Blades from ANSYS BladeGen
If you create a blade from scratch in BladeEditor, or if you convert a BladeGen BGD file into BladeEditor

features (by clicking            ), then you can modify the blade by editing any of the features in the Tree
Outline. If you have imported the blade from BladeEditor, the blade will be dependent on the BladeGen
BGD file, but you can still modify the HubProfile sketch that appears under the associated MerPlane
feature.

     Note

     If you edit the hub sketch, make sure to maintain a closed edge loop when modifying this sketch
     or the hub body will fail to be generated. You can check the loop while editing the sketch by
     right-clicking in the viewer, choosing Select Loop/Chain and then selecting an edge of the loop.
     This will highlight the loop and let you inspect it in order to make sure that it is uniquely closed.

You can modify the blade geometry using any of the standard DesignModeler geometry features. Some
examples of the latter are:

 •   Adding edge blends to the blade geometry
 •   Trimming the blade and/or hub bodies
 •   Adding extrusions

Using and Exporting Blades
Once the model is ready in DesignModeler, you can quickly analyze it in the Mechanical application.
BladeEditor can also construct a solid model of the periodic flow passage that can be used to perform a
CFD analysis of the flow path geometry.

When needed, you can use DesignModeler to export the blade model to the Parasolid, IGES, or STEP file
format to bring it into your native CAD system.

You can also use BladeEditor to export the blade model for use in ANSYS TurboGrid or Vista TF.


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ANSYS BladeEditor

The following topics are discussed:
 Export to Vista TF (.geo)
 Export as Meanline Data (.rtzt file)
 Export to ANSYS TurboGrid

Export to Vista TF (.geo)
Similar to the ExportPoints feature, the VistaTFExport feature is used to define the parameters necessary to
write the flow path geometry data (.geo file) for Vista TF. The .geo file contains a 2D mesh of the flow path
geometry, including the locations of the blade leading and trailing edges. The .geo data also includes the
blade type, blade camber surface data, blade thickness data and blade count for each blade row.

If the ThroatArea feature (see Throat Area Feature (p. 39)) is used for a selected Blade, the throat information
for that blade will be written to the .geo file. This information may improve the calculation of the choke
mass flow rate in the Vista TF solver. Without this information, Vista TF will make its own estimate of the
throat area.

The feature properties are listed below.

Table 4 Details View for Meanline Export
Details of [Feature Name]
Export Points               [Feature Name]
Blade(s)                    [Blade feature selection]
Export to file              [Yes | No]
(If Export to file =        [.geo filename]
Yes)

Geo File Name
Streamwise Mesh             [Integer Value > 2]
Count
Spanwise Mesh               [Integer Value > 1]
Count
Selected Blades: [number]a
Blade 1                     [Blade reference]
Blade 2                     [Blade reference]
Blade 3                     [Blade reference]
a
Blade items are listed for all selected blades.


      Note

      The Vista TF solver expects the flow path (from inlet to outlet) to be oriented in the direction of
      the machine axis, which is the Z-axis.

The VistaTFExport feature requires you to select the Blade features that will be exported to the .geo file. The
selected blades must all belong to the same flow path. Therefore, the VistaTFExport feature can only export
the data for a single flow path. Only the selected blades in the flow path will be considered for export; all
other blades in the flow path will be ignored.


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46                                                      of ANSYS, Inc. and its subsidiaries and affiliates.
                                                                                                             Export as Meanline Data (.rtzt file)

The ‘Export to file’ option specifies whether to explicitly save the data to a .geo file. When using the ANSYS
Workbench project schematic, exporting to a file is unnecessary because the data is transferred automatically.
If the .geo file is explicitly written, then you need to specify the .geo file name.

The .geo file contains the geometry coordinates for the flow path in terms of quasi-orthogonal (q-o) ‘lines’
running from hub to shroud. The q-o lines are spaced approximately uniformly from inlet to outlet, based
on the mid-span meridional length. The number of q-o lines is specified by the ‘Streamwise Mesh Count’
property, where the minimum count is determined based on the number of selected blades in the flow
path. If the specified Streamwise Mesh Count is less than the calculated minimum, then the calculated
minimum will be used.

The number of q-o lines has a direct impact on the throughflow calculation accuracy and computation time.
Increasing the number can improve accuracy, but it will also increase computation time. Increasing the
number beyond a certain maximum may cause instabilities in the convergence process. Typical radial impellers
with an axial inducer should be calculated with around 15 q-o lines in the bladed region, which equates to
approximately a q-o line every 5° of curvature.

The Spanwise Mesh Count property specifies the number of points used to define each quasi-orthogonal
line; the points are uniformly spaced from hub to shroud. The minimum number is two. Increasing this
parameter will improve the exported geometry representation for highly curved blades, but it should not
be necessary to go beyond about 30. This parameter has no effect on the number of streamlines that are
actually used in the throughflow calculation.

When the .geo file is generated, a warning will be given for the VistaTFExport feature if the streamwise to
spanwise aspect ratio of any of the mesh elements is greater than 15 or less than 1/15. Depending on the
aspect ratio, you will be suggested to increase or decrease the appropriate streamwise or spanwise mesh
count.

Export as Meanline Data (.rtzt file)
To export meanline data, click the Add export points feature icon and set Export Type to Meanline.

The meanline data gives the camberline/thickness definitions on each output layer in an rtzt format (r, theta,
z, normal thickness.) Meanline data is exported based on the camber surface and thickness surface data
represented internally. Therefore, this data may not be representative of the blade if solid model operations
have been made to the blade geometry.

An ExportPoints (Meanline) feature defines the point output for exactly one blade row. A multi-blade row
model would require multiple ExportPoints features to output data for more than one blade row. All blades
(the main blade and all existing splitter blades) in a single blade row are exported by a single ExportPoints
feature. Regardless of whether you select a main blade or a splitter blade when defining the Blade parameter
of an ExportPoints feature, the Blade parameter will always display the main blade. If you suppress any blade
in a blade row, the ExportPoints feature for that blade row will also be suppressed.

The feature properties are listed below:

Table 5 Details View for Meanline Export
Details of [Feature Name]
Export Points        [Feature Name]
Export Type          [Meanline | TurboGrid]
Blade                [Blade feature selection]


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                                                 of ANSYS, Inc. and its subsidiaries and affiliates.                                          47
ANSYS BladeEditor

Point Distribution          [Uniform in M | Uniform in camber-
                            line length]
Number of Points            [Value>1]
                     a
Output Layers:
Output Layer 1?             [Yes | No]
Output Layer 2?             [Yes | No]
Output Layer 3?             [Yes | No]
a
Layer items are listed for all layers defined in the Flow Path.

For the Meanline export type, all blades in the selected blade row are exported. The ‘Number of Points’
property specifies how many points are exported from the leading edge to the trailing edge for each blade.
The number of points upstream and downstream of the blade(s) is determined by the length tolerance and
the shape of the flow path contours.

The Blade selection lets you select the Blade feature of interest. However, all blades in a blade row are ex-
ported.

Export to ANSYS TurboGrid
To transfer blade geometry data to the Turbo Mesh cell of a TurboGrid system, you need to link the Geometry
cell to the Turbo Mesh cell and create an ExportPoints feature in BladeEditor to specify which blade geometry
should be exported. The ANSYS TurboGrid export type provides the blade profile data in a format suitable
for defining the blade geometry in ANSYS TurboGrid.


To create the ExportPoints feature, click the               icon and set Export Type to TurboGrid. You
must then select the Blade feature or FlowPath feature and select the surfaces of the blade from which to
extract the blade profile data. The blade profile (point) data is automatically extracted from the blade solid
model at the specified output layers.

      Note

      Care must be taken to ensure that sufficient output layers are used when exporting so that the
      ANSYS TurboGrid blade surface is a reasonable approximation of the BladeEditor solid model.
      Note that using many output layers with a small point tolerance can cause Bspline surface lofting
      problems in ANSYS TurboGrid. In these cases, you may need to override the Blade Geometric
      Representation in ANSYS TurboGrid and change the Curve and Surface Types to 'Piece-wise linear'
      and 'Ruled', respectively.

You will need to use one ExportPoints feature for each blade that you wish to export, even if they are in
the same blade row. For example, if you have a main blade and a splitter, you will need to create two Ex-
portPoints features and select the appropriate blade surfaces for each feature.

You specify which exported blade(s) to load into ANSYS TurboGrid by editing the Turbo Mesh cell properties.
See Table 1: TurboGrid Turbo Mesh Cell Properties (p. 53) for more information.

Because the blade profile data is extracted from the blade surfaces, this feature can also be used to extract
blade profile data from an imported CAD model. The only requirement is that a FlowPath feature must be
defined to specify the output layers. If you specify a FlowPath as the Base Feature property, you will need
to specify the number of blades and the blade row number. The blade row number lets TurboGrid know


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48                                                      of ANSYS, Inc. and its subsidiaries and affiliates.
                                                                                                                              Export to ANSYS TurboGrid

how the exported blades are ordered, and whether any exported blades are part of the same blade row.
The blade rows are sorted in ascending order from inlet to outlet.

The blade profile data can also be exported to a file for use by an external application by setting the 'Export
to file' property to 'Yes'.

The feature properties are listed below:

Table 6 Details View for Export to ANSYS TurboGrid
Details of [Feature Name]
Export Points               [Feature Name]
Export Type                 [Meanline | TurboGrid]
Export to file              [Yes | No]
(If Export to file =        [Folder name]
Yes)

File Folder
(If Export to file =        [Filename prefix]
Yes)

File Prefix
Base Feature                [FlowPath or Blade feature selec-
                            tion]
Flow Path                   [FlowPath feature selection]
Blade Surfaces              [Named Selection for blade sur-
                            faces]
Blade Info from             [Blade feature | User Specified]
(if User Specified)         [Value>1]

Number of Blades
(if User Specified)         [Int Value]

Blade Row Num-
ber
Hub/Shroud Offset [0<Value<100]
%
Point Tolerance             [Value>1]
                     a
Output Layers:
Output Layer 1?             [Yes | No]
Output Layer 2?             [Yes | No]
Output Layer 3?             [Yes | No]
a
Layer items are listed for all layers defined in the Flow Path.




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                                                        of ANSYS, Inc. and its subsidiaries and affiliates.                                         49
ANSYS BladeEditor


Configuring the BladeModeler License
BladeModeler requires an ANSYS license to use, although BladeGen will run in "demonstration" mode without
the license (no saving or exporting is possible in this mode). Without the license the BladeGen system does
not appear in the Toolbox, and the only way to access BladeGen is to open a previously saved project that
contains a BladeGen system. Please contact your ANSYS representative to obtain a license for BladeModeler
if you do not already have one.

One BladeModeler license will permit a single user to have BladeGen, DesignModeler, and BladeEditor running
together in the same ANSYS Workbench session. This license sharing ability means that no additional
DesignModeler license will be required to use the full functionality of BladeModeler.

In order to use BladeEditor, you must set the Geometry license preference to ANSYS BladeModeler as follows:

 1.   In the ANSYS Workbench menu, select Tools > License Preferences.
 2.   In the License Preferences dialog box, click the Geometry tab.
 3.   If ANSYS BladeModeler is not the first license listed, then select it and click Move up as required to
      move it to the top of the list. Furthermore, you should select ANSYS DesignModeler in the list and
      set its value to 0 (which means “Don't Use”). This prevents DesignModeler from using an ANSYS
      DesignModeler license when an ANSYS BladeModeler license is not available.

      If ANSYS BladeModeler is not in the list then you need to obtain an ANSYS BladeModeler license.
 4.   Click OK to close the dialog box.

Click the Help button in the License Preferences dialog box for more information.




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50                                               of ANSYS, Inc. and its subsidiaries and affiliates.
                                                                                                 Configuring the BladeModeler License


Note

IMPORTANT WARNING FOR USERS THAT HAVE AN ANSYS DESIGNMODELER LICENSE

A BladeEditor model will be destroyed if it is modified by DesignModeler under the ANSYS
DesignModeler license. If your project involves a BladeEditor model, then you must ensure that
DesignModeler operates under the ANSYS BladeModeler license (in which case DesignModeler
is considered to be running as BladeEditor). Instructions for setting the license preferences appro-
priately are given above.

With DesignModeler running under the ANSYS DesignModeler license, it is very important that
you do not trigger the processing of any Geometry cell that represents a BladeEditor model; in
this case, processing the Geometry cell would cause the associated geometry file to be overwritten
with a corrupt version. Such processing can occur by updating all or part of the project, or by
editing the Geometry cell then making changes in DesignModeler then closing DesignModeler.

If you do edit a Geometry cell that contains a BladeEditor model, and you are using DesignModeler
under the ANSYS DesignModeler license, then DesignModeler will display question marks beside
some of the features listed in the tree view; these are the features that are not recognized by
DesignModeler because they are intended for BladeEditor. In this case avoid saving from
DesignModeler, then:

 1.    Either exit ANSYS Workbench or click File > New to start a new project.
 2.    Do not save the project when you are presented with a dialog box.
 3.    Configure your license preferences as specified above.
 4.    Reopen the project. The old (uncorrupted) files will be restored.




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                                             of ANSYS, Inc. and its subsidiaries and affiliates.                                  51
     Release 12.0 - © 2009 SAS IP, Inc. All rights reserved. - Contains proprietary and confidential information
52                               of ANSYS, Inc. and its subsidiaries and affiliates.
ANSYS TurboGrid
ANSYS TurboGrid is a meshing tool that is specialized for CFD analyses of turbomachinery bladerows. The
ANSYS TurboGrid documentation is available from the Help menu in ANSYS TurboGrid.

The main documentation is available from the Help menu in ANSYS TurboGrid, and consists of the following
parts:

 •   ANSYS TurboGrid Introduction
 •   ANSYS TurboGrid Tutorials
 •   ANSYS TurboGrid User's Guide
 •   ANSYS TurboGrid Reference Guide

To launch ANSYS TurboGrid from ANSYS Workbench, add the TurboGrid component system to your project
schematic, then edit the Turbo Mesh cell of that system.

The geometry can be loaded from the File menu in ANSYS TurboGrid, or it can be specified by linking a
Geometry or Blade Design cell upstream of the Turbo Mesh cell.

In the case when data is transferred to a Turbo Mesh cell from a Geometry cell, the Turbo Mesh cell has
properties that control this transfer. These are described in Table 1: TurboGrid Turbo Mesh Cell Properties (p. 53).
Before attempting to modify these properties, be sure to refresh the Turbo Mesh cell if it is in a Refresh Re-
quired state. Refreshing this cell causes the properties to be updated.

Table 1 TurboGrid Turbo Mesh Cell Properties
Group                 Name                               Description
Geometry Selec-       Flowpath Options                   This property displays a list of the
tion                                                     available flow paths and bladerows. Use
                                                         this information as a guide when specify-
                                                         ing the Flowpath and Bladerow proper-
                                                         ties (described below). Use the Refresh
                                                         command in the context menu to up-
                                                         date the list after linking.
                      Flowpath                           This property specifies which Flowpath
                                                         feature in BladeEditor contains the
                                                         bladerow that is to be loaded in ANSYS
                                                         TurboGrid.
                      Bladerow Number                    This property specifies which bladerow
                                                         (within the specified Flowpath feature)
                                                         is to be loaded in ANSYS TurboGrid.
                      Inlet Position                     This property specifies how the inlet
                      Method                             points are positioned in TurboGrid. The
                                                         Manual option means the user will spe-
                                                         cify these in TurboGrid. The Adjacent


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                                                  of ANSYS, Inc. and its subsidiaries and affiliates.                               53
ANSYS TurboGrid

Group                 Name                               Description
                                                         Blade option means the inlet points will
                                                         be calculated using the upstream
                                                         bladerow, specified below. Only avail-
                                                         able when multiple bladerows have
                                                         been specified in BladeEditor.
                      Upstream                           This property specifies the bladerow
                      Bladerow Number                    number for the bladerow that is imme-
                                                         diately upstream of the current
                                                         bladerow.

                                                         This property is available only when In-
                                                         let Position Method is set to Adjacent
                                                         Blade.
                      Outlet Position                    This property specifies how the outlet
                      Method                             points are positioned in TurboGrid. The
                                                         Manual option means the user will spe-
                                                         cify these in TurboGrid. The Adjacent
                                                         Blade option means the outlet points
                                                         will be calculated using the downstream
                                                         bladerow, specified below. Only avail-
                                                         able when multiple bladerows have
                                                         been specified in BladeEditor.
                      Downstream                         This property specifies the bladerow
                      Bladerow Number                    number for the bladerow that is imme-
                                                         diately downstream of the current
                                                         bladerow.

                                                         This property is available only when the
                                                         Outlet Position Method is set to Adja-
                                                         cent Blade.

Each ExportPoints feature in BladeEditor defines a single blade, is associated with a FlowPath, and has a
Bladerow Number. To model a series of consecutive bladerows in a turbomachine, you should define a series
of ExportPoints features associated with the same FlowPath feature, with Bladerow Numbers in numerical
order (lowest number at the inlet end of the machine). By using the same FlowPath number:

 •   You have access to the Turbo Mesh cell properties that collectively control the position of the inlet and
     outlet ends of each bladerow: Inlet Position Method, Upstream Bladerow Number, Outlet Position
     Method, Downstream Bladerow Number.
 •   The machine is eligible to be analyzed by Vista TF. For help on Vista TF, see Vista TF User's Guide (p. 61).

If you want a given bladerow to contain more than one blade geometry (for example, main blades with
splitter blades), create one ExportPoints feature for each unique blade in the bladerow, with each ExportPoints
feature based on the same FlowPath and given the same Bladerow Number. When more than one ExportPoints
feature matches the FlowPath and Bladerow Number criteria set in the Turbo Mesh cell properties, ANSYS
TurboGrid will create a bladerow with splitter blades.

You can access a context menu for the Turbo Mesh cell in the TurboGrid component system by right-clicking
the cell. Most of the commands that are available are standard, and are described in Systems and Cells. The



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                                                                                                                                  ANSYS TurboGrid

only context menu command that is specific to the Turbo Mesh cell is the Edit command, which opens ANSYS
TurboGrid.




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56                               of ANSYS, Inc. and its subsidiaries and affiliates.
ANSYS CFX-Pre
ANSYS CFX-Pre is a general-purpose CFD preprocessor that has a turbomachinery setup wizard for facilitating
the setup of turbomachinery CFD simulations. The ANSYS CFX-Pre documentation is available from the Help
menu in CFX-Pre.

                                                      .
The documentation is named “ANSYS CFX-Pre User's Guide”




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58                               of ANSYS, Inc. and its subsidiaries and affiliates.
ANSYS CFD-Post
ANSYS CFD-Post is a general-purpose CFD postprocessor that has features for facilitating the post-processing
of turbomachinery CFD simulations. The ANSYS CFD-Post documentation is available from the Help menu
in CFD-Post.

                                                       .
The documentation is named “ANSYS CFD-Post User's Guide”




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60                               of ANSYS, Inc. and its subsidiaries and affiliates.
Vista TF
The Vista TF program is a streamline curvature throughflow program for the analysis of any type of turboma-
chine, but has been developed in the first instance primarily as a tool for radial turbomachinery analysis.
The program enables you to rapidly evaluate radial blade rows (pumps, compressors and turbines) at the
early stages of the design.

Vista TF is provided by PCA Engineers Limited, Lincoln, England.

The documentation for Vista TF is provided in the following sections:
 Vista TF User's Guide
 Vista TF Reference Guide

Vista TF User's Guide
The Vista TF program is a streamline curvature throughflow program for the analysis of any type of turboma-
chine, but has been developed in the first instance primarily as a tool for radial turbomachinery analysis.
The program enables you to rapidly evaluate radial blade rows (pumps, compressors and turbines) at the
early stages of the design.

Vista TF is operated from ANSYS Workbench by working with the Vista TF component system. The latter is
comprised of three cells: a Setup cell, a Solution cell, and a Results cell:




The name of the Vista TF system is changeable upon first adding the system, or by right-clicking the blue
cell and selecting Rename, then typing in a new name. Note that the name of the system appears below
the system.

Vista TF uses the following input to define a run:

 •   A geometry (*.geo) file
 •   Setup cell properties
 •   Three Vista TF template files
     –   a control data file (*.cont)
     –   an aerodynamic data file (*.aert)
     –   a correlations data file (*.cort)

The general procedure for running a simulation in Vista TF is:

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Vista TF

 1.    Drag the Vista TF component system from the Toolbox to the Project Schematic, or double-click the
       system in the Toolbox.
 2.    Specify a geometry file using either one of the following methods:

       •   Connect an upstream Geometry cell that contains a VistaTFExport feature to the Setup cell.

           If there is more than one VistaTFExport feature, then the first valid and unsuppressed one is used.
       •   Right-click the Setup cell, select Import Geometry, and browse to select a geometry (*.geo) file.

 3.    Double-click the Setup cell, then configure the Setup cell properties.

       For details, see Vista TF Setup Cell Properties (p. 62).
 4.    Optionally customize one or more of the three template files (*.cont, *.aert, *.cort).

       For details on customizing the template files, see Customizing the Vista TF Template Files (p. 66).
 5.    Update the Solution cell, or update the Project, to generate a solution.
 6.    Double-click the Solution cell to view the solver output.
 7.    Double-click the Results cell to view the results in CFD-Post.

       The Results cell has one property that you can edit to control report generation.

The following topics are discussed:
 Vista TF Setup Cell Properties
 Customizing the Vista TF Template Files
 Vista TF Context Menu Commands

Vista TF Setup Cell Properties
The main properties that control Vista TF are associated with the Setup cell. To see the properties, do any
one of the following:

 •    Right-click the Setup cell and select Edit.
 •    Double-click the Setup cell.
 •    Right-click the Setup cell and select Properties.

A sample of the cell properties is shown in Figure : Properties of the Vista TF Setup Cell (p. 63).




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                                                                                                                      Vista TF Setup Cell Properties

Figure: Properties of the Vista TF Setup Cell




Table 1: Vista TF Setup Cell Properties (p. 63) describes each of the cell properties.

Table 1 Vista TF Setup Cell Properties
Group                  Name                               Description
General                Cell ID                            The name of the cell with which the
                                                          present set of properties is associated.
                       Machine Type                       This property appears when there is no
                                                          cell upstream of the Setup cell.

                                                          This property defines the machine type.

                                                          The choices are:

                                                          •    Pump

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Vista TF

Group              Name                               Description
                                                      •    Axial Compressor
                                                      •    Centrifugal Compressor
                                                      •    Fan
                                                      •    Axial Turbine
                                                      •    Radial Turbine
                                                      •    Hydraulic Turbine
                                                      •    Other
                                                      •    Unknown

                                                      This property specifies which template
                                                      files are used and which report is used
                                                      for the results. You can customize these
                                                      templates. For details, see Customizing
                                                      the Vista TF Template Files (p. 66).
                   Number of Blade                    This property appears when there is no
                   Rows                               cell upstream of the Setup cell.

                                                      This property defines the number of
                                                      blade rows in the geometry (.geo) file.
Solver Settings    Number of                          This property defines the number of
                   Streamlines                        meridional streamlines to use in the
                                                      calculation. For details, see Specification
                                                      of the Control Data File (*.con) (p. 74).
                   Maximum Itera-                     This property defines the maximum
                   tions                              number of solver iterations. For details,
                                                      see Specification of the Control Data File
                                                      (*.con) (p. 74).
Operating Condi-   Machine Rotation-                  This property defines the direction of
tions              al Direction                       rotation of the blades about the Z axis.

                                                      The choices are:

                                                      •    Right-handed
                                                      •    Left-handed

                   Machine Rotation-                  This property defines the rotational
                   al Speed                           speed of the machine.
                   Flow Option                        This property specifies the types of
                                                      boundary conditions.

                                                      The choices are:

                                                      •    Mass Flow
                                                      •    Pressure Ratio
                                                      •    Pressure Difference



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                                                                                                                  Vista TF Setup Cell Properties

Group              Name                               Description
                                                      For details, see Specification of the Con-
                                                      trol Data File (*.con) (p. 74) and Specific-
                                                      ation of Aerodynamic Data File
                                                      (*.aer) (p. 91).
                   Pressure Ratio                     This property defines the outlet-to-inlet
                                                      ratio of absolute total pressures (each
                   (For Flow Option                   pressure measured in the stationary
                   = Pressure Ratio)                  frame).
                   Pressure Differ-                   This property defines the outlet-to-inlet
                   ence                               difference of total pressures (each pres-
                                                      sure measured in the stationary frame).
                   (For Flow Option
                   = Pressure Differ-
                   ence)
                   Mass Flow Rate                     This property defines the inlet mass flow
                                                      rate.
                   Inlet Total Pres-                  This property defines the inlet absolute
                   sure                               total pressure (measured in the station-
                                                      ary frame).
                   Inlet Total Temper-                This property defines the inlet absolute
                   ature                              total temperature (measured in the sta-
                                                      tionary frame).
                   Inlet Swirl Angle                  This property defines the angle of the
                                                      inlet velocity measured with respect to
                                                      the meridional plane. A positive angle
                                                      implies that the flow swirls in the Ma-
                                                      chine Rotational Direction.
Reference Values   Reference Diamet-                  This property defines the reference dia-
                   er                                 meter for all blade rows. For details, see
                                                      Specification of Aerodynamic Data File
                                                      (*.aer) (p. 91).
                   Polytropic Effi-                   This property defines the small-scale
                   ciency                             polytropic efficiency for the machine.
Fluid Properties   Fluid Option                       This property defines the type of fluid
                                                      that flows through the machine.

                                                      The choices for this property are:

                                                      •    Ideal Gas
                                                      •    Liquid

                   Gas Specific Heat                  This property defines the specific heat
                   Cp                                 capacity (at constant pressure) of the
                                                      ideal gas.
                   (For Fluid Option
                   = Ideal Gas)
                   Specific Heat Ratio This property defines the specific heat
                                       ratio of the ideal gas.

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Vista TF

Group                Name                               Description
                     (For Fluid Option
                     = Ideal Gas)
                     Fluid Density                      This property defines the density of the
                                                        liquid.
                     (For Fluid Option
                     = Liquid)
                     Fluid Specific Heat                This property defines the specific heat
                                                        capacity of the liquid.
                     (For Fluid Option
                     = Liquid)
                     Dynamic Viscosity                  This property indicates the dynamic
                                                        viscosity of the fluid as follows:

                                                        •    A value less than 1 [N s m^-2] (or
                                                             equivalent value in other units) is
                                                             interpreted as the dynamic viscosity.
                                                             Note that the value must be greater
                                                             than 0.0000001 [N s m^-2].
                                                        •    A value of 0 causes Vista TF to calcu-
                                                             late the dynamic viscosity from an
                                                             inbuilt equation for dynamic viscos-
                                                             ity based on Sutherland’s law and
                                                             the Inlet Total Temperature. This
                                                             works only for an ideal gas.
                                                        •    A value greater than 1 [N s m^-2]
                                                             (or equivalent value in other units)
                                                             is interpreted as the Reynolds num-
                                                             ber, in which case Vista TF calculates
                                                             the dynamic viscosity using this
                                                             Reynolds number, the Reference
                                                             Diameter, the Machine Rotational
                                                             Speed, and the fluid density.

Initial Conditions   Initial Cm/U_ref                   This property serves as an initial guess
                                                        for the meridional velocity divided by a
                                                        characteristic velocity, where the latter
                                                        is half the Reference Diameter multi-
                                                        plied by the Machine Rotational Speed.
                                                        For more information, see the descrip-
                                                        tion for cm_start in Specification of
                                                        the Control Data File (*.con) (p. 74).

Customizing the Vista TF Template Files
When you run Vista TF, one of each of the *.cont, *.aert, and *.cort data files are copied from the Vista TF
template directory into your working directory as required (that is, if they are not already present in the
working directory). The exact *.cont, *.aert, and *.cort files that are copied (and then used during a run) depend
on the Machine Type setting in the Setup cell properties. You can use custom versions of any of the *.cont,
*.aert, and *.cort files. To customize one of these files:


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                                                                                                              Vista TF Context Menu Commands

 1.    Import the template you want to customize by right-clicking the Setup cell and selecting one of the
       Import Template commands.

       The selected template file is copied to the working directory. If you import the same template file
       more than once, the name of the copied file is changed automatically to produce a unique file name;
       the last one imported will take effect when you start a run.
 2.    From the Workbench main menu, select View > Files to see the template files you have imported.
 3.    Right-click the template file that you want to customize, and select Open Containing Folder.
 4.    Open the template file in a text editor and change it.

       In these files, do not change setting values that are between a pair of braces (“{” and “}”). You can
       change setting values which are not wrapped in braces.

       The settings of the template files correspond with the settings of the *.con, *.aer, and *.cor files which
       are described in Specification of the Control Data File (*.con) (p. 74), Specification of Aerodynamic Data
       File (*.aer) (p. 91), and Specification of Correlations Data File (*.cor) (p. 101).

Vista TF Context Menu Commands
You can access a context menu for each cell in the Vista TF component system by right-clicking a cell in the
system. Most of the commands that are available are standard, and are described in Systems and Cells. The
context menu commands that are specific to the Vista TF system cells are described in Table 2: Context Menu
Commands Specific to the Vista TF System Cells (p. 67).

Table 2 Context Menu Commands Specific to the Vista TF System Cells
Cell                   Command                                            Description
Setup                  Edit                                               This command opens the Vista
                                                                          TF properties view.
                       Import Geometry                                    This command enables you to
                                                                          specify the geometry file,
                                                                          provided that there is no up-
                                                                          stream Geometry cell linked
                                                                          to the Setup cell.
                       Import Template                                    This command enables you to
                                                                          import a template file. For de-
                                                                          tails, see Customizing the Vista
                                                                          TF Template Files (p. 66).
Solution               View Solver Output                                 This command opens the Vista
                                                                          TF screen output (.scn file) for
                                                                          viewing. For details, see Screen
                                                                          Output Files
                                                                          (screen.scn) (p. 74).
                       Continue Calculation                               This command restarts the
                                                                          solver. You can use this com-
                                                                          mand to continue a run that
                                                                          did not converge; in this case,
                                                                          the Update command may not
                                                                          work because the cell is
                                                                          already up-to-date.


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Vista TF

Cell                    Command                                            Description
Results                 Edit                                               This command opens the res-
                                                                           ults in CFD-Post.

Vista TF Reference Guide
The Vista TF program is a streamline curvature throughflow program for the analysis of any type of turboma-
chine, but has been developed in the first instance primarily as a tool for radial turbomachinery analysis.
The program enables you to rapidly evaluate radial blade rows (pumps, compressors and turbines) at the
early stages of the design.

The key aspect of this document is the input and output data specification for the program and how to run
it.

The input files include a control file, an aerodynamics file, a geometry file, a correlations file, and can also
include a restart file providing data from a previous converged simulation. The input files include comment
lines to help the reader to identify the parameters.

The output files include a results file with text output for analysis of the simulation giving:

 •     Data on streamlines and quasi-othogonals (short for “quasi-orthogonal calculating stations”)
 •     Various files with the same information that can be used for plotting the results
 •     A file which monitors the history of the simulation
 •     A file to act as interface to other software systems
 •     A restart file which can be used to initialise a further simulation.

For radial pump and turbomachinery calculations in subsonic flow the program is very robust, but some
tips on possible problems with running the program are also provided.

The topics in this guide are:
 Running Vista TF from the Command Line
 Input and Output Data Files for Vista TF
 Software Limitations
 Streamline Curvature Throughflow Theory
 Appendices

Running Vista TF from the Command Line
You can run Vista TF from the command line of your operating system. By default, the executable will look
in the current directory for the required input files for your case. One of the input files, which has a default
name of vista_tf.fil, contains the names of the other input files that are to be used for the case. If
this input file has a different name, specify that name as the first command line argument. For example:

VistaTF.exe myfile.fil

When the executable runs, it writes text output messages to the console. To redirect these messages to a
file, append -silent to the command line. The default file name for storing the redirected output messages
is screen.scn. To store the output messages in a file of a different name, specify that name following
-silent.




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                                                                                                     Input and Output Data Files for Vista TF

After running the program, several files are produced in .csv format as the basis for producing plots with
CFD-Post or in .txt format as the basis for producing plots with Tecplot.

The input and output files for VistaTF.exe are described in detail in Input and Output Data Files for Vista
TF (p. 69).

Input and Output Data Files for Vista TF
The following sections describe the input and output files for VistaTF.exe.
 The Auxiliary File with the Default Name: vista_tf.fil
 Overview of Input Files
 Overview of Output Files
 Specification of the Control Data File (*.con)
 Specification of the Geometry Data File (*.geo)
 Specification of Aerodynamic Data File (*.aer)
 Specification of Correlations Data File (*.cor)
 Specification of the Output Data File (*.out)
 Specification of the Text Data Files (*.txt)
 Specification of the CFD-Post Output Files (*.csv)
 Specification of Convergence History Data File (*.hst)

The Auxiliary File with the Default Name: vista_tf.fil
You specify the input data and output data file names in an auxiliary data file which has the default filename
vista_tf.fil. This file can have another name if this name is passed to the program through a command-
line argument to specify the auxiliary filename, as described in Running Vista TF from the Command Line (p. 68).
If no command-line argument is specified in this way, then the program assumes that the file has the name
vista_tf.fil. This auxiliary file in turn must contain the necessary filenames for the input and output
files in the following order and form:

 control datafile name                       prefix.con
 geometry datafile name                      prefix.geo
 aerodynamic datafile name                   prefix.aer
 correlation datafile name                   prefix.cor
 results output file name                    prefix.out
 convergence history filename                prefix.hst
 text data output file name                  prefix.txt
 Cfx-post output file name                   prefix.csv
 restart datafile name                       prefix.rst
 Interface output file                       prefix.int

Note that the prefixes need not be identical for a given run. In fact this is not usually the case. An example
of a vista_tf.fil file is:
 standard_control.con
 impeller_XYZa.geo
 design_point.aer
 radial_impeller.cor
 results.out
 history.hst
 impeller.txt
 cfx_post.csv
 restart.rst
 stream.int

Note that the program also produces and uses other files in special situations as outlined below; their names
do not need to be specified separately because they are determined by the program. The data files, results
files, and the file vista_tf.fil should be in the same directory. If the history (.hst) file already exists


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Vista TF

in the working directory before the program is run, it will be overwritten. If the restart (.rst) file already
exists in the working directory before the program is run, it will be overwritten only if the solution has
converged or reached the maximum number of iterations that you have specified. If the output (.out) file
and the plot files (.txt, and .csv) already exist in the working directory before the program is run, they
will be overwritten. The program will not prompt you for permission to overwrite these files.

Overview of Input Files
Four input data files are always needed:
 Control data file (.con)
 Geometrical data file (.geo)
 Aerodynamic data file (.aer)
 Correlations data file (.cor)

A fifth input file will be used if it is available and if you specify that it should be used:
 Restart data file (.rst)

The division of the input data into separate files provides a simple and clear way to vary or retain the annulus
geometry, the aerodynamic conditions, the blade element data, or the correlations being used, without
changing all the files in use. Typically during the design process, you will change the .geo file to examine
a new geometry, and the .aer file to examine new operating points or boundary conditions, and you will
leave the .con and .cor files untouched once you have configured their settings to meet the requirements.

The data specified in the individual files is structured to be as logical as possible, but some small overlap
between the different files is inevitably necessary. The structure may appear more complicated than necessary,
but this arises from the requirement that ultimately the program should calculate all types of turbomachinery
in single stage and multistage configurations, both as ductflow and as throughflow calculations. During the
development an attempt has been made to include a built-in “expert system” in the program. For example,
the program itself is able to identify whether a particular blade row is a radial compressor impeller or a ra-
dial turbine inlet guide vane (from the geometry) and ultimately will be able to select automatically the
most appropriate correlations to be used. In general many parameters may be set to zero and the program
selects the value it deems appropriate. “Expert parameters” allow you to override the selections that the
program would automatically make.

The functions of the five input data files are summarized next:

Control Data File (.con)
This is a short file giving values of identifiers of the file (title and headers) and control information and
constants defining such choices as the number of streamline calculating planes, the convergence tolerance,
the relaxation factors, and so on. Various “expert” parameters are also specified in this file. Also specified in
this file are the planes and stations for which output information is required, and the level of detail requested
on these planes.

To make the program easier to use, you can specify many of these parameters as 0.0, 1.0, or 0, and the
program will then make a sensible choice of the value for the parameter concerned, so that typically you
are only concerned with two or three parameters in this file. The control parameters that determine the se-
lection of particular numerical models are also defined in this file, for example the type of span-wise mixing
or the model for blade row choking. In general, this input file does not need to be changed from run to run.

Geometry Data File (.geo)
The geometry data file contains the dimensions of the annulus in terms of the axial and radial coordinates
of the quasi-orthogonal calculating planes at hub and casing, and information to identify the type of calcu-

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                                                                                                                                   Restart Data File (.rst)

lating station (such as duct, stator, or rotor). Calculating planes can represent regions of a duct or blades
(leading edges, trailing edges, and internal stations) and can be curved or linear. For linear calculating planes
(which, by definition, are straight in the meridional plane), details of the geometry of each calculating plane
are specified at only two points and intermediate geometric values are interpolated linearly from these,
whereas curved planes require more points to be specified across the span. For curved duct calculating
planes, this geometry data specifies the co-ordinate points along the curved calculating plane. In blade regions,
the coordinates of the calculating plane, together with information about the blade geometry at this location,
must be specified (including the number of blades, blade lean angles, and blade thickness). For each blade
row, additional geometrical parameters can be specified that might be relevant for the correlations (such
as the throat area, the location of the throat, the location of maximum camber, the maximum thickness, the
trailing edge thickness, and the tip clearance).

In general, the geometry data file will be generated automatically using a blade geometry definition program
(such as ANSYS BladeEditor, or Vista GEO of PCA). A geometry conversion program is available to convert
data from the BladeGen meanline RTZT output format into the .geo file format for the throughflow program
and this has been tested for radial impeller rotors and stators, and axial stator and rotor blade rows (com-
pressors and turbines); see Appendix G: The RTZTtoGEO Program (p. 147). Other custom tools are available for
conversion of geometrical data from specific formats into the Vista TF .geo file format, and others can be
prepared as required.

Aerodynamic Data File (.aer)
The aerodynamic data file contains the definition of the fluid, boundary conditions, and operating data such
as inlet conditions and rotational speed. It includes parameters related to aerodynamic models for the mean
stream surface description, and the spanwise mixing coefficient.

Correlation Data File (.cor)
The correlation data file provides details of control parameters and empirical constants and data for the
particular choice of empiricism that has been chosen. The method allows a general specification of losses,
flow angle, and blockage for all calculating planes and across the span through the definition of the spanwise
variation of these parameters at particular quasi-orthogonal locations and for particular blade rows. Ultimately,
in many cases, if default values of zero are chosen for these parameters then the program should automat-
ically select appropriate correlations and make its own choice of correlation parameters.

Restart Data File (.rst)
This restart file contains some key information from a previous calculation in a non-dimensional form. Note
that the restart file can be for different flow conditions and for a different geometry but it must have the
same number of quasi-orthogonal calculating stations and streamlines as the current calculation. If the restart
data file has been generated from a calculation with similar geometry and flow conditions as the current
calculation, it provides a much better initial estimate of the flow and the streamline positions than the first
estimate generated internally within the program, promoting more rapid convergence. A restart with un-
changed conditions and geometry will generally have a meridional velocity error of less than 2% and will
converge almost immediately, except for choked flows where more iterations are needed. Convergence with
the restart file is never immediate, even with unchanged geometry and flow conditions, because not all of
the solution is saved to the restart file, and so some data needs to be regenerated over a few iterations of
the solution. For small changes in flow conditions or geometry, the number of iterations when using the
restart file is generally less than 50% of that required when starting from the program's own first estimate.

An existing restart file cannot be used if the number of streamlines or quasi-orthogonals is changed. The
program recognizes if the number of streamlines or quasi-orthogonals has been changed and makes a new
cold start in this case.

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You do not have to be concerned with the content and format of the restart file because it is generated
automatically at the end of a run of the program, and is automatically used if it is available. No further in-
formation is provided here with regards to the content of the restart file. In some situations where it is difficult
to obtain convergence, the restart file can be used to store results for a converged operating point (at lower
speed, for example) and then the required operating condition can be obtained by starting from the restart
file with new flow conditions. In other cases where an un-converged solution has been stored in the restart
file, it is possible that using the restart file can be disadvantageous as a starting point for a new simulation,
and a cold-start may be better.

The restart file can also be used for reducing the number of computations when the program is coupled to
an optimizer. In this case, an additional restart file with the name best_restart.rst is used and generated.

Overview of Output Files
The program always creates the following three output files:

 •   Results output file (.out)
 •   Convergence history file (.hst)
 •   Restart data file (.rst)

In addition, the program can create the following output files of tabular data for plot and display purposes,
depending on the value of the parameter i_display in the control file:

 •   Several comma separated variable output files for CFD-Post (.csv)
 •   Several text output files in a format suitable for Tecplot (.txt)

There is one CFD-Post output file for a calculation with no blade rows and four additional files for each blade
row. There are two Tecplot output files for a calculation with no blade rows, and an additional file for each
blade row.

In addition, the program can create a data file containing data in a specific format for use with other programs:

 •   Interface output file (.int)

and a file which can be produced as an alternative to the screen output:

 •   Screen output file (screen.txt)

Results Output File (.out)
This contains rudimentary details of the data used for the calculation and the results of the calculation at
every plane and radial station for which output has been requested. An overview of the content of this file
is given in Specification of the Output Data File (*.out) (p. 111).

Convergence History File (.hst)
This contains a recording of the input data, followed by details of the convergence of the main iterative
procedures, and extensive details of the terms in the radial equilibrium equation for each stream tube and
calculating plane. It is rare for this to be examined in any depth, but this can be useful to identify problems
if the solution fails to converge.




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                                                                                                     Text Data Output Files for Tecplot (.txt)

Restart Data File (.rst)
This restart file stores information from a converged calculation in a non-dimensional form. It provides a
much better initial estimate of the flow and the streamline positions than the first estimate generated internally
within the program. It reduces the calculation time for a calculation with slightly modified geometry or
changed aerodynamic data by more than 25%. If an existing restart file is available, it will be overwritten by
the program.

Comma Separated Variable Output Files for CFD-Post (.csv)
Depending on the value of i_display in the control file, the following files are produced:

 •   prefix.csv
 •   global_prefix.csv

together with four additional files produced for each blade row from 1 to n:

 •   row_0n_hub_prefix.csv
 •   row_0n_mean_prefix.csv
 •   row_0n_tip_prefix.csv
 •   row_0n_loading_prefix.csv

The first file (prefix.csv) contains key results of the calculation at every calculating plane and streamline
in a form that can be used for setting up a meridional contour plot of the results. The second contains a
summary of the global performance and reference parameters for the calculation. The additional four .csv
files are produced for each blade row in the calculation. These contain the same information as in the row
data from the .txt files, but separated into hub, mean, and tip streamline data, which is information along
the blade calculating station from leading to trailing edge on the hub, mean, and tip streamlines. The addi-
tional file contains spanwise variation of data. This can be used to define typical blade loading diagrams
and incidence plots for each blade row.

Even if no .csv file is required, the prefix.csv file still needs to be specified in the vista_tf.fil
file.

Text Data Output Files for Tecplot (.txt)
Depending on the value of I_display in the control file, the following files are produced:

 •   prefix.txt
 •   test_prefix.txt

Together with one additional file produced for each blade row from 1 to n:

 •   row_0n_prefix.txt

The first file (prefix.txt) contains key results of the calculation at every calculating plane and streamline
in a form that can be used for setting up a meridional contour plot of the results, using Tecplot software.
This is an ASCII file which is formally correct for presenting the results in graphical form with the plot pro-
cessing software Tecplot, but can be used by other plot systems (such as Excel) with appropriate conversion
or macros. A standard layout file for Tecplot (flowfield_2d.lay) has been prepared for typical meridi-
onal plots from Vista TF calculations. There are no macros included in this so this may need some adjustment
for a typical case (scale of axes, level of contour values, and so on). The second text file (test_prefix.txt)


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contains the grid of the initial estimate of the streamlines and quasi-orthognals. This can be useful for de-
bugging purposes and can be used to plot the initial grid of an un-converged calculation to identify any
specific problems with this. The additional .txt files are produced for each blade row in the calculation
(row_0n_prefix.txt where n is the number of the blade row from the inlet). These can be used to
define typical blade loading diagrams and incidence plots for each blade row. The Layout files for Tecplot
that have been prepared in advance assume that the .txt file has the prefix “impeller”       .

Even if no .txt file is required, the prefix.txt file still must be specified in the vista_tf.fil file.

Interface Output Files (.int)
If you request the generation of an interface file for another analysis program then the appropriate files are
also generated. The first use of this has been established to allow a summary of the results to be obtained
as input to an optimizing software system. A second option will be to generate the .stream file for MISES
blade-to-blade calculations providing the streamtube thickness and the radius along a stream section. Even
if no interface file is required, the .int file still must be specified in the vista_tf.fil file.

Screen Output Files (screen.scn)
In normal operation, the progress of the program can be seen on the screen. If the command line includes
a parameter -silent, the screen results will be written to a separate file called screen.scn and not to
the screen. If this parameter is not present, this output goes to the screen. If a name follows this parameter,
the screen results are printed to a file with this name.

Specification of the Control Data File (*.con)
The control data file includes sections of text that help you to identify the parameters defined here. Note
that if values are set to 0.0 or 0 then standard values are used, so typically you do not have to worry about
this input. If zero values are specified for some parameters then the values actually selected by the program
are written to the output file. Standard forms of this file are available for editing to meet the specific require-
ments, whereby in most cases no modification of the file is necessary. An example of a control data file is
given in Appendix B: Example of a Control Data File (*.con) (p. 130).

Section 1: Character strings identifying the control data (max 72 characters/line)
   The syntax is:
     Character string - title(1)
     Character string - title(2)
     Character string - title(3)

Section 2: Integer control parameters
   The syntax is:
     n_sl    max_it_main        max_it_mass


     Parameter              Description
     n_sl                   Number of meridional streamlines

                            Notes:
                            •     Must be an odd number so that there is always a mid
                                  streamline.
                            •     Typically n = 9 or 17. If n_sl = 0, then 9 will be used.
                            •     Maximum n_sl = max_n_sl = 19.


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                                                                                                                Screen Output Files (screen.scn)

    Parameter              Description
                           •     If the mixing model is being used, (i_mix > 0 in section
                                 4) then there has to be a minimum of 9 streamlines.
    max_it_main            Maximum number of iterations of the main streamline
                           curvature loop in the iterative method.

                           Notes:
                           •     Typically specified as 500 but fewer are generally needed
                                 for simple radial compressor calculations to attain conver-
                                 gence.
                           •     If max_it_main < 4 then max_it_main = 4, so that
                                 at least 4 iterations are always done as a minimum.
                           •     If max_it_main = 0 then max_it_main = 500.
                           •     If the flow reaches the convergence limit before the
                                 maximum number of iterations is reached then the calcu-
                                 lation is automatically stopped earlier.
    max_it_mass            Maximum number of iterations for internal mass flow loop
                           at each quasi-orthogonal calculating station.

                           Notes:
                           •     Typically 10 and if max_it_mass = 0, then
                                 max_it_mass = 10.
                           •     If max_it_mass < 5 then max_it_mass = 5; experience
                                 shows that this is a sensible value.
                           •     If max_it_mass > 20 then max_it_mass = 20.
                           •     If the mass flow convergence tolerance at a particular
                                 quasi-orthogonal is reached before the maximum number
                                 of iterations are completed then mass flow iteration is
                                 stopped early.



Section 3: Integer control parameters that control input and output data
   The syntax is:
    i_print_plane    i_print_level                i_progress             i_display             i_restart            i_interface

   Note that setting all of these parameters to 0 gives a standard form of output.

    Parameter              Description
    i_print_plane          Determines the quasi-orthogonal calculating planes at which
                           data is output into the results file.

                           = 0, as i_print_plane = 4

                           = 1, output at no planes

                           = 2, data at inlet and outlet planes only



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     Parameter          Description
                        = 3, data at leading edges and trailing edges and inlet and
                        outlet planes only

                        = 4, data at all planes

                        Note:

                        The extent of the data printed at each plane is determined
                        by i_print_level.
     i_print_level      Determines the level of output data printed into the results
                        file at each output plane.

                        = 0, standard output (as iprint_level = 3)

                        = 1, very limited data at each plane

                        = 2, generous level of data at each plane

                        = 3, extensive data at each plane

                        Note:

                        The planes at which output is available are defined by the
                        parameter i_print_plane.
     i_progress         Determines the extent of intermediate data that is printed
                        to the various files.
                        •     If i_progress = 0 then no intermediate information is
                              printed.
                        •     If i_progress = 1 then intermediate progress of the
                              iterations are printed to the history file.
                        •     If i_progress = 2 then data is printed to the history
                              file and to the screen.
     i_display          Determines extent of tabular data output which is prepared
                        for displaying the results with other plot and post-processing
                        tools:

                        Notes:
                        •     If i_display = 1, then no plot files are produced.
                        •     If i_display = 0 then the output files of type .txt are
                              produced for display of the results with Tecplot.
                        •     If i_display = 2, then a comma separated variable file
                              with extension .csv is produced for display of the results
                              with CFD-Post.
                        •     If i_display = 3, then both i_display = 0 and 2
                              above are activated.
                        •     Other output formats can be incorporated as requested.
     i_restart          Determines whether the restart file should be used and
                        whether the results will overwrite the restart file contents.

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                                                                                                                Screen Output Files (screen.scn)

    Parameter              Description
                           Notes:
                           •     If i_restart = 0, the restart file (prefix.rst) will be
                                 used automatically if it is present (a warm start) and its
                                 content will be overwritten automatically at the end of a
                                 normal calculation. Note that this also overwrites the re-
                                 start file even if the iterations are not converged, so that
                                 a second start with the same number of iterations starts
                                 with a better approximation. This is the normal way to
                                 use the program. The restart file includes the number of
                                 quasi-orthogonals and streamlines. If i_restart = 0
                                 and this number has changed then the program makes
                                 a cold start with its own estimate of inititial conditions
                                 (as in i_restart = 1).
                           •     If i_restart = 1 the restart file (prefix.rst) will not
                                 be used even if it is available and the program will set up
                                 its own initial conditions (a cold start). The content of the
                                 restart file will be overwritten as under 1 above. This is
                                 not generally recommended but can be useful in debug-
                                 ging difficult cases. This is equivalent to deleting the ex-
                                 isting restart file and using option 1 above.
                           •     i_restart = 2 and 3 are special options for running
                                 the program when coupled to an automatic optimizer. In
                                 these cases the use of a good restart file reduces the
                                 number of iterations needed and brings a reduction in
                                 calculating time. Unfortunately some of the geometries
                                 being examined may be poor and so it is inadvisable to
                                 overwrite the restart file with poor results. If i_restart
                                 = 2 then the file runs with a restart file called best_re-
                                 start.rst and writes the results on to prefix.rst.
                                 If i_restart = 3 then the file runs with a restart file
                                 called best_restart.rst and also writes the results
                                 on to the same file best_restart.rst. In both cases
                                 if the restart file best_restart.rst is not present
                                 then the internal initial estimate is used (a cold start).
    i_interface            Determines the type of output interface file that is generated.

                           Notes:
                           •     If i_interface = 0 then no output interface file is
                                 generated.
                           •     If i_interface = 1 then the prefix.int file contains
                                 a summary of the results for use in radial compressor
                                 optimization.
                           •     Other options are in preparation, such as a link to the
                                 blade-to-blade program MISES.



Section 4: Integer control parameters for various models and reference parameters
   The syntax is:

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     i_expert    i_flow        i_fluid         i _inbc            i_mass          i_mix          i_ree


     Parameter             Description
     i_expert              Allows special calculations to be carried out making use of
                           development features of the program. Normally you would
                           set the value of this parameter to 0 or 1, but other expert
                           features of the program may be modified with this control
                           parameter. Each digit of the parameter has an influence on
                           its effect.

                           Notes:
                           •     The last digit controls the choke calculation mode. Using
                                 a value of zero for the last digit causes the choke mass
                                 flow limitation to be eliminated which may be more ro-
                                 bust in difficult cases. Calculations of new cases should
                                 start in this mode.
                           •     Using a value of 1 for the last digit, enables the choke
                                 mass flow limitation calculation. This requires exact data
                                 for the throat areas to be specified and should only be
                                 used if this is available. It is necessary to set this value to
                                 1 when using iteration to pressure ratio in choked stages.
                           •     The second-last digit controls the blending function cal-
                                 culation for the deviation between the blade angle and
                                 the flow angle as follows:

                                 0 - Turbines use departure angle at the leading and trail-
                                 ing edge ends, Compressors use swirl at the leading edge
                                 and departure angle at the trailing edge.

                                 1 - Turbines and compressors use the departure angle for
                                 the leading and trailing edges.

                                 2 - Turbines and compressors use departure angle at the
                                 trailing edge and relative swirl at the leading edge.

                                 3 - Turbines and compressors use departure angle at the
                                 trailing edge and the absolute swirl at the inlet.

                                 4 - Compressors use swirl at the leading edge and depar-
                                 ture angle at the trailing edge; turbines use swirl at the
                                 outlet and departure angle at the leading edge.

                                 5 - Compressors use swirl at the leading edge, departure
                                 angle at the trailing edge; turbines use swirl at the trailing
                                 edge and departure angle at the leading edge.
     i_flow                Determines the input definition for the reference flow para-
                           meters (which are input in .aer file).

                           Notes:
                           •     i_flow = 0 then ref_mach, ref_phi, and ref_d, are
                                 specified, but if ref_mach > 3 then it is interpreted as


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                                                                                                       Screen Output Files (screen.scn)

Parameter         Description
                        ref_u, so this is equivalent to ref_u, ref_phi, and
                        ref_d.
                  •     i_flow = 1 then ref_n, ref_mass, and ref_d are
                        specified.

                        Note: If there is more than one spool in the calculation
                        with different rotational speeds, then this is taken into
                        account as follows:

                        - If i_spool = 2 and i_flow = 1 then ref_n1,
                        ref_n2, ref_mass, and ref_d are specified.

                        - If i_spool = 3 and i_flow = 1 then ref_n1,
                        ref_n2, ref_n3, ref_mass, and ref_d are specified.
                  •     i_flow = 2 then ref_n, ref_volume, and ref_d are
                        specified.
                  •     i_flow = 3 then ref_u, ref_mass, and ref_d are
                        specified.
                  •     i_flow = 4 then ref_u, ref_volume, and ref_d are
                        specified
                  •     i_flow = 5 then ref_n, ref_mass, and ref_d are
                        specified together with the ref_pr (total to static pres-
                        sure ratio between inlet plane and the last trailing edge
                        on the mid-streamline). The value of ref_mass is a start
                        value for mass flow in the iteration to pressure ratio and
                        has no effect on the final solution.
                  •     i_flow = 6 then ref_n, ref_mass, and ref_d are
                        specified together with ref_pr (total to static pressure
                        ratio) together with n_p_te (the total number of trailing
                        edges at which a guessed value of the static pressure ratio
                        is specified, followed by the guessed pressure ratios at
                        each trailing edge, including the last, which is also defined
                        by ref_pr.
                  •     i_flow = 7 then ref_n, ref_mass, and ref_d are
                        specified together with the ref_p (static pressure at the
                        last trailing edge on the mid-streamline). The value of
                        ref_mass is a start value for mass flow in the iteration
                        to outlet pressure and has no effect on the final solution.
                        This option may be useful for low speed devices where
                        pressure ratio becomes indeterminate.
                  •     i_flow = 8 then ref_n, ref_mass, and ref_d are
                        specified together with the ref_p (static pressure at
                        trailing edge pane) together with n_p_te (the total
                        number of trailing edges at which a guessed value of the
                        static pressure is specified, followed by the guessed
                        pressures at each trailing edge, including the last, which
                        is also defined by ref_p.


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     Parameter         Description
                       •     i_flow = 9 then ref_n, ref_mass, and ref_d are
                             specified together with the ref_cu (absolute swirl velo-
                             city at the last trailing edge on the mid-streamline). The
                             value of ref_mass is a start value for mass flow in the
                             iteration to outlet swirl and has no effect on the final
                             solution. This option may be useful for turbine calculations
                             where the last blade row is a turbine rotor.
                       •     Other options are available for debugging purposes.
                       •     The geometry definition of Vista TF assumes clockwise
                             rotation. This leads to a certain convention for the sign
                             of the blade angles (see Appendix A: A Note on Sign Con-
                             vention for Angles and Velocities (p. 127)). In some cases
                             you may have a counterclockwise machine with blade
                             angles of the opposite sign. To avoid the need to change
                             all the angles specified in the .geo file, an option is
                             provided whereby the value of i_flow is given a negat-
                             ive sign.
     i_fluid           Determines the model for the equation of state of the fluid:
                       •     If i_fluid = 0 then ideal gas with constant specific heat.
                       •     If i_fluid = 1 then liquid.
     i_inbc            Determines the type of inlet boundary conditions:
                       •     i_inbc = 0 then input values are total pressure, total
                             temperature and swirl (r x cu, that is radius times circum-
                             ferential component of the absolute velocity) on the input
                             plane.
                       •     i_in_bc = 1 then input values are total pressure, total
                             temperature, and absolute flow angle.
     i_mass            Determines whether the mass flow is uniformly distributed
                       across streamlines or not.
                       •     i_mass = 0 then mass flow between each streamline is
                             the same.
     i_mix             Determines which mixing model is used:
                       •     i_mix = 0 then no mixing model.
                       •     i_mix = 1 then a spanwise mixing model based on eddy
                             diffusion across the streamlines will be used. Note that
                             this requires a minimum of 9 streamlines (n_sl => 9).
     i_ree             Determines the form of the radial equilibrium equation that
                       is used to determine the velocity gradient along the quasi-
                       orthogonal.
                       •     i_ree = 0 then the equations as given in the paper of
                             Casey and Roth (1984) are used, except that the dissipa-
                             tion term is set to zero and the blade force term is set to
                             zero at a trailing edge and at a leading edge.



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                                                                                                               Screen Output Files (screen.scn)

   Parameter              Description
                          •     i_ree = 1 then the solution is as for i_ree = 0 but the
                                dissipation term is not set to zero but the equations as
                                given in the theory documentation are used.
                          •     i_ree = 2 then the dissipation term is not set to zero
                                but the equations given in the paper of Casey and Roth
                                (1984) are used.
                          •     i_ree = 3 then the velocity gradient in the radial equi-
                                librium equation is reduced by the factor grad_ree
                                given in section 5. This is useful for debugging difficult
                                cases and the simulation becomes similar to a mean-line
                                calculation with no gradient of meridional velocity across
                                the span. If grad_ree = 1.0 then selecting i_ree = 3
                                has no effect.



Section 5: Convergence and damping factors
   The syntax is:
    damp_sc    damp_vl        cm_start          tolerance_cm               tolerance_mass                grad_ree

   The damping factor model automatically chooses the most appropriate values of these parameters based
   on the type of machine and the grid. You would typically specify the following values for this section:
    0.00 0.00 0.00 0.00 0.00 1.00


   Parameter              Description
   damp_sc                Damping factor for streamline curvature terms.

                          Note:
                          •     The Wilkinson stability analysis for streamline curvature
                                programs indicates that the streamline curvature damping
                                term has to be reduced for long closely spaced quasi-or-
                                thogonals (high aspect ratio). For details, see the section
                                on computational grid (Computational Grid (p. 144)).
                          •     If damp_sc = 0.0 then the program determines the value
                                of damping factor from the theory of Wilkinson, or uses
                                0.25, whichever is smaller.
                          •     Typically values of damp_sc between 0.05 and 0.25 are
                                used, but lower values may be necessary for high aspect
                                ratio quasi-orthogonals (as in end stages of steam tur-
                                bines).
                          •     If the specified value of damp_sc is larger than the value
                                predicted by the Wilkinson stability theory then the pro-
                                gram automatically reduces the damping factor to a stable
                                value.
                          •     If the program has convergence problems with an increas-
                                ing error then the value is automatically reduced internally
                                within the program during the convergence process.


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     Parameter            Description
                          •     Several different schemes for the damping are applied.
                                The original scheme is obtained with a value of damp_sc
                                between 1.0 and 1.25. New schemes which are more
                                stable and robust in most cases can be obtained with the
                                value of damp_sc between 0.0 and 0.25. A value between
                                or 2.0 and 2.25 uses the original scheme with changed
                                constants. The first digit then defines which scheme is
                                used (0 - original, 1 - modified original, 2 - new scheme)
                                and the digits after the decimal point are the damping
                                factor itself.
     damp_vl              Damping factor on velocity level. Note this damping factor
                          is also used internally in the program for all parameters which
                          are under-relaxed.

                          Notes:
                          •     There is no stability theory to define this, and a typical
                                value used is 0.50, indicating that 50% of the new para-
                                meter together with 50% of its original value is used.
                          •     If damp_vl = 0.0 then 0.50 is used.
     cm_start             Value of meridional velocity on the mean streamline as a
                          fraction of u_ref, as used in the initial conditions. This is
                          then a sort of flow coefficient (cx/u) of the device concerned
                          and is used as a guide to the velocity levels that can be ex-
                          pected.

                          Notes:
                          •     Recommended that this should be less than the actual
                                value when converged because this avoids choking during
                                the early streamline curvature iterations.
                          •     If simulations from a cold-start (with no restart file) fail to
                                converge, it may be useful to modify this parameter be-
                                cause it strongly influences the start velocities.
                          •     Not used if the restart initial condition is used.
                          •     If cm_start = 0.0 then 0.25 is used for all calculations
                                except radial turbines where 0.1 is used. The value of 0.25
                                is probably adequate for radial compressors only.
     tolerance_cm         Tolerance level on change in meridional velocity during
                          streamline curvature iterations. The value specified is the
                          maximum percentage change in meridional velocity for con-
                          vergence. Iterations stop when all streamlines and all quasi-
                          orthogonals have a lower value than this.

                          Notes:
                          •     Typical value 0.01 (that is, 0.01%, which is 1 part in
                                10,000).
                          •     If tolerance_cm = 0.0 then 0.01% is used.


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                                                                                                                 Screen Output Files (screen.scn)

    Parameter               Description
                            •     Note that if the meridional velocity is low at a certain
                                  point in the flow field, it may be necessary to use a
                                  higher value than this.
                            •     Note that the extremely low value of 0.01% does not imply
                                  that the solution is as accurate as this, but just provides
                                  confidence that convergence has really been achieved.
    toler-                  Tolerance level on mass flow for internal mass flow iteration.
    ance_mass               Note that because this controls the convergence of the inner-
                            most loop, it should be a factor of 2 to 10 lower than the
                            tolerance value for the meridional velocity (above).

                            Notes:
                            •     Typical value 0.001 (that is 0.001%, which is 1 part in
                                  100000).
                            •     If error_max = 0.0 then 0.001% is used.
    grad_ree                Factor to reduce the spanwise velocity gradient from the ra-
                            dial equilibrium equation. Normally equal to 1.0 indicating
                            that the gradient from the radial equilibrium equation is used
                            without change. For calculations with i_ree = 3, if
                            grad_ree is set to 0.0, the program takes a meridional ve-
                            locity gradient of 0.0 (that is constant meridional velocity
                            across the span) and a value between 1.0 and 0.0 reduces
                            the spanwise gradient of meridional velocity determined by
                            the radial equilibrium equation by this amount.

Specification of the Geometry Data File (*.geo)
The geometry data file includes sections of text lines that help you to identify the parameters defined here.
You should read the section on geometry in Appendix A: A Note on Sign Convention for Angles and Velocit-
ies (p. 127) to become familiar with sign conventions and angle definitions used in this file. An example of
a geometry data file is given in Appendix C: Example of a Geometry Data File (*.geo) for a Radial Impeller (p. 130).

Section 1: Character strings identifying the geometry data (max 72 characters/line)
   The syntax is:
     Character string - title(1)
     Character string - title(2)
     Character string - title(3)

Section 2: Number of quasi-orthogonal lines and scale factor (one line)
   The syntax is:
     n_qo    scale


    Parameter               Description
    n_qo                    n_qo = number of quasi-orthogonal lines from inlet to outlet
                            of the domain. From version V1.31 onwards the maximum
                            value of this parameter is unlimited.
    scale                   The scaling factor for all geometry data that is input.

                            Notes:

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     Parameter              Description
                            •     Usually the geometry data is input in SI units (that is, all
                                  values are expected in m and not mm) and then this value
                                  is 1.0.
                            •     If the input geometry data comes from a CAD system
                                  then it may be in mm. In this case, the value of scale
                                  must be 0.001. Similarly the value can be adjusted to allow
                                  the geometry data to be input in other systems of units;
                                  for example, inches.
                            •     This scale factor only scales the data in the geometry input
                                  file and has no effect on other dimensions elsewhere; for
                                  example, it does not scale the reference diameter, which
                                  must be input with units of metres, in the aerodynamic
                                  file.
                            •     If you specify scale = 0.0, unity is used.

     For each quasi-orthogonal, the following data is required to define the flow channel for the meridional
     through-flow calculation and the meridional spacing of the quasi-orthogonals. Note that some of this
     data is also repeated in the section on the blade geometry. This duplication allows calculations to be
     made in a channel that is not the same as the hub and casing line of the actual blade definition (blade
     cropping).
Section 3: Definition of quasi-orthogonal types and end points (n_qo lines: i = 1 to n_qo)
   The syntax (of a single line) is:
      i    r_hub(i)   r_shr(i)           z_hub(i)            z_shr(i)            n_blade(i)             n_curve(i)              i_type(i)   i_row(i)   i_spool(i)


     Parameter              Description
     i                      Number of a particular quasi-orthogonal line.

                            Notes:
                            •     The actual value is not used by the program internally
                                  because it recounts the quasi-orthogonals as they are in-
                                  put. The number specified is only used as a guide to the
                                  location in the input file.
                            •     This allows you to merge two different geometry files of,
                                  say, a rotor and stator, to a single stage geometry file
                                  without the need to renumber the quasi-orthogonals. In
                                  this case, the same number may appear more than once.
                                  In a similar way, a single quasi-orthogonal may be re-
                                  moved without the need for renumbering the lines.
     r_hub(i)               Radial coordinate at hub end of quasi-orthogonal [m].
     r_shr(i)               Radial coordinate at casing end of quasi-orthogonal [m].
     z_hub(i)               Axial co-ordinate at hub end of quasi-orthogonal [m].
     z_shr(i)               Axial co-ordinate at casing end of quasi-orthogonal [m].
                            Notes on co-ordinates:
                            •     r_hub may not be close to zero; adapt the grid if neces-
                                  sary to avoid small values of r_hub.


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                                                                                                        Screen Output Files (screen.scn)

Parameter          Description
                   •     The aspect ratio of the quasi-orthogonal lines determines
                         the stability of the solver. The lines should not be too
                         closely spaced.
                   •     The end coordinates of the leading and trailing edges of
                         blade rows should be included in the list of coordinates.
                   •     The end coordinates of the leading edge of a splitter vane
                         should be included in the list of coordinates.
n_blade(i)         Number of blades in blade row.

                   Notes:
                   •     = 0 in duct regions.
                   •     The number of blades changes at a splitter blade leading
                         edge in a compressor or at a splitter vane trailing edge
                         in a turbine, and changes again for multiple splitters. This
                         is the only information that the program has about the
                         splitters, so the location of the splitter vane leading or
                         trailing edge needs to be a quasi-orthogonal line in the
                         input data.
n_curve(i)         Number of defining points along the ith quasi-orthogonal
                   line.

                   Notes:
                   •     = 1, a special case for duct stations. This indicates that
                         there are 2 defining points (as for n_curve(i) =2) but
                         that no further information for this calculating station is
                         provided in section 4 below, because it is already fully
                         defined by the hub and casing points given in section 3.
                   •     = 2 for a linear calculating plane in which only the end
                         points of the quasi-orthogonal are defined. In this case,
                         similar information can be found in section 4.
                   •     > 2 for a non-linear or curved calculating plane.
                   •     The number of defining points can vary from station to
                         station but n_curve(i) should typically be the same
                         for all stations because streamline section data is usually
                         available on a fixed number of spanwise sections.
                   •     Note that the hub and casing geometry information does
                         not necessarily have to be the same as that defined in
                         section 4. In this case the data in section 3 will be used
                         to crop the blade row or to make a section through the
                         blade information in section 4.
i_type(i)          Parameter to identify type of calculating station:

                   1 - for duct region

                   2 - for non-rotating blade row (stator)

                   3 - for rotating blade row (rotor)

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     Parameter         Description
                       Notes:
                       •     The program internally identifies which lines are leading
                             and trailing edges from the changes of type of blade row,
                             and which line is the leading edge of a splitter vane (by
                             the change in blade number).
                       •     There must be at least two duct calculating stations up-
                             stream of the first blade row, and downstream of the last
                             blade row.
                       •     A blade row must consist of at least two calculating sta-
                             tions (leading and trailing edge). Typically a radial impeller
                             will have around 15 calculating stations, because this
                             gives a 6° turn between each station and improves the
                             calculation of the curvature terms.
                       •     There must be at least two blade calculating stations up-
                             stream and downstream of a splitter vane leading edge.
                       •     Other types of blade row may be defined at a later stage.
     i_row(i)          This parameter is used to identify type of blade row and stage
                       of the quasi-orthogonal calculating station. In fact the pro-
                       gram can usually identify the type of blade row itself from
                       the geometry and the context, so it is not necessary to specify
                       these values at all and, in the first instance, this parameter
                       may be set to zero. They are included here for special cases
                       where the program may have difficulty with the rules that
                       are coded to identify blade row types.

                       = n11 - radial compressor inlet guide vane1

                       = n12 - radial compressor inlet guide vane2

                       = n13 - radial compressor impeller blade

                       = n14 - radial compressor diffuser vane

                       = n15 - radial compressor return channel vane

                       = n16 - radial compressor axial de-swirl vane

                       = n21 - axial compressor inlet guide vane1

                       = n22 - axial compressor inlet guide vane2

                       = n23 - axial compressor rotor blade

                       = n24 - axial compressor stator vane

                       = n25 - axial compressor outlet guide vane

                       = n31 - radial turbine inlet guide vane1

                       = n32 - radial turbine inlet guide vane2


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                                                                                                             Screen Output Files (screen.scn)

Parameter               Description
                        = n33 - radial turbine impeller blade

                        = n34- radial turbine stator vane

                        = n35- radial turbine outlet guide vane

                        = n41 - axial turbine inlet guide vane1

                        = n42 - axial turbine inlet guide vane2

                        = n43- axial turbine rotor blade

                        = n44- axial turbine stator vane,

                        = n45- axial turbine outlet guide vane

                        Notes:

                        The value of n determines which stage is being considered,
                        such that a multistage axial compressor with an IGV would
                        begin with values of 121 for the inlet guide vane, continue
                        with values of 123 for the rotor, and 124 for the downstream
                        stator, so that the next rotor would be 223, an so on. A
                        double row of stators would be denoted as n24 and n25 for
                        the successive blade rows.
i_spool                 Parameter to identify rotational speed of spool or shafts
                        where different blade rows have different speeds.

                        0 single shaft with one speed (ref_n)

                        1 first shaft with speed (ref_n1)

                        2 second spool with second speed (ref_n2)

                        3 third spool with third speed (ref_n3)

                        Note that counter-rotating blade rows can be dealt with by
                        specifying negative speeds for the second spool. The program
                        determines the number of different spools (n_spool) from
                        the number of different values of i_spool(i) found in the
                        geometry input file. (The maximum is set to be 3.)

Notes:
 •   The data is supplied on n_curve lines spaced fairly evenly from hub to casing. For example, if
     n_curve = 5, there may be points at 0%, 25%, 50%, 75%, and 100% of span. If n_curve = 2, there
     will be just two points, at 0% and 100% span.
 •   The blade data and quasi-orthogonal data in section 4 may extend outside of the flow channel
     defined by the meridional coordinates given in section 3. In a normal calculation, the data overlaps
     partly with that given in section 3, because the end points of the quasi-orthogonal lines are defined
     twice (except for duct calculating stations with n_curve(i) = 1; see above). The flow channel
     defined in section 3 is generally congruent with the blade hub and shroud defined in section 4. The
     blade, as defined in section 4, may extend outside of the region of the flow channel because this

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           allows a calculation to be made in a cropped or trimmed flow channel only by changing the data
           in section 3; section 4 does not need to be changed.
     •     The end points of the quasi-orthogonal lines, as defined by coordinates r_hub(i), r_shr(i),
           z_hub(i), and z_shr(i), should lie along the quasi-orthogonal lines as defined by r_qo (j,i)
           and z_qo(j,i) below. In many cases, the end points will be coincident with the blade data, but
           if this is not the case, it is not acceptable to define end points that do not lie on the blade data
           point.
     •     All the angles are specified in degrees because this is more convenient in those cases where it may
           be necessary to define the geometry by hand, and also allows a simple consistency check, but in-
           ternally the program converts them into radians. Further description of the angles is provided in
           Appendix A: A Note on Sign Convention for Angles and Velocities (p. 127).

           The sections above define only the hub and casing walls and provide information on the type of
           calculating station. The detailed orientation and position of the curved quasi-orthogonal line and
           the details of the blade surface geometry are provided in the next section.
Section 4: Geometry of quasi-orthogonal line and blade
   The syntax (of the single line) is:
     i      j   r-qo(j,i)         theta_qo(j,i)              z_qo(j,i)             thu_qo(j,i)              gamma_r_qo(j,i)           gamma_z_qo(j,i)


     Parameter                Description
     i                        Number of a particular quasi-othorgonal for data input (in-
                              creasing from inlet to outlet). Note that this value is not read
                              in as input data but is simply used as orientation in the data
                              file when examining the geometry input data.
     j                        Number of streamline for data input (increasing from hub to
                              shroud). Note that this value is not read in as input data but
                              is simply used as orientation in the data file when examining
                              the geometry input data. Note that for each q-o (i), the
                              spanwise data is entered (j) before continuing with the
                              next q-o.
     r_qo(j,i)                Radial coordinate of point j along q-o (i) [m].
     theta_qo(j,i)            Circumferential coordinate of blade camber line at point
                              (r_qo, z_qo) [degrees].

                              Note:
                              •     The angular coordinate (theta) is taken as positive in the
                                    direction of rotation and negative in the other direction.
                              •     In a duct region this angle may be zero.
                              •     This angle is not used by the program but helps to visu-
                                    alize the blade shape and may be useful for plots of the
                                    blade shape.
                              •     In a region where there is a splitter vane this angle is the
                                    blade camber angle of the main blade and not of the
                                    splitter.
     z_qo(j,i)                Axial coordinate of point along quasi-orthogonal [m].
     thu_qo(j,i)              Circumferential thickness of blade at point (r_qo, z_qo) [m].



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                                                                                                             Screen Output Files (screen.scn)

Parameter               Description
                        Note:
                        •     In a duct region this thickness should be specified as zero.
                        •     In a region where there is a splitter vane this thickness is
                              the mean thickness of the main blade and the splitter.
                        •     At leading and trailing edges the value supplied is not
                              used by the program, but the calculating station is taken
                              to be at the limit of the chord with zero thickness.
                        •     The thickness is not the thickness normal to the camber
                              line.
gamma_r_qo(j,i)Lean angle of the blade with a radial line [degrees] as defined
               in Appendix A: A Note on Sign Convention for Angles and Velo-
               cities (p. 127).
gamma_z_qo(j,i)Lean angle of the blade with an axial line [degrees] as defined
               in Appendix A: A Note on Sign Convention for Angles and Velo-
               cities (p. 127).

Notes:
 •   This geometry includes the coordinates of the blade camber surface (r-qo(j,i), theta_qo(j,i),
     z_qo(j,i)) so that it would theoretically be possible for the program to differentiate this inform-
     ation to determine the slope angles of the surface (gamma_r_qo(j,i), gamma_z_qo(j,i)).
     This is not done for two reasons. Firstly, experience shows that with the crude grids typically used
     for throughflow calculations, this differentiation would be an unwanted source of error leading to
     poor estimates of the blade angles, so a system was chosen in which the blade angles are supplied.
     In fact the value of theta_qo(j,i) is not used by the program and can be specified as zero.
     Secondly, in many cases the slope angles of a blade row are known (inlet and outlet angles)
     whereas the circumferential coordinate is unknown.
 •   This system of geometry with the definition of two angles is designed for radial turbomachinery
     applications because it allows the complex shape of three-dimensional blades to be defined by the
     use of the two lean angles, gamma_r and gamma_z.
 •   In conventional axial turbomachinery throughflow programs, it is not usual to define the blade in
     much detail because often simulations are carried out with only inlet and outlet blade angles. This
     is also possible with Vista TF. In a ductflow calculation with only leading and trailing edges, the
     value of gamma_r can be set to 0°. Because the leading and trailing edges are not considered to
     have any blade force, this has no effect on the simulation. The value of gamma_z defines the inlet
     and outlet blade angles of sections through the blade at constant radius.
 •   Vista TF assumes that the geometry is always specified for a clockwise rotation (see Appendix A: A
     Note on Sign Convention for Angles and Velocities (p. 127)). If the geometry is correctly specified, a
     negative rotational speed is used, and Vista TF performs calculations assuming that the shaft is ro-
     tating in the wrong direction with all the wrong incidences, loading, an so forth. For the case where
     the geometry is specified for counterclockwise rotation, the value of i_flow in the .con file should
     be specified as a negative number, for example, -1 or -2. This causes the program to internally switch
     the angles from positive to negative, and vice-versa, before it proceeds to perform calculations as
     usual, assuming that the shaft rotates in the clockwise rotation.
 •   The next sections provide additional blade-row geometry data for use by the correlations in the
     program. Although this data is not always needed, the format of this section includes 8 real para-
     meters.


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Section 5: Additional geometry data (n_curve(i) lines for each blade row)
   The syntax is:
     j     throat   throat_pos          clearance             max_thickness               te_thickness               dummy         dummy   dummy


     Parameter             Description
     j                     Number of a particular streamline for data input (increasing
                           from hub to shroud).
     throat                Throat width of section j [m].

                           Note:
                           •     If the value of zero is input then the program estimates
                                 the throat width from the blade angles and the blade
                                 thickness, taking into account that the throat is close to
                                 the leading edge for compressors and close to the trailing
                                 edge for turbines. For radial compressors this estimate is
                                 not particularly accurate and for cases close to choke you
                                 should provide more precise data here.
                           •     For axial compressors it is assumed that the blade has a
                                 circular arc camber line and the program includes an es-
                                 timate of the throat area based on the geometrical rela-
                                 tionships for circular arc blades.
                           •     For other blade types, you should specify the value.
     throat_pos(i)         Position of throat on this blade section.

                           Note:
                           •     If the value of zero is input then the program estimates
                                 the throat position from the blade angles and the blade
                                 thickness, taking into account that it is close to the leading
                                 edge for compressors and close to the trailing edge for
                                 turbines.
                           •     For radial compressors this estimate is not particularly
                                 accurate and for cases close to choke you should provide
                                 more precise data here.
                           •     For axial compressors it is assumed that the blade has a
                                 circular arc camber line and the program includes an es-
                                 timate of the throat position based on the geometrical
                                 relationships for circular arc blades.
                           •     For other blade types, you should specify the value.
     tip clearance         Tip clearance of hub section [m].

     hub/shroud            Tip clearance of shroud section [m].

                           Note:
                           •     If the first value is non-zero, this is interpreted as the hub
                                 clearance.
                           •     If the last value (n_curve(i)) is non-zero, this is inter-
                                 preted as the casing clearance.


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                                                                                                                Screen Output Files (screen.scn)

    Parameter              Description
                           •     In a variable stator vane with a hub clearance and a
                                 clearance gap for the shaft, it is possible to have non-zero
                                 values on both the hub and the tip and then both will
                                 be taken into account in the loss correlations.
    max_thickness          Maximum normal thickness of blade section [m].

                           Note:
                           •     Although the circumferential thickness of the blade row
                                 is already specified in section 3, the location of the quasi-
                                 orthogonal lines may not coincide with the location of
                                 normal maximum thickness, so this value must be spe-
                                 cified separately.
                           •     If the value of zero is specified then the program searches
                                 for the normal maximum thickness of the blade, as given
                                 in section 3, and uses it.
    te_thickness           Trailing edge normal thickness of blade section [m].

                           Note:
                           •     Although the circumferential thickness of the blade row
                                 is already specified in section 3, this value must be spe-
                                 cified separately.
                           •     If the value of zero is specified then the program estimates
                                 the trailing-edge thickness of the blade from the circum-
                                 ferential thickness given in section 3, and uses it.
    dummy                  In order to allow for parameters that may be needed by
                           other correlations in the future, the program includes three
                           dummy parameters which should each be set to 0.0.

Specification of Aerodynamic Data File (*.aer)
The aerodynamic input data file includes lines of text that help you to identify the parameters defined here.
Although in some areas this file may appear to be complex, a typical simulation uses only one of the allowed
options and so, once an input file with the correct format has been established, further use of the file is less
complex.

An example of an aerodynamic data file is given in Appendix D: Example of an Aerodynamic Data File
(*.aer) (p. 132).

Section 1: Character strings identifying the aerodynamic data (max 72 characters/line)
   The syntax is:
    Character string – title(1)
    Character string – title(2)
    Character string – title(3)

   Many options are supplied for specifying the flow data, but typically the options with i_flow = 1
   (specified mass flow) and i_flow = 5 (specified pressure ratio) are used. Note that i_flow is specified
   in the control file.
Section 2: Reference aerodynamic parameters (depends on value of i_flow in .con file)
   The syntax is:

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     ref_mach         ref_phi                 ref_d

     if i_flow = 0 and ref_mach < 3, or

     ref_u      ref_phi                ref_d

     if i_flow = 0 and ref_u > 3, or

     ref_n      ref_mass                  ref_d

     if i_flow = 1 and n_spool = 0 or 1, or

     ref_n1      ref_n2                ref_mass                   ref_d

     if i_flow = 1 and n_spool = 2, or

     ref_n1      ref_n2                ref_n3                 ref_mass                  ref_d

     if i_flow = 1 and n_spool = 3, or

     ref_n      ref_volume                    ref_d

     if i_flow = 2, or

     ref_u      ref_mass                  ref_d

     if i_flow = 3, or

     ref_u      ref_volume                    ref_d

     if i_flow = 4, or

     ref_n      ref_mass                  ref_d               ref_pr

     if i_flow = 5, or

     ref_n      ref_mass                  ref_d               ref_pr                n_p_te                guess_pr_1                   ...

     if i_flow = 6, or

     ref_n      ref_mass                  ref_d               ref_pd

     if i_flow = 7, or

     ref_n      ref_mass                  ref_d               ref_pd                n_p_te                guess_pd_1                   ...

     if i_flow = 8, or

     ref_n      ref_mass                  ref_d               ref_cu

     if i_flow = 9.




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                                                                                                          Screen Output Files (screen.scn)


   Note

   The very large number of possible ways of specifying the flow and speed appears, at first, to
   be slightly overwhelming. Generally i_flow = 1 is used. Note that the reference diameter
   is given here and not in the geometry file. This is because you may prefer to use the hub
   diameter, the tip diameter, the inlet diameter, or the outlet diameter, as a reference value
   without changing the geometry file.


   Note

   The geometry definition of Vista TF assumes clockwise rotation. This leads to a certain con-
   vention for the sign of the blade angles (see Appendix A: A Note on Sign Convention for Angles
   and Velocities (p. 127)). In some cases you may have a counterclockwise machine with blade
   angles of the opposite sign. To avoid the need to change all the angles specified in the .geo
   file, an option is provided whereby the value of i_flow is given a negative sign.

   A negative value for speed means that the blade is rotating in the counterclockwise direction.




Parameter            Description
i_flow=0             “Iteration to mass flow”

                     ref_mach = Machine Mach number (based on inlet total
                     conditions) [-] or reference blade speed [m/sec]. (In this doc-
                     ument, “[-]” means dimensionless.)

                     Notes:
                     •     If ref_mach < 3 then ref_mach is interpreted as
                           ref_mach.




                     •     If ref_mach > 3 then ref_mach is interpreted as
                           ref_u.




                     ref_phi = Inlet flow coefficient (based on total inlet condi-
                     tions) [-]. (In this document, “[-]” means dimensionless.)




                     ref_d = Reference blade diameter for the definition of flow

                     coefficient.                [m]
i_flow=1             “Iteration to mass flow”


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     Parameter         Description
                       ref_n = Machine rotational speed [rpm]

                       ref_mass = Mass flow [kg/sec]

                       ref_d = Reference blade diameter for the definition of flow

                       coefficient.                [m]

                       If the machine has separate spools of different speeds
                       (i_spool(i) > 2) then the speed of each spool can be
                       provided up to a maximum of three different spools.

                       ref_n1 = Rotational speed of shaft 1 [rpm]

                       ref_n2 = Rotational speed of shaft 2 [rpm]

                       ref_n3 = Rotational speed of shaft 3 [rpm]

                       Counter-rotating blade rows require the second blade row
                       to be provided with a negative speed.
     i_flow=2          “Iteration to mass flow”

                       ref_n = Machine rotational speed [rpm]

                       ref_volume = Volume flow at inlet total conditions [m3/sec]

                       ref_d = Reference blade diameter for the definition of flow

                       coefficient.                [m]
     i_flow=3          “Iteration to mass flow”

                       ref_u = Reference blade speed [m/s]

                       ref_mass = Mass flow [kg/sec]

                       ref_d = Reference blade diameter for the definition of the
                       blade speed [m]
     i_flow=4          “Iteration to mass flow”

                       ref_u = Reference blade speed [rpm]

                       ref_volume = Volume flow at inlet total conditions [m3/sec]

                       ref_d = Reference blade diameter for the definition of the
                       blade speed [m]
     i_flow=5          “Iteration to pressure ratio”

                       ref_n = Machine rotational speed [rpm]

                       ref_mass = Mass flow [kg/sec] (estimate of actual mass
                       flow but final converged mass flow is determined by the
                       pressure ratio and this only serves as an initial guess)


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                                                                                                       Screen Output Files (screen.scn)

Parameter         Description
                  ref_d = Reference blade diameter for the definition of flow

                  coefficient.                [m]

                  ref_pr = Total to static pressure ratio on mean streamline
i_flow=6          “Iteration to pressure ratio”

                  ref_n = Machine rotational speed [rpm]

                  ref_mass = Mass flow [kg/sec] (estimate of actual mass
                  flow)

                  ref_d = Reference blade diameter for the definition of flow

                  coefficient.                [m]

                  ref_pr = Total to static pressure ratio on mean streamline

                  n_p_te = Number of trailing edges at which a guessed value
                  of the pressure ratio is specified

                  guess_pr_1 = Guessed value of the pressure ratio at the
                  first trailing edge

                  guess_pr_2 = Guessed value of the pressure ratio at the
                  second trailing edge

                  ...

                  guess_pr_n_p_te = This continues up to and including
                  the last trailing edge.

                  Note that if the pressure ratio of the last trailing edge differs
                  to that of ref_pr, than all values at all trailing edges are
                  scaled with the value of ref_pr.
i_flow=7          “Iteration to pressure difference”

                  ref_n = Machine rotational speed [rpm]

                  ref_mass = Mass flow [kg/sec] (estimate of actual mass
                  flow but final converged mass flow is determined by the
                  pressure ratio and this only serves as an initial guess)

                  ref_d = Reference blade diameter for the definition of flow

                  coefficient.                [m]

                  ref_pd = Total to static pressure difference on mean
                  streamline
i_flow=8          “Iteration to pressure difference”

                  ref_n = Machine rotational speed [rpm]



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     Parameter         Description
                       ref_mass = Mass flow [kg/sec] (estimate of actual mass
                       flow)

                       ref_d = reference blade diameter for the definition of flow
                       coefficient                 [m]

                       ref_pd = Total to static pressure difference on mean
                       streamline

                       n_p_te = Number of trailing edges at which a guessed value
                       of the pressure ratio is specified

                       guess_pd_1 = Guessed value of the pressure difference at
                       the first trailing edge

                       guess_pd _2 = Guessed value of the pressure difference
                       at the second trailing edge

                       ...

                       guess_pd_n_p_te = This continues up to and including
                       the last trailing edge
     i_flow=9          “Iteration to outlet swirl”

                       ref_n = Machine rotational speed [rpm]

                       ref_mass = Mass flow [kg/sec] (estimate of actual mass
                       flow)

                       ref_d = reference blade diameter for the definition of flow

                       coefficient.                [m]

                       ref_cu = Swirl velocity on mean streamline at rotor outlet




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                                                                                                                 Screen Output Files (screen.scn)


        Note
         •    The reference blade speed, tip speed Mach number, or Machine rotational speed is also
              needed for the calculation of a stator blade row. This is because these parameters are
              used to define various non-dimensional flow and work coefficients and the reference
              blade speed is also used to determine the flow velocities for the initial estimate of the
              flow field (together with parameter cm_start. See section 5 of the .con file specification
              given in Specification of the Control Data File (*.con) (p. 74)).
         •    Iteration to a defined pressure ratio makes use of the so-called target pressure ratio
              method of Denton. This requires the program to make a fist guess of the pressure at
              each trailing edge of the machine. The algorithm currently incorporated makes a crude
              estimate of these, but it has been found that this may not be sufficient to secure conver-
              gence. For this reason, you can define the first guess of the pressure at each trailing edge
              by setting i_flow = 6 (instead of 5).
         •    A line prepared with data for i_flow = 6 can formally also be used with i_flow = 5
              or i_flow =1 with no change, so that a calculation can switch from “iteration to pressure
              ratio” to “iteration to mass flow” with no formal change to the aerodynamic input data
              file.



Section 3: Reynolds number or viscosity
   The syntax is:
    ref_re

   or
    ref_mue


    Parameter               Description
    ref_re
                            Reynolds number based on ref_u (             ), ref_D (      ),
                            and inlet total conditions [-]. (In this document, “[-]” means
                            dimensionless.)




    ref_mue                 Dynamic viscosity                   at the inlet plane and mean inlet total
                            conditions.




        Note

        The program identifies which of these parameters has been provided from the absolute value
        of the numerical input. If the value is greater than 1.0 [N s m^-2] (or equivalent value in other
        units), it is interpreted as a Reynolds number; if it is less than 1.0 [N s m^-2] but greater than
        0.0000001 [N s m^-2], it is interpreted as the dynamic viscosity. A value of 0 causes the program
        to determine the dynamic viscosity from an inbuilt equation for the dynamic viscosity based
        on Sutherland’s law and the inlet total temperature.


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Section 4: Fluid data (depends on value of i_fluid in .con file)
   The syntax is:
      cp_gas       gamma_gas

     if i_fluid = 1, which indicates an ideal gas, or
      cw_fluid       rho_fluid

     if i_fluid = 2, which indicates a liquid.

     Parameter                 Description
     i_fluid = 1               cp_gas = Specific heat at constant pressure [J/kgK]

     (ideal gas)

                               gamma_gas = ratio of specific heats [-] (In this document,
                               “[-]” means dimensionless.)




     i_fluid = 2               cw_fluid = Specific heat of fluid [J/kgK]

     (liquid)

                               rho_fluid = density of liquid [kg/m3]



Section 5: Number of points on the inlet boundary where flow conditions are specified
   The syntax is:
      n_inbc


     Parameter                 Description
     n_inbc                    Number of points at which the inlet flow conditions are spe-
                               cified across the inlet plane.

                               Note:
                               •     n_inbc < n_sl
                               •     if n_inbc = 1 then only a single value is input and the
                                     values are constant across the span



Section 6: Fraction of mass flow where inlet conditions are specified (n_inbc values)
   The syntax is:
      f_mass_inbc




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                                                                                                                  Screen Output Files (screen.scn)

    Parameter                Description
    f_mass_inbc              n_inbc values of the fraction of mass along the inlet
                             boundary at which inlet boundary conditions are specified.
                             First value should be 0.0 and last value should be 1.0. Note
                             that if n_inbc = 1 then this has no function and a dummy
                             value can be specified, but this should not be omitted.



Section 7: Pressure on the inlet boundary (n_inbc values which depend on i_inbc in .con file)
   The syntax is:
    pt_inbc

   if i_inbc = 0.

    Parameter                Description
    pt_inbc                  Total pressure on the inlet boundary [Pa].

    (i_inbc=0)               Note that if an incompressible calculation is carried out it is
                             still necessary to specify the absolute value of the total pres-
                             sure on the inlet boundary.



Section 8: Temperature on the inlet boundary (n_inbc values, depend on i_inbc in .con file)
   The syntax is:
    tt_inbc

   if i_inbc = 0.

    Parameter                Description
    tt_inbc                  Total temperature on the inlet boundary [K].

    (i_inbc = 0)



Section 9: Swirl or angle on the inlet boundary (n_inbc values, depend on i_inbc in .con file)
   The syntax is:
    rcu_inbc

   if i_inbc = 0, or
    alpha_inbc

   if i_inbc = 1.

    Parameter                Description
    rcu_inbc                 Swirl on the inlet boundary [m2/sec]. Note that this is the
                             product of the local radius of the streamline and the local
    (i_inbc=0)               circumferential velocity component and is positive if the swirl
                             is in the forward direction of rotation.


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      Parameter              Description
      alpha_inbc             Flow angle on the inlet boundary [°]. Note that this is from
                             the axial direction and positive in the direction of rotation.
      (i_inbc=1)             Note also that, if a single value is specified, it is used to calculate
                             the swirl on the mean streamline of the inlet boundary, and this
                             swirl is then kept constant across the span. If a constant angle
                             across the span is required then 2 values need to be specified
                             across the span (n_inbc=2). Experience with radial turbines
                             with high swirl at the inlet show that the specification of a single
                             value of swirl across the span is more robust than specifying a
                             variation of flow angle across the span.



Section 10 : Aerodynamic model parameters
   The syntax is:
      eddy   f_bl_le      f_bl_te


      Parameter              Description
      eddy                   Spanwise mixing parameter (eddy diffusivity).

                             Notes:
                             •     Typically 0.0001 to 0.001. See Streamline Curvature
                                   Throughflow Theory (p. 118).
                             •     This has no function if i_mix = 0.
                             •     If i_mix = 1 and eddy = 0.0 then a value of eddy =
                                   0.0005 will be used.
      f_bl_le                f_bl_te is the meridional fraction of blade length at the
                             leading edge where the blade is partly transparent to the
                             flow (accounts artificially for the increased loading due to
                             incidence). It is recommended that you specify a value of 0.0
                             for both f_bl_te and f_bl_le. If both f_bl_te and
                             f_bl_le are equal to zero then the program estimates the
                             values of these from the blade spacing using the equations
                             given in Streamline Curvature Throughflow Theory (p. 118). If
                             you want, you can specify these values. If you specify 0.0 then
                             the flow is congruent with the mean blade camber line at
                             the leading edge. A typically value is roughly equal to the
                             blade spacing.
      f_bl_te                Fraction of blade length after which the blade is partly
                             transparent to the flow at the trailing edge (accounts artifi-
                             cially for the decreased loading due to deviation as the trail-
                             ing edge is approached). It is recommended that you specify
                             a value of 0.0 for both f_bl_te and f_bl_le. If you specify
                             1.0 then the flow is congruent with the mean blade camber
                             line right up to the trailing edge. If both f_bl_te and
                             f_bl_le are equal to zero then the program estimates these
                             from the blade spacing using the equations given in
                             Streamline Curvature Throughflow Theory (p. 118).


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Specification of Correlations Data File (*.cor)
The input data file includes sections of text lines that help you to identify the parameters defined here; see
the examples in Appendix E: Examples of Correlations Data Files (*.cor) (p. 133). The first part of the file contains
control parameters that define the layout of the remainder of the input data that is needed. The file is arranged
so that it always has a standard format at the beginning (first 8 lines) but may require different data towards
the end depending on the type of calculation under consideration (axial compressor, radial turbine, single
stage, multi-stage, an so on). Similar types of simulations always use similar formats for this file, but different
types of simulations may require different formats for the latter part of this file.

You specify the empirical data using one of two approaches:

 •   You specify losses, blockage, and deviation, associated with individual, specifically-defined, quasi-ortho-
     gonals.

     This approach is oriented around the quasi-orthogonals, enabling you to specify different local efficiency
     and blockage values for each quasi-orthogonal. Although deviation is only meaningful at the trailing
     edge, a similar approach is used for deviation to be consistent with losses and blockage.

     This approach is recommended for beginners.
 •   You provide information that enables the program to calculate the needed empirical data for blade
     rows from built-in correlations.

     This approach is oriented around blade rows and requires data to be specified at each blade row trailing
     edge (or upstream of this – see later).

Note that the correlations used for individual blade rows can be changed from one blade row to another.
You can also use the correlations for deviation from one source and the correlations for losses from another.
In general, and for simplicity, you should apply the correlations in such a way that all blade rows use the
same correlations and the losses, blockage, and deviation, are also from the same source.

The correlations currently programmed and in preparation can be obtained with the use of the following
parameters for i_loss_type, i_dev_type and i_ewb_type:

Turbine correla-      i_loss_type / i_dev_type / i_ewb_type
tions
Kacker-Okapuu         1/1/1
Dunham-Came           2/2/2

Compressor cor-       i_loss_type / i_dev_type / i_ewb_type
relations
Miller-Wright         11 / 11 / 11
Miller-Wright (as     12 / 12 / 12
modified by Cal-
vert)

If required, you can specify single values of the losses, deviation, and blockage parameters, for the first blade
row or first quasi-orthogonal. These are then used throughout the domain provided that they are not changed
again. In addition, it is possible to apply multiplicative and additive correction factors to the values predicted
by the correlations, by the application of “fudge factors” (user-defined corrections). Generally this file does
not need to be changed once it has been set up, so you might not need to understand all the intricacies of


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the many possibilities that it allows, and typically a standard type of correlations file can be established
which can then be used for all subsequent simulations with the same set of correlations.

Examples of some typical correlations data files are given in Appendix E: Examples of Correlations Data Files
(*.cor) (p. 133), showing several specific examples for specific types of calculation.
Section 1: Character strings identifying the correlation data (max 72 characters/line)
   The syntax is:
      Character string – title(1)
      Character string – title(2)
      Character string – title(3)

Section 2: Integer control parameters for loss, deviation and blockage models (one line)
   The syntax is:
      i_loss   i_dev      i_ewb


      Parameter              Description
      i_loss                 Determines the loss specification to be used.

                             Notes:
                             •     i_loss = 0

                                   No losses are specified and the calculation uses constant
                                   entropy. Note, however, that in order to retain similar
                                   structures for the correlations file, the lines described in
                                   sections 3 and 4 are still needed, but have no effect.
                             •     If i_loss = 1 then a user-defined variation of efficiency,
                                   loss coefficient, or dissipation coefficient across the span
                                   is specified at the spanwise positions given in section 4.
                                   The number of definition positions across the span and
                                   through the domain are given in section 3. Different val-
                                   ues of the efficiency, loss coefficient, or dissipation coeffi-
                                   cient can be specified for different quasi-orthogonal cal-
                                   culating stations. A value on the first quasi-orthogonal is
                                   always needed. This value remains constant until changed
                                   by the next quasi-orthogonal at which the loss is defined.
                                   If only a single value is specified across the span then this
                                   is applied on the mean streamline and each streamline
                                   has the same entropy rise as on the mean streamline. If
                                   a calculation with a constant efficiency for all streamlines
                                   is required then the efficiency needs to be specified con-
                                   stant on at least two points across the span.
                             •     If i_loss = 2 then built-in loss correlations are used ac-
                                   cording to the values given in sections 3 and 4.
      i_dev                  Determines the method for calculation of a blade outlet flow
                             angle (deviation or slip).

                             Notes:
                             •     If i_dev = 0 , the flow follows the mean blade camber
                                   line given in the .geo file with no deviation. This option
                                   allows a mean S2 though-flow calculation to be carried


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    Parameter               Description
                                  out using the mean stream surface obtained from a series
                                  of S1 blade-to-blade calculations, provided that these are
                                  then given as the geometry of the camber surface in the
                                  .geo file. Note that, in order to retain similar structures
                                  for the correlations file, the lines described in sections 5
                                  and 6 are still needed but have no effect.
                            •     If i_dev = 1 then data is specified in sections 5 and 6 to
                                  predict the variation of the flow angle at the blade outlet
                                  from the mean blade camber line across the span. The
                                  information can be either in the form of a deviation angle,
                                  a specified flow outlet angle, a specified slip factor, or a
                                  modification to the cosine rule, according to the type of
                                  blade row.
                            •     If i_dev = 2 then inbuilt correlations are used to determ-
                                  ine the flow angle according to the type of blade row as
                                  specified in sections 5 and 6.
    i_ewb                   Determines the blockage correlation for boundary layers that
                            is to be used (ewb means “end-wall blockage”)

                            Notes:
                            •     If i_ewb = 0 then no end-wall blockage is applied. Note
                                  that, in order to retain similar structures for the correla-
                                  tions file, the lines described in sections 7 and 8 are still
                                  needed, but have no effect.
                            •     If i_ewb = 1 then data is specified in sections 7 and 8 to
                                  predict the variation of the flow blockage for each quasi-
                                  orthogonal and for each streamline. A single value implies
                                  that a constant blockage value is applied in the whole
                                  calculation domain.
                            •     If i_ewb = 2 then builtin correlations are used to determ-
                                  ine the blockage according to the type of blade row as
                                  specified in sections 7 and 8.



Section 3: Loss input data locations
   The syntax is:
    n_loss_sl     n_loss_qo

   or
    n_loss_bladerow       n_dummy

   If i_loss equals 0 or 1 then the losses for each quasi-orthogonal can be specified, and the following
   values are required:

    Parameter               Description
    n_loss_sl               Number of the spanwise positions for which the loss data is
                            supplied.


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      Parameter                 Description
      n_loss_qo                 Number of quasi-orthogonal calculating stations through the
                                domain on which the loss information is specified.

      If i_loss equals 2 then the losses for each blade row can be specified, and the following values are
      required:

      Parameter                 Description
      n_loss_bladerowNumber of separate blade rows for which the loss data is
                     supplied.
      n_dummy                   A dummy integer value to ensure that line 3 always has two
                                integer values.

      If i_loss equals 0 or 1 then the following version of section 4 is required:
Section 4: User-defined loss data specification (n_loss_qo * n_loss_sl lines)
   This version of section 4 is applicable when i_loss equals 0 or 1.

      The syntax is:
       i_qo_loss       k_loss       f_loss          loss


      Parameter                 Description
      i_qo_loss                 Number of the quasi-orthogonal calculating station on which
                                the loss, deviation, and blockage information is specified. The
                                specified values will be applied for all blade rows and calcu-
                                lating stations downstream of this quasi-orthogonal until the
                                value is changed by a subsequent section 4 with a new value
                                of j_qo_loss. The first value of i_qo_loss must be 1.
                                Subsequent lines may change the way in which the losses
                                are defined.
      k_loss                    Parameter to define how the losses are specified. The value
                                of the polytropic efficiency, the loss coefficient, or the dissip-
                                ation coefficient, determines the entropy increase depending
                                on the values of k_loss.

                                Notes:
                                •     If k_loss = 1 then the small-scale static to static poly-
                                      tropic efficiency (etapoly) is specified. This is used in
                                      such a way that the entropy always increases so that, for
                                      an accelerating flow with a decrease in static enthalpy, it
                                      defines a turbine efficiency, and for a decelerating flow,
                                      it defines a compressor efficiency. This small-scale effi-
                                      ciency is applied in blade rows and in ducts.
                                •     If k_loss = 2 then the entropy loss coefficient (xsi) is
                                      specified. Note that the loss coefficient is the entropy loss
                                      coefficient with respect to outlet plane dynamic head for
                                      accelerating blade rows (turbine rotors and stators) and
                                      with respect to the inlet plane dynamic head for deceler-
                                      ating blade rows (compressor rotors and stators). An inlet
                                      guide vane for a compressor is therefore calculated as a

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    Parameter               Description
                                  turbine blade row, and an outlet guide vane for a turbine
                                  as a compressor blade row. Like the deviation, this value
                                  is only used at the trailing edge of a blade row.
                            •     If k_loss = 3 then the dissipation loss coefficient (cd)
                                  is specified. This is applied in blade rows and in ducts.
                            •     If k_loss = 4 to 9 then various forms of efficiency are
                                  used to specify the rotor blade row losses, as follows:

                                  k_loss = 4 total-total polytropic efficiency

                                  k_loss = 5 total-static polytropic efficiency

                                  k_loss = 6 static-static polytropic efficiency

                                  k_loss = 7 total-total isentropic efficiency

                                  k_loss = 8 total-static isentropic efficiency

                                  k_loss = 9 static-static isentropic efficiency

                                  These are applied in blade rows only. The full range is al-
                                  lowed, but options 6 and 9 are probably not very relevant.
                            •     If k_loss = 10 then the loss in a stator vane can be
                                  specified as a total pressure loss coefficient.
                            •     If k_loss = 11 then the performance of a stator van can
                                  be specified as a static pressure rise coefficient.

                                    Note

                                    These options have been programmed in such a
                                    way that different blade rows may have different
                                    values of k_loss.


    f_loss                  The fraction of the span at which the value of loss applies. If
                            only a single value is given, it is applied at the mean
                            streamline independent of the value of f_loss.
    loss                    Depending on the value of k_loss, this is interpreted as a
                            small-scale polytropic efficiency (etapol), a loss coefficient
                            (xsi) or a dissipation coefficient (cd).

   If i_loss equals 2 then the following version of section 4 is required:
Section 4: Correlation-based loss data specification (n_loss_bladerow lines)
   This version of section 4 is applicable when i_loss equals 2.

   The syntax (of a single line) is:
    i_loss_bladerow       i_loss_type              factor1           factor2           factor3           factor4           factor5   factor6




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      Parameter              Description
      i_loss_bladerowNumber of the blade row on which the loss information is
                     specified. The specified values will be applied for all blade
                     rows downstream of this blade row until the value is changed
                     by a subsequent section 4 with a new value of
                     i_loss_bladerow, and then this will again be applied
                     until changed. The first value must be 1.
      i_loss_type            Parameter to define which correlations are used for the blade
                             row losses. The current loss correlations incorporated into
                             the method are as follows:
                             •     i_loss_type = 1

                                   Turbine loss correlations of Kacker and Okapuu
                             •     i_loss_type = 2

                                   Turbine loss correlations of Dunham and Came
                             •     i_loss_type = 11

                                   Compressor loss correlations of Miller and Wright
      factor1 to             User-defined multiplication or addition factors to the losses
      factor6                determined by the correlations. This allows the loss correla-
                             tions to be modified to improve matching with experimental
                             or CFD data. These have different functions for the different
                             correlation systems.

                             factor1: Multiplication factor on profile losses

                             factor2: Multiplication factor on secondary losses

                             factor3: Multiplication factor on tip clearance losses

                             factor4: Multiplication of penetration of secondary losses

                             factor5: Multiplication of penetration of tip clearance losses

                             factor6: Not in use



Section 5: Deviation input data locations
   The syntax is:
       n_dev_sl n_dev_qo

      or
       n_dev_bladerow n_dummy

      If i_dev equals 0 or 1 then the deviation for each quasi-orthogonal can be specified, and the following
      values are required:




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    Parameter             Description
    n_dev_sl              Number of spanwise positions for which the flow angle data
                          is supplied.
    n_dev_qo              Number of quasi-orthogonal calculating stations on which
                          the flow angle information is specified.

   If i_dev equals 2 then the deviation flow angle data can be specified for each blade row, and the fol-
   lowing values are required:

    Parameter             Description
    n_dev_bladerow Number of separate blade rows for which the flow angle data
                   is supplied.
    n_dummy               A dummy integer value to ensure that section 5 always has
                          two integer values.

   If i_dev equals 0 or 1 then the following version of section 6 is required:
Section 6: Flow angle data specification (n_dev_qo * n_dev_sl lines)
   This version of section 6 is applicable when i_dev equals 0 or 1.

   The syntax is:
    i_qo_dev    k_dev     f_dev          dev


    Parameter             Description
    i_qo_dev              Number of the quasi-orthogonal calculating station on which
                          the deviation information is specified. The specified values
                          will be applied for all blade row trailing edges downstream
                          of this quasi-orthogonal until the value is changed by a sub-
                          sequent section 6 with a new value of i_qo_dev. The first
                          value must be 1.
    k_dev                 Determines the type of outlet flow angle calculation, as fol-
                          lows:
                          •     If k_dev = 1 then the deviation angle is specified (in de-
                                grees).
                          •     If k_dev = 2 then the relative outlet flow angle is spe-
                                cified (in degrees).
                          •     If k_dev = 3 then a slip factor is specified and applied
                                on the mean line (dimensionless). Note that if no value
                                is specified then the Wiesner slip factor is used. Only re-
                                commended for radial impellers and not for mixed flow
                                stages, which should use deviation.
                          •     If k_dev = 4 then a slip factor is applied at each radius
                                of the trailing edge (dimensionless). Note that if no value
                                is specified then the Wiesner slip factor is used. Only re-
                                commended for radial impellers and not for mixed flow
                                stages, which should use deviation.
                          •     If k_dev = 5 then a correction to the flow angle calcu-
                                lated by the cosine rule is specified. If zero is specified for


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      Parameter               Description
                                    this correction, then the cosine rule is used to calculate
                                    the relative flow angle at the outlet for all radii. If a non-
                                    zero value is specified then this modifies the flow angle
                                    by this constant amount (in degrees). A positive value
                                    increases the deviation.
      f_dev                   The fraction of the span of at which the value of the deviation
                              (and similar things) applies. If only a single value is given, it
                              is applied at the mean streamline independent of its value.
      dev                     Depending on the value of k_dev, this is interpreted as a
                              deviation angle, flow angle, slip factor, or correction to the
                              cosine rule.

      If i_dev equals 2 then the deviation for each blade row must be specified using the following version
      of section 6:
Section 6: Flow angle data specification (n_dev_bladerow lines)
   This version of section 6 is applicable when i_dev equals 2.

      The syntax is:
       i_bladerow_dev     i_dev_type             factor1           factor2            factor3           factor4           factor5     factor6


      Parameter               Description
      i_bladerow_dev Number of the blade row on which the deviation information
                     is specified. The specified values will be applied for all blade
                     row trailing edges downstream of this quasi-orthogonal until
                     the value is changed by a subsequent section 6 with a new
                     value of i_bladerow_dev. The first value must be 1.
      i_dev_type              Parameter to define which correlations are used for the blade
                              row deviations. The current deviation correlations incorpor-
                              ated into the method are as follows:
                              •     i_dev_type = 1 (Kacker Okapuu)

                                    Turbine deviation using the cosine rule.
                              •     i_dev_type = 2 (Dunham and Came)

                                    Turbine deviation using the cosine rule.
                              •     i_dev_type = 11 (Miller Wright)

                                    Compressor deviation correlations of Miller and Wright.
      factor1 to              User-defined multiplication or addition factors to the devi-
      factor6                 ations determined by the correlations. This allows the devi-
                              ation correlations to be modified to improve matching with
                              experimental or CFD data. These have different functions for
                              the different correlation systems.

                              factor1: Additive factor in degrees (°) on hub deviation

                              factor2: Additive factor in degrees (°) on mean deviation



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    Parameter              Description
                           factor3: Additive factor in degrees (°) on tip deviation

                           factor4: Not in use

                           factor5: Not in use

                           factor6: Not in use



Section 7: Blockage input data locations
   The syntax is:
    n_ewb_sl    n_ewb_qo

   or
    n_ewb_bladerow      n_dummy

   If i_ewb equals 0 or 1 then the blockage for each quasi-orthogonal can be specified, and the following
   values are required:

    Parameter              Description
    n_ewb_sl               Number of spanwise positions for which the blockage data
                           is supplied.
    n_ewb_qo               Number of quasi-orthogonal calculating stations on which
                           the blockage information is specified.

   If i_ewb equals 2 then the blockage correlation can be specified for each blade row, and the following
   values are required:

    Parameter              Description
    n_ewb_bladerow Number of separate blade rows for which the blockage is
                   supplied.
    n_dummy                A dummy integer value to ensure that section 7 always has
                           two integer values.

   If i_ewb equals 0 or 1 then the blockage for each quasi-orthogonal must be specified using the following
   version of section 8:
Section 8: End wall blockage data specification (n_dev_qo * n_dev_sl lines)
   This version of section 8 is applicable when i_ewb equals 0 or 1.

   The syntax is:
    i_qo_ewb    k_ewb      f_ewb          ewb


    Parameter              Description
    i_qo_ewb               Number of the quasi-orthogonal calculating station on which
                           the blockage information is specified. The specified values
                           will be applied for all blade rows and calculating stations
                           downstream of this quasi-orthogonal until the value is



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      Parameter               Description
                              changed by a subsequent section 4 with a new value of
                              j_qo_ewb. The first value must be 1.
      k_ewb                   Determines the type of blockage calculation. Has no effect
                              because the blockage is input in only one form as below.
      f_ewb                   The spanwise location of the value of the blockage. If only a
                              single value is given, it is applied at all streamlines.
      ewb                     End-wall boundary layer blockage is specified. A value of 0.05
                              represents 5% blockage of the flow channel by the end-wall
                              boundary layers. If zero is specified then there is no end-wall
                              boundary layer blockage. Typically a constant value is spe-
                              cified across the whole span, but this parameter can be varied
                              across the span to allow for the higher blockage in the end-
                              walls related to blade ends with tip clearance.

      If i_ewb equals 2 then the following version of section 8 is required:
Section 8: End wall blockage data specification (n_dev_qo * n_dev_sl lines)
   This version of section 8 is applicable when i_ewb equals 2.

      The syntax is:
       i_bladerow_ewb     i_ewb_type             factor1           factor2            factor3           factor4           factor5     factor6


      Parameter               Description
      i_bladerow_ewb Number of the blade row on which the blockage information
                     is specified. The specified values will be applied for all blade
                     row trailing edges downstream of this quasi-orthogonal until
                     the value is changed by a subsequent section 6 with a new
                     value of i_bladerow_ewb. The first value must be 1.
      i_ewb_type              Parameter to define which correlations are used for the blade-
                              row blockage. The current blockage correlations incorporated
                              into the method are as follows:
                              •     i_ewb_type = 1

                                    No blockage consistent with Kacker Okapuu.
                              •     i_ewb_type = 2

                                    No blockage consistent with Dunham and Came.
                              •     i_ewb_type = 11

                                    Compressor blockage correlations of Miller and Wright.
      factor1 to              User-defined multiplication or addition factors to the blockage
      factor6                 determined by the correlations. This allows the end-wall
                              blockage correlations to be modified to improve matching
                              with experimental or CFD data. These have different functions
                              for the different correlation systems.

                              factor1: Not in use

                              factor2: Not in use

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    Parameter                Description
                             factor3: Not in use

                             factor4: Not in use

                             factor5: Not in use

                             factor6: Not in use

Specification of the Output Data File (*.out)
The output data file includes lines of text in ASCII format that show the results of the simulation. The file
consists of several sections:

Section 1: Input data
   At the start of this file, a list of the input data files that were used is recorded in this file so that a record
   of the file names is available.
     INPUT DATA FILES:                   Control data file: agard.con
                                            Geometric data file: agard.geo
                                            Aerodynamic data file: agard.aer
                                            Correlation data file: agard.cor
                                            Restart data file: agard.rst
     OUTPUT DATA FILES:                  Results file: agard.out
                                            Tecplot data file: impeller.txt
                                            CFD-POST data file: agard.csv
                                            Convergence history file: agard.hst
                                            Interface output file: agard.int

Section 2: Reference data
   The program uses the input data to set up the values of various other parameters; for example, where
   the reference mass flow is specified, the reference volume flow is calculated. The values of all other
   parameters not included in the input specification are given in this section. In addition, the internal
   calculation of the damping factors is provided. Other data listed here relates to the program's own es-
   timates of the throat area and the throat position. An example is given below.

    Example radial compressor calculation:
     Reference flow parameters
     -------------------------

     Mass flow distribution across streamlines:
      0.000 0.062 0.125 0.188 0.250 0.312 0.375 0.438 0.500 0.562
      0.625 0.688 0.750 0.812 0.875 0.938 1.000

     Inlet distribution across streamlines:
      Fraction of flow: 0.00
      Total pressure: 100000.00
      Total temperature: 293.00
      Inlet swirl: 0.00

     Ideal gas calculation

     gamma_gas gas_m r_gas cp_gas
      1.400 3.500 287.200 1005.200

     ref_pt(bar) ref_tt ref_rhot ref_soundt
         1.0000 293.00 1.1884 343.23

     Reference rotational direction: clockwise

     ref_d ref_u ref_omega ref_n
     0.2700 398.10 2948.91 28160.0



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       ref_mach ref_phi ref_mass ref_volume
       1.1599 0.0667 2.3000 1.94

       ref_re ref_mue
        6963614.0 0.00001834

       ref_n1 ref_n2 ref_n3
           28160.0 0.0 0.0

       Simulation with no spanwise mixing

       Iterate to mass flow, ref_mass =                               2.30000

       First approximation of streamline positions
       taken from an earlier calculation

       Estimated max. thicknesses for blade row 1
       span 0.00000 0.17343 0.34429 0.51305 0.67879 0.84126 0.97669 1.00000
       thickne 0.00351 0.00319 0.00291 0.00266 0.00241 0.00215 0.00195 0.00191

       User-input throat widths for blade row 1
       span 0.00000 0.17343 0.34429 0.51305 0.67879 0.84126 0.97669 1.00000
       throat 0.01760 0.02137 0.02460 0.02732 0.02959 0.03141 0.03257 0.03276

       Estimated throat positions for blade row 1
       span 0.00000 0.17343 0.34429 0.51305 0.67879 0.84126 0.97669 1.00000
       throat_pos 0.00969 0.02084 0.03424 0.04835 0.06224 0.07573 0.08688 0.08882

       Empirical correlation data

                User specified losses
                User specified deviation
                No blockage specified

       Relaxation factor calculation of Wilkinson
       ------------------------------------------

       Maximum aspect ratio:                 6.0667
       at calculating station:               5
       damp_sc (user input):                 0.2500
       damp_sc (Wilkinson):                  0.0577

       Warning: damp_sc reduced by the code
                 to the value suggested by Wilkinson

Section 3: Short history of the convergence
   The .out file contains a statement about convergence of the results. A converged calculation includes
   a header such as the following:
       ***********************************************
       * Vista TF            converged -it_main: 6           *
       *                                                             *
       * cm_error(%)      p_error(%)      mass_error(%)    *
       *      0.042           0.000             0.000            *
       ***********************************************
       *     Global performance                                 *
       *                                                             *
       *     mass (kg/s):             0.093200                 *
       *     est. choke:              0.107995                  *
       *                        t-t        t-s        s-s          *
       *     eta_p:           0.8453     0.7415                 *
       *     eta_s:           0.8553     0.7583                 *
       *     pr:               0.5800     0.5374    0.6100     *
       *     er (1/pr):      1.7243     1.8609     1.6392    *
       *     power (kW):                   -5.4316              *
       ***********************************************

      A more detailed convergence history is output to the history file, which is described inSpecification of
      Convergence History Data File (*.hst) (p. 117).


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Section 4 : Simulation results on quasi-orthogonal planes and streamlines
   Results are provided at every quasi-orthogonal requested (see control file parameter i_print_plane)
   in the level of detail requested (parameter i_print_level). The data is provided across the span for
   each streamline. If the number of streamlines is greater than 9 then data for every second streamline is
   given. The structure of this data and the information provided varies depending on the type of calculation
   station. The example below is for a radial impeller leading edge:
    Quasi-orthogonal - i = 3
      n_blade n_curve i_type i_row i_spool
        13          6           3     0          0
    Rotor blade - leading edge
    At throat (or just upstream of throat)
    Compressor
    Radial impeller
    Throat area =        0.00274713
    Annulus choke parameters: dm_dcm = 0.79601 Mach_eff = 0.45166
    choke mass at this q_o                    =        7.72100
    choke_mass of machine                    =        7.72100
    choke_mass of this blade row            =        7.72100
    current_mass at this q_o                 =        6.70000
    inlet mass flow                            =        6.70000
    Factor on slope of ree: grad_re = 1.00000               cm_guess_save = 152.57564
    Flow parameters - print_level=1
    streamline        1          3        5             7           9       11       13        15        17
    r [m]         0.07612 0.08753 0.09759 0.10647 0.11445 0.12176 0.12855 0.13493 0.14100
    z [m]       -0.13500-0.13500-0.13500-0.13500-0.13500-0.13500-0.13500-0.13500-0.13500
    1/rc[1/m]     -5.996      1.353   2.758        2.818      2.475    1.984    1.438    0.864    0.244
    throat mm       23.00      24.41  25.66        26.77      27.40    27.84    28.17    28.30    29.00
    f_sl [-]     0.17503 0.17777 0.18110 0.18431 0.18734 0.19021 0.19295 0.19556 0.19806
    f_qo [-]     0.00000 0.17593 0.33098 0.46775 0.59076 0.70340 0.80807 0.90652 1.00000
    f_bl [-]     0.00000 0.00000 0.00000 0.00000 0.00000 0.00000 0.00000 0.00000 0.00000
    f_thr [-] 0.02584 0.03400 0.04157 0.04823 0.05408 0.05923 0.06379 0.06785 0.07150
    gamma_in    1.00000 1.00000 1.00000 1.00000 1.00000 1.00000 1.00000 1.00000 1.00000
    gamma_out 0.00000 0.00000 0.00000 0.00000 0.00000 0.00000 0.00000 0.00000 0.00000
    cm [m/s]       146.87 142.25 145.30 149.18 152.57 155.22 157.11 158.32 158.87
    - error % 0.0001 -0.0002 0.0001 0.0001 0.0001 0.0001 0.0000 -0.0002 -0.0001
    - max           169.57 166.48 168.30 172.19 174.87 177.33 179.61 180.96 186.11
    cu [m/s]           0.00      0.00    0.00          0.00       0.00     0.00     0.00     0.00      0.00
    M_cm [-]         0.437     0.423   0.432        0.444      0.455    0.463    0.469    0.472    0.474
    M_crit[-]       1.000     1.000   1.000        1.000      1.000    1.000    1.000    1.000    1.000
    M_rel [-]       0.765      0.837  0.914        0.985      1.050    1.109    1.163    1.213    1.260
    beta_fl°      -55.19 -59.65 -61.79 -63.21 -64.34 -65.33 -66.23 -67.08 -67.90
    beta_bl°      -43.03 -46.77 -50.17 -52.99 -55.37 -57.46 -59.30 -60.92 -62.35
    incidence       12.16     12.88   11.62        10.22        8.98     7.86     6.93     6.16      5.55
    p [bar]        0.8706 0.8778 0.8730 0.8669 0.8614 0.8571 0.8540 0.8519 0.8510
    t [K]           282.38 283.04 282.60 282.04 281.54 281.14 280.84 280.66 280.57
    rho[kg/m3] 1.0742 1.0806 1.0764 1.0710 1.0661 1.0623 1.0595 1.0577 1.0569
    A*/A            0.9485 0.9758 0.9935 0.9998 0.9980 0.9907 0.9799 0.9666 0.9517
    m/m_max        0.8661 0.8545 0.8633 0.8664 0.8725 0.8753 0.8747 0.8749 0.8536
    m_prime          75.46     84.55   95.91 106.88 116.97 126.15 134.46 141.98 148.76
    m_pr_max        87.12      98.94 111.09 123.37 134.07 144.11 153.70 162.27 174.26
    ch_ratio      0.8662 0.8545 0.8634 0.8664 0.8725 0.8753 0.8748 0.8749 0.8537
    Flow parameters - print_level=2
    eps    [°]       12.82     14.30   12.54        10.34        8.13     6.01     4.00     2.08      0.23
    psi    [°]       77.18     75.70   77.46        79.66      81.87    83.99    86.00    87.92    89.77
    c    [m/s]     146.87 142.25 145.30 149.18 152.57 155.22 157.11 158.32 158.87
    w    [m/s]     257.28 281.50 307.34 330.98 352.35 371.83 389.80 406.55 422.31
    u    [m/s]     211.24 242.91 270.83 295.46 317.60 337.88 356.73 374.45 391.29
    wu [m/s] -211.24 -242.91 -270.83 -295.46 -317.60 -337.88 -356.73 -374.45 -391.29
    M_abs [-]       0.437      0.423  0.432        0.444      0.455    0.463    0.469    0.472    0.474
    alpha_fl°         0.00       0.00   0.00          0.00       0.00     0.00     0.00     0.00      0.00
    pt [bar]       0.9921 0.9921 0.9921 0.9921 0.9921 0.9921 0.9921 0.9921 0.9921
    tt      [K]    293.00 293.00 293.00 293.00 293.00 293.00 293.00 293.00 293.00
    s [J/kgK]         2.29       2.29   2.29          2.29       2.29     2.29     2.29     2.29      2.29
    ds[J/kgK]         0.00       0.00   0.00          0.00       0.00     0.00     0.00     0.00      0.00
    ewb    [-]     0.0500 0.0500 0.0500 0.0500 0.0500 0.0500 0.0500 0.0500 0.0500
    Loading parameters - print_level=3
    w_s [m/s] 287.34 314.82 342.24 366.60 388.17 407.50 425.12 441.51 456.87
    w_p [m/s] 227.21 248.18 272.45 295.36 316.53 336.16 354.47 371.59 387.74
    M_ws     [-] 0.855         0.936   1.018        1.091      1.157    1.215    1.268    1.318    1.364


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      M_wp   [-]   0.676        0.738          0.810          0.879         0.943          1.002         1.058          1.109       1.157
      C_btob [-]   0.234        0.237          0.227          0.215         0.203          0.192         0.181          0.172       0.164


Specification of the Text Data Files (*.txt)
The text data files include lines of text in ASCII format which are intended as input for various software
packages for producing plots of the converged results. The text files can be used as input data for Tecplot.
Standard layout (.lay) files for Tecplot have been prepared which allow typical diagrams to be produced
on the basis of this data. The information is structured in such a way that it can just as easily be used by
Excel or some other similar program with an appropriate interface.

In fact, after running the program, several standard .txt files for Tecplot are produced: one covering the
whole flow field and one for each blade row. The flow field data is written in the file prefix.txt, and the
blade-row data in the files row_01_prefix.txt, row_02_prefix.txt, and so on, whereby the number
of the files refers to the blade rows numbered from the start of the computational domain. You only need
to provide the name of one of these files in the vista_tf.fil file, because the others are automatically
generated and numbered by the program.

Some standard Tecplot layout files have been prepared that operate on the .txt files to produce typical
plots that are needed during the design of a component. For example, the files used for radial compressor
impellers are called: flowfield_2d_v_2_0.lay and rc_impeller_row1.lay. The first of these
prepares a plot showing the 2D meridional channel with contours of constant parameters (such as meridi-
onal velocity, swirl velocity, static temperature, Mach number, cm_error and so on) and the second prepares
blade loading plots for a typical blade row. The layout file (.lay) determines the format of the plot and
the ASCII .txt file contains the data to be plotted. The format and the scales can also be changed on-line
within Tecplot by clicking on the screen. Other Layout files for other cases (ac = axial compressor, hp = hy-
draulic pump, ht= hydraulic turbine, rt = radial turbine, at= axial turbine) are also available and these can
be easily customized (scales, parameters and so on).

The standard Tecplot layout files (.lay) have all been written to work on the data in text files named im-
peller.txt and row_01_impeller.txt, and so on. The first dataset, impeller.txt, contains in-
formation for the contour plots showing the meridional velocity and other parameters projected on the
meridional plane and the second, row_01_impeller.txt, contains the various blade loading parameters
for an individual blade row. If the case concerned has several blade rows then there is also a file called
row_02_impeller.txt, row_03_impeller.txt, and so on; there is one file for each blade row. A
new layout file is needed for each blade row. The letters “impeller” in this name rely on the fact that the
prefix for the .txt file has this name in the vista_tf.fil file.

Other prefixes will produce .txt files containing the prefix as specified in the vista_tf.fil file. In this
case, the layout files need to be modified; the layout files can be opened in a text editor; the name of the
.txt file is on the second line. This name can then be changed to match the name given as a prefix in the
vista_tf.fil file. Alternatively, the same layout files can be used for several cases if all data that needs
to be plotted always retains the prefix name impeller; the text output file from vista_tf always has
the name impeller.txt in the vista_tf.fil file.

Generally, a good strategy is to set up the .aero, .cor, .con, and .txt files with a certain prefix in the
vista_tf file and to let these keep the same names for all runs on a particular case because they normally
do not change as the design progresses. It then remains necessary to switch the .geo files around to look
at different impellers, or else the prefix for the .geo file can be retained and the cases can be distinguished
by simply putting them into different directories to distinguish the different cases.

The data in the prefix.txt file is in approximately the following format:
 TITLE
 Flow field data for whole flow field from hub to shroud for all q-os

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                                                                                                               Screen Output Files (screen.scn)


Variables = '"r" "z" "cm" "cu" "cr" "cz" "p" "t" "pt" "tt" "s" "h" "q_o" "error" "choke_ratio"
"M_rel" "M_abs" "alpha_flow" "beta_flow" "1/rc" "beta"'

"r"                  Radius coordinate
"z"                  Axial coordinate
"cm"                 Meridional velocity
"cu"                 Swirl velocity
"cr"                 Radial velocity
"cz"                 Axial velocity
"p"                  Static pressure
"t"                  Static temperature
"pt"                 Total pressure
"tt"                 Total temperature
"s"                  Entropy
"h"                  Static enthalpy
“q_o”                an integer identifying the particular type of q-o
“error”              Meridional velocity error in %
"choke_ratio"        choke ratio (ratio of local mass flow to choke flow at this location)
"M_rel"              Relative Mach number
"M_abs"              Absolute Mach number
"alpha_flow"         Absolute flow angle [°]
"beta_flow"          Relative flow angle [°]
"1/rc"               Curvature ( inverse of the radium of curvature)
"beta”               Blade angle [°]

The data in the row_01_prefix.txt file is approximately in the following format:
TITLE
Data on hub, mean and tip streamlines for all blade rows from LE to TE
and data along leading edge and trailing edge of all blade rows

VARIABLES =VARIABLES = "i_type", "f_bl", "M", "M_s", "M_p", "w", "w_s", "w_p",...
"p", "p_s", "p_p", "c_btob", "c_htos", "beta_bl", "beta_fl", "dep_angle", "gamma_in", ...
gamma_out", "f_qo", "de_haller", "cp_ideal", "incidence", "deviation", "lambda", ...
"df_lieblein", "zweifel" "c_lift", "c_zw"
"f_bl"               Fraction of meridional distance along the blade
"M"                  Mean mid-passage Mach number (relative to blade)
"M_s"                Suction side Mach number
"M_p"                Pressure side Mach number
"w"                  Mean mid-passage velocity (relative to blade)
"w_s"                Suction surface velocity
"w_p"                Pressure surface velocity
"p"                  Static pressure in mid-channel between two blades
"p_s"                Suction surface static pressure
"p_p"                Pressure surface static pressure
"c_btob"             Blade to blade loading parameter
                     (c_btob = (w_s-w_p)/w, that is the difference between suction surface
                     and pressure surface velocities divided by the mid-channel velocity
"c_htos"             Hub to shroud loading parameter
                     (c_htos = (cm_shroud – cm_hub)/ cm_mean, that is the difference
                     between the meridional velocity on the casing and the hub divided by
                     the mean velocity.
"beta_bl"            Blade angle in degrees [°]
"beta_fl"            Flow angle in degrees [°]
"dep_angle"          Departure angle in degrees [°]
"gamma_in"           Blending functon at blade inlet
"gamma_out"          Blending function at blade outlet
"f_qo"               fractional distance along q-o
"de_haller"          De Haller number
                     (de_haller = w2/w1, that is outlet/ inlet relative velocity
"cp_ideal"           Ideal static pressure recovery coefficient
                     ( Cpideal = 1 – (de_haller)**2 )
"incidence"          Incidence at the leading edge [°]
"deviation"          Deviation at the trailing edge[°]
"lambda"             Work coefficient ( lambda = (h2-h1)/u**2, that is Deltah / u squared)
"df_lieblein"        Lieblein Diffusion Factor (see below)
"zweifel"            Zweifel loading parameter (see below)
"c_lift"             Lift coefficient (see below)
"c_zw"               Lift coefficient times solidity (see below)




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Note that the values of the last four parameters have been included mainly for axial blade rows. Each of
them includes the blade solidity (ratio of chord to spacing) in its definition. In radial machines, the spacing
and solidity change with radius along the streamline. There is no generally agreed method to calculate these
parameters for radial machines, so the mean value of the spacing has been selected in the following definitions
used in Vista TF. In any case, caution is suggested in the use of these parameters for radial machine blade
rows because the experimental basis for limit values has generally been derived from axial machines.

Lieblein diffusion factor (df_lieblein)




Zweifel coefficient (zw)




Lift coefficient (CL)




where

Zwiefel number (c_zw)




Specification of the CFD-Post Output Files (*.csv)
The text data files *prefix.csv include lines of text in ASCII Comma Separated Variable format files (.csv)
which are intended as input for CFD-Post for plotting purposes, using the user surface data format. For details
of this format, see the documentation provided with CFD-Post.

In the current .csv files, the following data is available for each grid node:
 [Name]
 Vista-TF
 [Data]
 X [m], Y [m], Z [m], Cm [m/s], Cu [m/s], Cr [m/s], Cz [m/s], p [bar], t [K], s [J kg^-1 K^-1],
 h [J/kg], q_o [], error [], M_rel[], M_abs[], rc [m^-1]

The file global_prefix.csv contains a list of parameters, whereby these are specified as:
 Name 1 = value1 [units]
 Name 2 = value2 [units]

                                              .
Separated by comment lines which begin with “#”

In addition, there are four additional files produced for each blade row from 1 to n:
 row_0n_hub_prefix.csv
 row_0n_mean_prefix.csv
 row_0n_tip_prefix.csv
 row_0n_loading_prefix.csv

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                                                                                                                  Screen Output Files (screen.scn)

These contain essentially similar information to the row_0n_prefix.txt files described above, but this
is split into four separate files: one for the hub, one for the mean span, one for the tip, and one for the
loading parameters.

Specification of Convergence History Data File (*.hst)
The convergence history data file includes lines of text in ASCII format that show the convergence of the
simulation. This contains details of the convergence of the main iterative procedures, and extensive details
of the terms in the radial equilibrium equation for each stream tube and calculating plane. It is rare for this
to be examined in any depth, but this can be useful to identify problems if the solution fails to converge.

Section1: Input Data
   At the start of the .hst file, the input data is recorded. This is essentially in the same format as the input
   files. At the start of this file, there is a list of the names of the input data files that were used. This inform-
   ation can be useful if an error occurs in the input data because the .hst file records only the data that
   has been successfully read into the program.
Section 2: Convergence Data
   At every iteration, a summary of the iteration progress is provided. It looks like this:
     History of the main iteration loop
     ----------------------------------
          it_main: 1 error_cm(%): 100.000 at i_qo: 0 j_sl: 0 it_mass: 11 at i_qo: 1
          it_main: 2 error_cm(%): 38.940 at i_qo:10 j_sl:17 it_mass: 11 at i_qo: 1
          it_main: 3 error_cm(%): 30.036 at i_qo:10 j_sl:17 it_mass: 11 at i_qo: 3
          it_main: 4 error_cm(%): 24.600 at i_qo:10 j_sl:17 it_mass: 11 at i_qo: 4
          it_main: 5 error_cm(%): 20.939 at i_qo:10 j_sl:17 it_mass: 11 at i_qo: 5
          it_main: 6 error_cm(%): 18.306 at i_qo:10 j_sl:17 it_mass: 11 at i_qo: 6
          it_main: 7 error_cm(%): 16.403 at i_qo:10 j_sl:17 it_mass: 11 at i_qo: 6

     .....

          it_main:   284   error_cm(%):          0.013     at    i_qo:     7   j_sl:17       it_mass:        1   at   i_qo:      1
          it_main:   285   error_cm(%):          0.012     at    i_qo:     7   j_sl:17       it_mass:        1   at   i_qo:      1
          it_main:   286   error_cm(%):          0.011     at    i_qo:     7   j_sl:17       it_mass:        1   at   i_qo:      1
          it_main:   287   error_cm(%):          0.010     at    i_qo:     7   j_sl:17       it_mass:        1   at   i_qo:      1
          it_main:   288   error_cm(%):          0.009     at    i_qo:     7   j_sl:17       it_mass:        1   at   i_qo:      1

Section 3: Streamline Curvature Solution Data
   At every quasi-orthogonal, details of the terms in the radial equilibrium equation for each stream tube
   are provided. This can be useful in identifying errors and also helpful to determine the magnitude of
   the terms in the equations. “rhs” is the value of the right hand side of the radial equilibrium equation,
   giving the square of the gradient of the meridional velocity.

    The streamline curvature solution data looks like this:
     Quasi-othogonal - i = 5
      n_blade n_curve i_type i_row i_spool
          9        8          3         0     0
     Radial equilibrium parameters -print_level = 4
     rhs            1049.90 1059.86 871.10 684.48 510.68 349.39 199.63               55.28
     ret                 0.00      0.00     0.00     0.00     0.00     0.00     0.00      0.00
     ret_dh             0.00      0.00     0.00     0.00     0.00     0.00     0.00      0.00
     ret_tds            0.00      0.00     0.00     0.00     0.00     0.00     0.00     0.00
     ret_drcu          0.00       0.00     0.00     0.00     0.00     0.00     0.00     0.00
     sct            1049.90 1059.86 871.10 684.48 510.68 349.39 199.63               55.28
     sct_rc          641.48 681.97 558.43 431.70 315.91 211.42 118.25                34.87
     sct_dcm         408.43 377.89 312.67 252.78 194.78 137.97              81.38    20.40
     bft                 0.00      0.00     0.00     0.00     0.00     0.00     0.00      0.00
     dft                 0.00      0.00     0.00     0.00     0.00     0.00     0.00      0.00
     cm_error%     -0.0010 0.0002 -0.0003 -0.0007 -0.0007 -0.0003 0.0003 0.0010
     f_mixing        0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000
     1/rc        2.853     4.466     4.153    3.505    2.773    2.016    1.261    0.517 -0.209
     cm        137.936 145.590 152.396 157.708 161.716 164.594 166.473 167.450 167.568
     rcu         0.000      0.000    0.000    0.000    0.000    0.000    0.000    0.000    0.000

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      drcu/dm       47.323 53.336 48.562 35.419 15.376 -11.226 -43.868 -81.313-123.649
      s               1.885  1.885   1.885  1.885  1.885   1.885    1.885   1.885   1.885
      bl_block       0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000


Software Limitations
There are several potential sources of errors and uncertainties in all CFD simulations, all of which are extremely
relevant in turbomachinery applications using a throughflow program, such as Vista TF. The standard cat-
egorization of such errors is into the following groups:

 •    Numerical errors
 •    Model errors
 •    Application uncertainties
 •    User errors
 •    Software errors

and these are briefly described next.

Numerical errors decrease the quality of simulations and can be reduced but not eliminated. The control of
numerical error is largely a matter of adequate grid design, appropriate numerical discretization, and adequate
level of convergence. An example in Vista TF is the approximation of the streamlines by a piecewise parabola
through 3 points. In a throughflow calculation the so-called model errors probably outweigh all other sources
of error. These are related to the fact that the equations that are solved do not really describe the real flow
particularly adequately (in this case the solution is for inviscid, circumferentially-averaged mean values on
widely spaced grid lines). Application uncertainties may be only partly in your control and are related to the
detail with which aspects of the geometry are accurately known or specified. Typical examples would be a
lack of knowledge about the fillet radii in the geometry for a blade row calculation, or not having correct
information about the inlet boundary conditions for a specific calculation. User errors relate to incorrect use
of the program, such as making use of incorrect control parameters to control the calculation. With regard
to software errors, every reasonable precaution to ensure the accuracy and reliability of the Vista TF program
has been taken. However, when using the program, especially for a critical design, you should first complete
an appropriate validation and calibration process. A good turbomachinery analysis procedure dictates that
any program, including Vista TF, must be thoroughly tested with non-critical data before there is any reliance
on it.

Streamline Curvature Throughflow Theory
Vista TF is a general purpose streamline curvature throughflow program for the analysis of all types of tur-
bomachinery, but with special emphasis on single stage centrifugal machines, such as radial pumps, turbines,
and compressors, which can usually not be calculated by other throughflow programs.

The program has the ability to compute radial blade rows in both compressors and turbines, and the swirling
flows in the radial channels of such machines. This is possible because the blade and channel geometry is
defined in a very general way independent of the meridional streamline direction.

This section of the documentation is intended for readers who are not familiar with throughflow methods;
it provides a general introduction to the streamline curvature axisymmetric meridional throughflow calculation
method. Some details are given in Casey and Robinson (2008) [5] (p. 125). This section includes a list of
technical papers on the subject.

The following topics are discussed:
 The Equations
 The Mean Stream Surface

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 The Grid
 Ductflow and Throughflow
 Iterative Solution Procedure
 Initial Estimate
 Radial Equilibrium Equation
 Combination of Velocity Gradient and Continuity Equations
 Relaxation Factors
 Streamline curvature
 Equations for Enthalpy and Angular Momentum
 Boundary Conditions
 Empirical Data
 Blade-to-blade Solution
 Spanwise Mixing
 Streamline Curvature Throughflow Theory: Bibliography

The Equations
The equations that are solved are:

 •   The continuity equation
 •   The energy equation (Euler equation of turbomachinery)
 •   A suitable equation of state
 •   The inviscid momentum equation for the flow on the mean axisymmetric stream surface

Although these equations are inviscid and do not include frictional forces, the effect of the losses are included
by empirical changes to the entropy in the equation of state, such that the final solution has a density and
pressure field consistent with the presence of losses in the flow.

The Mean Stream Surface
This blade-like surface may be regarded as being obtained by averaging all flow properties in the circumfer-
ential direction, or as being the flow on a mean stream surface between the blade rows, whose orientation
is roughly determined by the blade camber surface. The flow blockage caused by the blades is roughly fixed
by the circumferential blade thickness of the blades. It is often known as the S2 meridional stream surface,
in contrast to the S1 blade-to-blade surface, and in fact corresponds to the so-called S2m surface in the
theory of Wu (1952) [22] (p. 126). See Figure : S1 and S2 Stream Surfaces in the Theory of Wu (1952) (p. 120).
Note that it has an arbitrary orientation in the circumferential direction and that the flow in the mean stream
surface is determined by the slope angles of the surface to the axial and the radial directions, both of which
need to be specified in the geometrical input data.




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Figure: S1 and S2 Stream Surfaces in the Theory of Wu (1952)




The Grid
The grid for the calculation is based on the streamlines of the mean circumferentially averaged flow in the
meridional direction, and fixed calculating stations which are roughly normal to the streamlines. The meridi-
onal streamline grid is not fixed, apart from the hub and shroud streamlines on the annulus walls, but
changes continually during the iterations so that location of the final streamlines is a result of the solution
The fixed calculating stations are orientated with the blade row leading and trailing edges and are often
known as quasi-orthogonals because they are normally nearly orthogonal to the streamlines. The quasi-or-
thogonals can be in duct regions, that is in the blade-free space upstream and downstream of blade rows,
at the leading and trailing edges of the blade rows (which actually are also generally considered to be in
the duct region) and internally within the blade rows. See Figure : Quasi-orthogonal Calculating Stations in
an Axial Compressor Stage Calculation (p. 121). The computational results are available only at the points
where the streamlines cross the quasi-orthogonals. In comparison with modern CFD methods, a very crude
grid is used with typically 9 to 17 streamlines and 3 to 15 quasi-orthogonals per blade row, giving 50 to 300
nodes per blade row in comparison to 100 000 to 500 000 in modern CFD simulations.




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Figure: Quasi-orthogonal Calculating Stations in an Axial Compressor Stage Calculation




In many early streamline curvature programs, the quasi-orthogonals were generally straight radial lines from
hub to casing placed roughly at the location of the leading and trailing edges, but given the more extensive
use of lean and sweep in modern designs, and the natural leading edge and trailing edge curvature arising
from the variable stagger across the span in most rotors, curved quasi-orthogonals of arbitrary orientation
are more appropriate. The use of a grid involving meridional streamlines, all of which proceed smoothly
from the inlet plane to the outlet plane of the calculation domain, assumes that there is no reverse flow,
and thus operation points with reverse flow in the mean meridional flow (even at the design point) cannot
be calculated by this method.

Ductflow and Throughflow
Earlier methods, which did not include blade internal calculating planes, are often known as duct flow
methods because only planes in the duct regions between the blades, and at the leading and trailing edges,
are used. Throughflow refers to methods in which internal planes within each blade row are included as
shown in Figure : Quasi-orthogonal Calculating Stations in an Axial Compressor Stage Calculation (p. 121). In
throughflow methods, the component of the blade force acting along the direction of the quasi-orthogonal
can be included in the meridional throughflow equations, so that some global aspects of the effect of the
blade lean on the meridional flow can be included. This is not possible in duct flow methods without some
empirical adjustment of the pressure gradients.

Iterative Solution Procedure
The solution method is iterative in terms of several variables (primarily the meridional velocity, but also the
density, streamline location, and other variables), all of which progressively converge to a final converged
solution within a fairly complex structure of three nested iterations. In this convergence procedure, many
variables lag behind the main iteration for changes in the meridional velocity, so that during one iteration
leading to an update of the meridional velocity, many parameters are treated as constant and are then up-
dated based on the new estimate of the meridional velocity prior to the next iteration. It is assumed that
this has no effect on the solution provided that a converged solution for all variables is reached.

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Initial Estimate
The initial solution generally comprises a first guess of streamline positions (typically by dividing the flow
path into equal areas at each quasi-orthogonal) and flow variables at all the grid points (that is, the junction
points between the variable streamlines and the fixed quasi-orthogonals). This is then successively refined
as a result of each iteration. Once a first estimate of the streamline positions is in place then various terms
in the radial equilibrium equation, such as the curvature of the streamlines or the rate of change of meridi-
onal velocity along the streamlines, can be determined.

Radial Equilibrium Equation
The momentum equation on the mean stream surface is a form of the radial equilibrium equation, giving
a velocity gradient equation for the gradient of the meridional velocity along a calculating station, or quasi-
orthogonal:




This equation is given in many text books (see Cumpsty (1989) [6] (p. 125)) and is not repeated here. It relates
the velocity gradient to the shape and the current positions of the streamlines, to the orientation of the
mean stream surface, and to the flow parameters and their gradients from the previous iteration. In its
simplest form, this equation is the well-known simple radial equilibrium equation of turbomachinery flows,
which gives the relationship between the radial gradient of the axial velocity and the gradient of the swirl
in the radial direction, as follows:




In its general form the radial equilibrium equation takes into account flow gradients, streamline curvature,
and radial flows, and allows a general arbitrary orientation of the quasi-orthogonal lines. The key difference
between the simple radial equilibrium equation and the more general equation is the inclusion of the
streamline curvature terms, and it is these terms that give their name to the method. There are several forms
of this velocity gradient equation, but the one used here follows the method of Denton (1978) [7] (p. 125),
but takes into account the blade force terms as described in chapter 3.4 of the book by Cumpsty (1989)
[6] (p. 125).

Combination of Velocity Gradient and Continuity Equations
The velocity gradient equation is solved in combination with a method for finding the correct velocity level
on the mean streamline that ensures that the velocity along the quasi-orthogonal satisfies the continuity
equation giving the correct mass flow across the quasi-orthogonal. See Figure : Continuity and the Velocity
Gradient Used in Determining the Meridional Velocity Level (p. 123). The meridional velocity on the mean
streamline is specified in the innermost iteration, integrated across the flow channel with the help of the
meridional velocity gradient, and then continually updated until the mass flow is correct. This requires some
care to ensure that the method converges for all mass flows up to the choking mass flow. In this iteration,
the density is also needed in the continuity equation. In fact there are two values of the density that can
be used, corresponding to supersonic or subsonic flow. In this method, no attempt is made to distinguish
these during the innermost iteration; the density is simply taken as constant at the value from the previous
iteration, and automatically takes on the supersonic or subsonic value as the iteration converges.




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                                                                                                Streamline Curvature Throughflow Theory

Figure: Continuity and the Velocity Gradient Used in Determining the Meridional Velocity
Level




Relaxation Factors
The meridional velocity distribution along the quasi-orthogonal determines the spacing of the streamlines
of the meridional flow, and hence the meridional streamline positions. These positions are continually updated
as the program converges. Generally, it is not acceptable to use the newly calculated positions of the
streamlines directly from one iteration to the next, but a damping factor (often much less than unity) is re-
quired to factor the streamline shifts to obtain convergence. A big weakness of streamline curvature methods
is that the required damping factor becomes very small when the quasi-orthogonal lines are closely spaced,
and so improved accuracy through more calculating planes causes a large increase in calculating time. For
this reason, a relatively coarse grid (compared to CFD computations) is used, leading to calculations that
take just a few seconds on a modern PC. The problem with closely spaced quasi-orthogonals is related to
the large errors in the estimated streamline curvature when a small error in the streamline position is present.
It is for this reason that many methods do not include blade internal calculation stations because these
automatically decrease the spacing between adjacent quasi-orthogonals.

Streamline curvature
The streamline positions can be used to interpolate new blade element data appropriate to their current
location and to find the slopes, curvatures, and derivatives of the flow parameters along the streamlines.
This data is needed in the radial equilibrium equation (velocity gradient equation; see Radial Equilibrium
Equation (p. 122)). The accuracy and stability of streamline curvature methods is related to the prediction of
the curvatures of the streamlines. Several different numerical methods for this have been examined. In the
current method, the curvatures are calculated with a parabolic approximation through three adjacent points
along the streamline.

Equations for Enthalpy and Angular Momentum
In the region between blade rows, the total enthalpy and angular momentum may be considered to be
convected along the meridional streamlines from the previous station. The entropy is also convected but
rises due to the additional losses between the calculating stations. In a blade row, the changes in momentum
and enthalpy are calculated from the Euler equation on the assumption that the flow follows the mean
stream surface. The mean blade stream surface is roughly orientated in alignment with the camber surface
of the blade, but methods are needed for finding the true fluid flow direction taking into account the incidence
and deviation of the flow from the mean blade surface. This is generally dealt with using empirical correlations
for outlet angle, deviation, or slip factor.

Boundary Conditions
At the inlet plane (first quasi-orthogonal) you are generally required to specify the variation of total pressure,
total temperature, and angular momentum or flow angle, together with the gas data and information on

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the mass flow at the outlet plane. For calculations with choked flows, it is not possible to calculate with the
mass flow, making it necessary to calculate with specified outlet static pressure, such that the mass flow is
a result of the simulation.

Empirical Data
Additional empirical methods are used to provide data for the loss production, for the boundary layer
blockage, and for the deviation of the flow direction from the mean blade camber surface, so that the effect
of viscosity can be taken into account. In fact Denton (1978) [7] (p. 125) argues that “in many applications,
throughflow calculations are little more than vehicles for inclusion of empiricism in the form of loss, deviation
and blockage correlations, and their accuracy is determined by the accuracy of the correlations rather than
              .
the numerics” The three main effects of the empirical data are:

 •    In the equation of state, a change in the entropy leads to a pressure loss for a given value of the total
      enthalpy.
 •    In the continuity equation, the blockage due to the boundary layer displacement effect leads to a
      higher value of the meridional velocity.
 •    In the momentum equation, the deviation of the flow from the blade direction leads to a change in the
      calculated swirl velocity.

Thus, although the basic inviscid equation of motion used by the method is inherently incapable of predicting
entropy rises through the machine, some effects of losses can be included. There are numerous possible
combinations of data for the empirical information, based on various definitions of loss coefficients, dissipation
coefficients, efficiencies, and so on, and this leads to the largest source of confusion in the data preparation
for throughflow programs, and a large and complex array of branching “IF” statements within a typical
throughflow program to deal with the alternatives. In making this program, a single form of loss definition
has been included based on the entropy rise.

Blade-to-blade Solution
The mean stream surface provides the flow field in the meridional plane through the turbomachine. Generally
the engineer also needs information on the blade surface velocity and Mach number distributions, so the
meridional solution needs to be combined with a blade-to-blade method to find blade surface velocities.
This may be either a simple approximation or a more accurate solution of the blade-to-blade flow equations.
The more accurate methods enable the exact location of the mean stream surface of the flow to be determined
at different blade-to-blade planes, so this can also lead to a further iteration in which the mean stream surface
is no longer considered as fixed. Such iterative solutions are often known as S1/S2 solutions (the S1 surface
being the blade-to-blade surface and the S2 surface being the meridional surface. See Figure : S1 and S2
Stream Surfaces in the Theory of Wu (1952) (p. 120)). This technique has generally been replaced these days
by fully 3D CFD solutions with mixing planes, but is still of historical interest. The simpler methods generally
use a linear approximation for the velocity variation from suction surface to pressure surface. These can be
expected to produce sensible results only when a sufficient number of internal blade row calculating stations
are included in the grid, probably 5 as the minimum.

Spanwise Mixing
A major shortcoming of the basic streamline curvature method is the neglect of the spanwise transport of
angular momentum, energy, and losses in the direction normal to the streamlines. By definition, a
throughflow program is based on the assumption that the flow remains in concentric streamtubes as it
passes through the turbomachine, and no mass transfer occurs across the meridional streamlines which are
the streamtube boundaries. In a duct region of a throughflow calculation, enthalpy, angular momentum
(swirl), and entropy are taken to be conserved along the meridional streamlines. In reality, there are several


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mechanisms that lead to an apparent spanwise transport of fluid relative to flow on the mean streamlines,
as follows:

 •   Non-axisymmetric blade-to-blade stream surfaces as a result of streamwise vorticity being shed by the
     blades (stream-surface twist)
 •   Secondary flows in the end-wall boundary layers and in the blade boundary layers
 •   Wake momentum transport downstream of blade rows
 •   Tip clearance flows with tip clearance vortices
 •   Turbulent diffusion

As a result of not modeling these effects, throughflow programs in which realistic loss levels are specified
for the end-wall regions often predict unrealistic profiles of the loss distribution after several stages because
there is no mechanism for the high losses generated near the end walls to be mixed out. The simplest ap-
proach to deal with this problem is to specify unrealistic loss distributions across the span that avoid high
levels in the end walls. In fact, in preliminary design calculations, this is often adequate. A useful approxim-
ation is to specify a mean-line value of loss coefficient or efficiency and to assume that the entropy generated
by the losses is the same on each stream-tube. This approximates a complete mixing of the entropy distri-
bution across the span.

Several more sophisticated methods to include more detailed physics of these mixing processes have been
attempted so that realistic loss distributions can be specified. The common approach is to model the spanwise
mixing as turbulent diffusion, even though some of the effects are due to deterministic flow features. Even
with throughflow programs in which spanwise mixing is incorporated, it is still generally not possible to
fully incorporate the very high loss levels close to the end walls. Vista TF includes these effects as turbulent
diffusion across the streamlines.

Streamline Curvature Throughflow Theory: Bibliography

[1] G. G. Adkins and L. H. Smith. “Spanwise mixing in axial flow turbomachines”. Trans ASME Journal of Engin-
         eering for Power , Vol. 104. pg. 97-110. 1982.

[2] P. M. Came. “Streamline curvature throughflow analysis”. Proc. First European Turbomachinery Conference,
         VDI Berichte 1185. pg. 291. 1995.

[3] M. V. Casey and O. Hugentobler. “The prediction of the performance of an axial compressor stage with
         variable stagger stator vanes”. VDI Berichte Nr. 706. pg. 213-227. 1988.

[4] M. V. Casey and P. Roth. “A streamline curvature throughflow method for radial turbocompressors”. I. Mech.
         E. Conference C57/84. 1984.

[5] M. V. Casey and C. J. Robinson. “A new streamline curvature throughflow code for radial turbomachinery”.
         ASME TURBOEXPO 2008, ASME GT2008-50187. Berlin. 2008.

[6] N. A. Cumpsty. Compressor aerodynamics. Longman Scientific. New York. 1989.

[7] J. D. Denton. “Throughflow calculations for axial flow turbines”. Trans ASME, Journal of Engineering for Power,
          Vol 100. 1978.

[8] J. D. Denton and C. Hirsch. “Throughflow calculations in axial tubomachines”. AGARD Advisory Report No.
          175 AGARD-AR-175. 1981.




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[9] S. J. Gallimore. “Spanwise mixing in multistage axial flow compressors: part II throughflow calculations including
          mixing”. Trans. ASME, Journal of turbomachinery, Vol. 108. pg. 10-16. 1986.

[10] I. K. Jennions and P. Stow. “The quasi-three-dimensional turbomachinery blade design system, Part I:
          Throughflow analysis, Part II: Computerized system”. Transactions of the ASME, Journal of Engineering
          for Gas Turbines and Power Vol. 107. pg. 308-16. 1985.

[11] I. K. Jennions and P. Stow. “The importance of circumferential non-uniformities in a passage averaged quasi-
          three-dimensional turbomachinery design system”. Transactions of the ASME, Journal of Engineering for
          Gas Turbines and Power Vol. 108. pg. 240-5. 1986.

[12] K. I. Lewis. “Spanwise transport in axial-flow turbines: Part 2 - Throughflow calculations including spanwise
          mixing”. Trans. ASME, Journal of turbomachinery, Vol. 116. pg. 187-193. 1984.

[13] B. Liu, S. Chen, and H. F. Martin. “A primary variable throughflow code and its application to last stage reverse
         flow in LP steam turbine”. Paper: IJPGC2000-15010, Proc. Int. Joint Power Generation Conference, July
         23-26. Miami Beach, Florida. 2000.

[14] H. Marsh. “A digital computer program for the through-flow fluid mechanics in an arbitrary turbomachine
        using a matrix method”. Aeronautical Research Council R and M 3509. 1968.

[15] C. Hirsch and J. D. Denton. “Throughflow calculations in axial turbomachines”. AGARD Advisory report No.
         175, AGARD-AR-175. 1981.

[16] K. I. Lewis. “Spanwise transport in axial flow turbines: part 2 - throughflow calculations including spanwise
          transport”. Trans. of ASME, Journal of Turbomachinery, Vol. 116. pg. 187-193. 1994.

[17] R. A. Novak. “Streamline curvature computing procedures for fluid flow problems”. Trans. of ASME, Journal
         of Engineering for power, Vol 89. pg. 478-490. 1967.

[18] M. Schobeiri. Turbomachinery Flow Physics and Dynamic Performance. Springer. Berlin. 2005.

[19] L. H. Smith. “The radial equilibrium equation of turbomachinery”. Trans. ASME Journal of Engineering for
         Power, Vol 88. pg. 1-12. 1966.

[20] D. H. Wilkinson. “Streamline curvature methods for calculating the flow in turbomachines”. Report No
        W/M(3F). English Electric. Whetstone, England. pg. 1591. 1969.

[21] D. H. Wilkinson. “Stability, convergence, and accuracy of two-dimensional streamline curvature methods
        using quasi-orthogonals”. paper 35, I.Mech.E. Convention. Glasgow. 1970.

[22] C. H. Wu. “A general theory of three-dimensional flow in subsonic, and supersonic turbomachines of axial,
         radial and mixed-flow types”. Trans. ASME, Nov. 1952. pg. 1363-1380. 1952.

[23] C. C. Yeoh and J. B. Young. “Non-equilibrium throughflow analyses of low-pressure, wet steam turbines”.
         ASME J. Eng. for Gas Turbines & Power, Vol 106. pg. 716-724. 1984.



Appendices
The following appendix topics are available:
 Appendix A: A Note on Sign Convention for Angles and Velocities
 Appendix B: Example of a Control Data File (*.con)
 Appendix C: Example of a Geometry Data File (*.geo) for a Radial Impeller

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 Appendix D: Example of an Aerodynamic Data File (*.aer)
 Appendix E: Examples of Correlations Data Files (*.cor)
 Appendix F: Troubleshooting
 Appendix G: The RTZTtoGEO Program

Appendix A: A Note on Sign Convention for Angles and Velocities
When looking along the axis of the machine in the direction of flow we have a cylindrical coordinate system
(r, theta, z) (or (r, θ , z)) . The angular coordinate (theta) is taken as positive in the clockwise direction and
negative in the anti-clockwise direction. The normal case considered by Vista TF is clockwise rotation when
looking along the axis in the direction of the flow so that the angular coordinate increases in the rotational
direction. See Figure : Coordinate System used by Vista TF (p. 127) below.

Figure: Coordinate System used by Vista TF




The sign convention for velocity values is that an axial velocity component in the positive axial direction is
positive, a radial component in the positive radial direction is positive, and a circumferential component in
the positive angular direction (direction of rotation) is positive.

Blade lean angles are then defined from the axial and radial directions in a similar way using the rotational
direction as a basis. As you move along an axial rotor blade in the axial direction of a clockwise rotating
machine then the blade angle theta steadily decreases as the blade is sloped backwards against the rota-
tional direction (radial impeller outlet angles are generally also backswept). In a stator vane the angular co-
ordinate increases as you step along the blade in the meridional direction. The rate of change of the angular
coordinate with the meridional direction then defines the sign of the blade angle, and this applies for the
blade angles, flow angles and also applies to the blade lean angles. See below.

For example, in an axial compressor rotor where the blades lean back from the direction of rotation, theta
becomes more negative as you move along the blade from the leading edge (LE) to the trailing edge (TE).
In a compressor stator, theta becomes more positive as you move along the blade. This rule works for axial,
radial, and mixed flow compressors, provided the meridional direction is used as a basis. In a turbine stator

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theta also increases positively from LE to TE and, in a turbine rotor, theta decreases from LE to TE. There are
some exceptions to this rule, related to high camber at leading edges to adapt the flow to the incoming
flow direction.

      Note

      Vista TF uses the rules outlined above to identify the type of machine from the geometrical data
      of the blade angles in the geometry input file, so you do not have to specify this.

Definition of Blade Lean Angles
Consider a point q on a radial impeller blade camber surface, as shown in Figure : Definition of Angles (p. 128).
We can define the blade lean angles,     and       as the angle made by the blade fibers with a radial line
and the angle made with an axial line, as follows:




Figure: Definition of Angles




Notes on      :

 •    This is the blade lean to the radial direction.
 •    This angle is zero for a blade comprising purely radial blade elements, so is generally close to zero for
      axial blade rotor rows (which tend to have no lean) and centrifugal impeller leading edges or radial
      turbine trailing edges.
 •    It is non-zero for blades with lean. If, when moving along the blade in the radial direction, the lean is
      against the direction of rotation then it is negative and lean in the direction of rotation is positive.


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 •   A radial compressor impeller with a purely radial blade at impeller outlet (no backsweep) would have
        =0° and        corresponds to the back-sweep angle in a typical back-swept radial impeller. For an
     impeller with 30° of back-sweep,   would be negative (-30°) at the trailing edge. Note that, in some
     sign conventions, the back-sweep angle would be given a positive value, but in Vista TF, it is negative.
 •   In a the diffuser of a radial pump or compressor stage, this angle corresponds to the diffuser blade
     angle and would be typically between 60° and 70° at the leading edge, and would decrease through
     the blade row.

Notes on        :

 •   This is the blade angle measured from the axial direction in the direction of rotation.
 •   In an axial blade element (or close to the leading edge of a typical radial impeller or the trailing edge
     of a radial turbine impeller), this is the blade camber angle. At the inlet to an axial blade row, this is
     the blade inlet angle; at the outlet, it is the blade outlet angle.
 •   In a typical rotor blade, it is negative and, in a typical stator, it is positive. Note that the common excep-
     tions would be turbine rotors with a low degree of reaction and compressor rotor roots with very high
     turning.
 •   In a compressor where the flow is turned by the blade rows towards the axial direction, the absolute
     values decrease from the leading edge to the trailing edge whereas in a turbine where more swirl is
     added to the flow, the absolute values increase from the leading edge to the trailing edge.
 •   For a blade with purely axial blade elements (as in a typical 2D diffuser and at a radial impeller outlet
     with no rake angle), this angle is zero.

Definition of Meridional Streamline Inclination Angle or Pitch Angle

The angle       is the inclination of a meridional streamline to the axial direction:




which on the hub and casing walls becomes the meridional slope angle of the walls.

Definition of Blade Angle

Internally the program uses the angles                      and           to calculate            , which is the effective blade angle measured
from the meridional direction.             is defined as:




Notes on    :

 •   The wrap angle is taken as positive in the direction of rotation. This is consistent with the flow angle
     definition used by the program.

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 •    This angle is zero for a blade in which the wrap angle does not change in the meridional direction, such


      as an axial strut in an axial channel or a radial strut in a radial channel, where                                               .
 •    If the wrap angle increases in the meridional direction then the blade angle is positive. If the wrap angle
      decreases in the meridional direction then the blade angle is negative.
 •    Note that the actual value of the blade angle as seen by the flow is dependent on the lean angle of
      the meridional streamline, and is not an absolute fixed value for a certain blade. Thus a change in the
      meridional direction of the flow at an impeller outlet with lean changes the value of the blade angle.

Appendix B: Example of a Control Data File (*.con)
The following is a described example of a control data file:

Three lines to identify the run (maximum 72 characters per line):
 PCA stage
 Control parameters for typical radial impeller
 5 May 2008

Two lines for the integer control parameters:
 n_sl max_it_main max_it_mass
 9      500           10

Two lines for integer control parameters for output data and the use of the restart file:
 i_print_plane i_print_level i_print_units i_display i_restart i_interface
        4            5             0            0        0          0

Two lines for integer control parameters for various models and reference parameters:
 i_expert i_flow i_fluid i_inbc i_mass i_mix i_ree
     0      1       0       0      0     0     0

Two lines for convergence and damping factors:
 damp_sc damp_vl cm_start tolerance_cm tolerance_mass grad_ree
   0.25    0.25     0.2       0.01         0.005        1.00


Appendix C: Example of a Geometry Data File (*.geo) for a Radial Impeller
The following is a described example of a geometry data file:

Three lines to identify the run:
 PCA Stage from .rtzt file
 Thickness converted to tangential thickness
 10 blades and 1 splitter

Two lines for the number of quasi-orthogonal lines:
 n_qo scale
 23 1.00000

A section that defines the quasi-orthogonal type and end points:
 i    r_hub     r_shr     z_hub       z_shr    n_blade n_curve i_type                         i_row         i_spool
 1   0.00069   0.05594   -0.04959     -0.04959 0        1       1                              0             0
 2   0.00224   0.05215   -0.03682     -0.03757 0        1       1                              0             0
 3   0.00702   0.04941   -0.02481     -0.02527 0        1       1                              0             0
 4   0.01189   0.04776   -0.01284     -0.01277 0        1       1                              0             0
 5   0.01357   0.04720   -0.00004     -0.00018 10       5       3                              0             0

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 6 0.01447    0.04728   0.00570        0.00371        10            5            3             0            0
 7 0.01609    0.04758   0.01128        0.00759        10            5            3             0            0
 8 0.01832    0.04809   0.01664        0.01145        10            5            3             0            0
 9 0.02108    0.04884   0.02175        0.01526        20            5            3             0            0
 10 0.02463   0.04993   0.02700        0.01930        20            5            3             0            0
 11 0.02867   0.05132   0.03188        0.02325        20            5            3             0            0
 12 0.03314   0.05305   0.03637        0.02706        20            5            3             0            0
 13 0.03799   0.05513   0.04045        0.03068        20            5            3             0            0
 14 0.04318   0.05759   0.04408        0.03407        20            5            3             0            0
 15 0.04866   0.06040   0.04726        0.03717        20            5            3             0            0
 16 0.05440   0.06358   0.04995        0.03988        20            5            3             0            0
 17 0.06035   0.06709   0.05214        0.04216        20            5            3             0            0
 18 0.06646   0.07087   0.05379        0.04393        20            5            3             0            0
 19 0.07271   0.07488   0.05485        0.04514        20            5            3             0            0
 20 0.07902   0.07901   0.05538        0.04575        20            5            3             0            0
 21 0.08033   0.08032   0.05544        0.04585         0            1            1             0            0
 22 0.08164   0.08164   0.05548        0.04592         0            1            1             0            0
 23 0.08295   0.08295   0.05550        0.04597         0            1            1             0            0

A section that defines the quasi-orthogonals and the blade geometry:
 i j r_qo     theta_qo  z_qo   thu_qo gamma_r_qo gamma_z_qo
 5 1 0.01357 0.32039 -0.00004 0.00255 -0.18038 -23.15654
 5 2 0.02198 0.26684 -0.00008 0.00244 -0.36249 -32.52025
 5 3 0.03038 0.21411 -0.00015 0.00251 -0.34266 -41.27189
 5 4 0.03879 0.26814 -0.00016 0.00243 -0.00979 -49.73230
 5 5 0.04720 0.29630 -0.00018 0.00234 -0.18913 -57.43224
 6 1 0.01447 -9.69106 0.00570 0.00269 1.88713 -23.08947
 6 2 0.02267 -8.14852 0.00518 0.00256 0.41685 -31.31698
 6 3 0.03087 -7.40827 0.00464 0.00243 -0.99339 -39.39957
 6 4 0.03908 -6.96808 0.00417 0.00230 -2.04619 -47.44992
 6 5 0.04728 -6.75726 0.00371 0.00218 -3.95792 -54.90281
 7 1 0.01609 -18.29413 0.01128 0.00262 3.70754 -22.85821
 7 2 0.02396 -15.68568 0.01033 0.00248 1.15036 -30.47241
 7 3 0.03183 -14.35239 0.00936 0.00234 -1.75718 -37.83696
 7 4 0.03970 -13.58089 0.00846 0.00220 -3.70752 -45.35764
 7 5 0.04758 -13.16589 0.00759 0.00206 -6.69381 -52.39817
 8 1 0.01832 -25.28463 0.01664 0.00254 4.70103 -22.81646
 8 2 0.02576 -22.28703 0.01531 0.00241 1.41759 -29.88146
 8 3 0.03320 -20.61659 0.01398 0.00227 -2.35690 -36.52612
 8 4 0.04065 -19.60303 0.01270 0.00212 -5.03581 -43.43454
 8 5 0.04809 -18.99898 0.01145 0.00196 -8.73336 -50.00039
 9 1 0.02108 -30.92988 0.02175 0.00248 4.74907 -23.14610
 9 2 0.02802 -28.02047 0.02011 0.00234 1.11611 -29.56330
 9 3 0.03496 -26.23881 0.01846 0.00220 -2.97754 -35.52497
 9 4 0.04190 -25.07781 0.01685 0.00204 -6.21556 -41.74088
 9 5 0.04884 -24.32487 0.01526 0.00188 -10.40615 -47.79160
 10 1 0.02463 -36.00322 0.02700 0.00242 3.85677 -23.97254
 10 2 0.03096 -33.42982 0.02507 0.00228 0.15779 -29.56658
 10 3 0.03728 -31.67995 0.02313 0.00213 -3.84908 -34.83600
 10 4 0.04361 -30.43321 0.02121 0.00197 -7.49971 -40.24432
 10 5 0.04993 -29.55790 0.01930 0.00182 -12.07824 -45.67586
 11 1 0.02867 -40.35207 0.03188 0.00236 2.23718 -25.26450
 11 2 0.03435 -38.17139 0.02974 0.00222 -1.42539 -29.89481
 11 3 0.04001 -36.55263 0.02757 0.00207 -5.15749 -34.49204
 11 4 0.04567 -35.29039 0.02542 0.00192 -8.89269 -39.12102
 11 5 0.05132 -34.35094 0.02325 0.00177 -13.85353 -43.85841
 12 1 0.03314 -44.26280 0.03637 0.00232 0.10221 -26.97474
 12 2 0.03816 -42.42247 0.03407 0.00217 -3.48507 -30.56208
 12 3 0.04314 -40.96080 0.03175 0.00203 -6.83731 -34.52932
 12 4 0.04811 -39.72235 0.02942 0.00188 -10.45941 -38.40800
 12 5 0.05305 -38.76700 0.02706 0.00173 -15.90754 -42.28558
 13 1 0.03799 -47.91006 0.04045 0.00228 -2.40966 -29.07832
 13 2 0.04233 -46.32055 0.03805 0.00214 -5.94640 -31.56104
 13 3 0.04663 -45.00031 0.03562 0.00200 -8.93117 -34.88947
 13 4 0.05090 -43.80060 0.03317 0.00185 -12.32638 -38.07380
 13 5 0.05513 -42.85755 0.03068 0.00171 -18.25871 -40.88997
 14 1 0.04318 -51.39712 0.04408 0.00226 -5.26535 -31.52634
 14 2 0.04685 -49.96856 0.04163 0.00212 -8.83099 -32.82496
 14 3 0.05047 -48.75090 0.03914 0.00198 -11.46588 -35.54585
 14 4 0.05405 -47.58476 0.03663 0.00184 -14.51275 -38.15374
 14 5 0.05759 -46.66554 0.03407 0.00170 -20.92644 -39.61549


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 15   1   0.04866   -54.78108   0.04726         0.00224      -8.53323 -34.20149
 15   2   0.05168   -53.43857   0.04478         0.00211      -12.12520 -34.30999
 15   3   0.05464   -52.27642   0.04227         0.00197      -14.44340 -36.45351
 15   4   0.05755   -51.13094   0.03975         0.00184      -17.13253 -38.55727
 15   5   0.06040   -50.22395   0.03717         0.00170      -23.67359 -38.40397
 16   1   0.05440   -58.09399   0.04995         0.00224      -12.36035 -36.91306
 16   2   0.05678   -56.77929   0.04747         0.00211      -15.80725 -36.02020
 16   3   0.05910   -55.62589   0.04497         0.00198      -17.90732 -37.55025
 16   4   0.06137   -54.47843   0.04245         0.00185      -20.39385 -39.11425
 16   5   0.06358   -53.55910   0.03988         0.00172      -26.48486 -37.37148
 17   1   0.06035   -61.35160   0.05214         0.00227      -16.87176 -39.31440
 17   2   0.06211   -60.02598   0.04967         0.00214      -19.92706 -37.88099
 17   3   0.06382   -58.83913   0.04719         0.00201      -21.91242 -38.69098
 17   4   0.06548   -57.66538   0.04469         0.00188      -24.33144 -39.57177
 17   5   0.06709   -56.69062   0.04216         0.00175      -29.09953 -36.76047
 18   1   0.06646   -64.56377   0.05379         0.00231      -22.10267 -40.96566
 18   2   0.06763   -63.20368   0.05134         0.00220      -24.62539 -39.61601
 18   3   0.06875   -61.94636   0.04888         0.00207      -26.48127 -39.65304
 18   4   0.06983   -60.72039   0.04641         0.00195      -28.81198 -39.70950
 18   5   0.07087   -59.63480   0.04393         0.00181      -31.57298 -37.06592
 19   1   0.07271   -67.72621   0.05485         0.00241      -27.77629 -41.34374
 19   2   0.07330   -66.32376   0.05243         0.00231      -29.91973 -40.62141
 19   3   0.07384   -64.96857   0.05000         0.00218      -31.51785 -40.06106
 19   4   0.07437   -63.66663   0.04757         0.00202      -33.54181 -39.54783
 19   5   0.07488   -62.40934   0.04514         0.00194      -34.26011 -38.72800
 20   1   0.07902   -70.87669   0.05538         0.00263      -32.69635 -39.92279
 20   2   0.07904   -69.41995   0.05297         0.00260      -34.43144 -39.83097
 20   3   0.07902   -67.94505   0.05056         0.00239      -36.32393 -39.91470
 20   4   0.07901   -66.52396   0.04815         0.00205      -37.25527 -39.78318
 20   5   0.07901   -65.01019   0.04575         0.00216      -37.35707 -41.84796

A section for additional geometry data:
 j   throat throat_pos clearance max_thick                   te_thick dummy1 dummy2 dummy3
 1   0.00000 0.00000    0.00000 0.00000                      0.00000   0.00   0.00   0.00
 2   0.00000 0.00000    0.00000 0.00000                      0.00000   0.00   0.00   0.00
 3   0.00000 0.00000    0.00000 0.00000                      0.00000   0.00   0.00   0.00
 4   0.00000 0.00000    0.00000 0.00000                      0.00000   0.00   0.00   0.00
 5   0.00000 0.00000    0.00000 0.00000                      0.00000   0.00   0.00   0.00


Appendix D: Example of an Aerodynamic Data File (*.aer)
The following is a described example of an aerodynamic data file:

Three lines to identify the aerodynamic data:
 Radial stage at design flow
 ideal gas
 5 May 2008

Two lines for the reference aerodynamic parameters, which depend on the value of i_flow in the .con
file. Assuming i_flow = 1:
 ref_n        ref_mass     ref_d
 60000.0         1.00     0.15804

Two lines for the Reynolds number:
 Re_ref
 0.0

Two lines for the fluid data, which depends on the value of i_fluid in the .con file. Assuming i_fluid
= 1 (for ideal gas):
 cp_gas     gamma_gas
 1005.2     1.40

Two lines for the number of points on the inlet boundary where flow conditions are specified:

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 n_inbc
 1

Lines for the fraction of the inlet boundary where flow conditions are specified (n_inbc values):
 f_inbc
 0.0

Lines for the pressure on the inlet boundary (n_inbc values, which depend on i_bc in the .con file). As-
suming i_bc = 0:
 pt_inbc
 98000.0

Lines for the temperature on the inlet boundary (n_inbc values, which depend on i_bc in the .con file).
Assuming i_bc = 0:
 tt_inbc
 293.0

Lines for swirl on the inlet boundary (n_inbc values, which depend on i_bc in the .con file). Assuming
i_bc = 0:
 rcu_inbc
 0.00

Two lines for the mixing model and blade transparency model parameters:
 eddy      f_bl_le f_bl_te
 0.0001      0.0     0.0


Appendix E: Examples of Correlations Data Files (*.cor)
EXAMPLE 1

The following example of a correlations data file is for a radial compressor. For most radial compressor or
pump impeller calculations, the only parameter that changes is the small-scale polytropic efficiency. Note
that a single value of the empirical information for flow outlet angle is specified (k_dev = 3 implies the use
of a slip factor, and because k_dev is specified as 0.0 the program calculates the slip factor from the Wiesner
correlation).

Three lines to identify the run (maximum 72 characters per line):
 Typical correlations file for radial compressor
 small-scale efficiency, slip factor of 0.0 (so Wiesner) and no blockage
 5 May 2008

Two lines for integer data:
 i_loss i_dev i_ewb
 1      1     0

Two lines for loss input data:
 n_loss_sl n_loss_qo
 1         1

Two lines for empirical loss data:
 i_qo_loss k_loss f_loss loss
 1    1      0.500 0.86

Two lines for deviation input data:


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 n_dev_sl n_dev_qo
 1        1

Two lines for empirical deviation data:
 i_qo_dev k_dev f_dev dev
 1    3     0.500 0.00

Two lines for blockage input data:
 n_ewb_sl n_ewb_qo
 1        1

Two lines for empirical blockage data:
 i_qo_ewb k_ewb f_ewb ewb
 1    1     0.500 0.00

EXAMPLE 2

The following example of a correlations data file is for a nine-stage radial compressor with a vaneless diffuser
and a return channel downstream of each impeller except the ninth. The losses in this case are specified as
a single polytropic efficiency for everything, and the blockage is zero. But for the deviation of the flow from
the blade angle at the trailing edge it is sensible to use a slip factor of 100 for the impeller and a deviation
angle for the stator vanes. In this case 0.0 is specified as the slip factor so the Wiesner slip factor is used,
and 5.00° is specified for the return channel deviation angle. k_dev controls whether to use the slip factor
or deviation, and i_qo specifies the calculating station at which the slip factor or deviation is applied. A
sensible rule would be to make the value of i_qo equal to the number of the q-o at the trailing edge, but
the program can accept any value between the previous trailing edge and the current one. If there is a
vaned diffuser with a different deviation angle then an additional line with k_dev set to 1 would be needed
between each impeller and return channel line.

Three lines to identify the run (maximum 72 characters per line):
 Typical correlations file for multistage radial compressor
 Efficiency, slip factor in impeller, deviation in stators, no blockage
 18 September 2008

Two lines for integer data:
 i_loss i_dev i_ewb
 1      1     0

Two lines for loss input data:
 n_loss_sl n_loss_qo
 1         1

Two lines for empirical loss data:
 i_qo_loss k_loss f_loss loss
 1    1      0.500 0.80

Two lines for deviation input data:
 n_dev_sl n_dev_qo
 1        17

Lines for empirical deviation data:
 i_qo_dev   k_dev f_dev dev
 1    3     0.500   0.00
 45   1     0.500   5.00
 65   3     0.500   0.0


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                                                                                                                                     Appendices

 95    1   0.500     5.00
 115   3   0.500     0.0
 145   1   0.500     5.00
 165   3   0.500     0.0
 195   1   0.500     5.00
 215   3   0.500     0.0
 245   1   0.500     5.00
 265   3   0.500     0.0
 295   1   0.500     5.00
 315   3   0.500     0.0
 345   1   0.500     5.00
 365   3   0.500     0.0
 395   1   0.500     5.00
 415   3   0.500     0.0

Two lines for blockage input data:
 n_ewb_sl n_ewb_qo
 1        1

Two lines for empirical blockage data:
 i_qo_ewb k_ewb f_ewb ewb
 1    1     0.500 0.00

EXAMPLE 3

The following example of a correlations data file is for a radial turbine stage with an inlet nozzle and an
impeller. In the example shown, the losses are different for the two components. The deviation angle is
specified by use of the cosine rule for both components (k_dev = 5) but a correction to this (2.00°) is applied
in the rotor.

Three lines to identify the run (maximum 72 characters per line):
 Typical correlations file for radial turbine stage
 Efficiency, deviation as mod to cosine rule and no blockage
 18 September 2008

Two lines for integer data:
 i_loss i_dev i_ewb
 1      1     0

Two lines for loss input data:
 n_loss_sl n_loss_qo
 1         2

Three lines for empirical loss data:
 i_qo_loss k_loss f_loss loss
 1    1      0.500 0.88
 35   1      0.500 0.75

Two lines for deviation input data:
 n_dev_sl n_dev_qo
 1        2

Lines for empirical deviation data:
 i_qo_dev k_dev f_dev dev
 1    5   0.500   0.00
 35   5   0.500   2.00

Two lines for blockage input data:


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 n_ewb_sl n_ewb_qo
 1        1

Two lines for empirical blockage data:
 i_qo_ewb k_ewb f_ewb ewb
 1    1     0.500 0.00

EXAMPLE 4

In all of the above examples, a constant value of the empirical information is applied on all streamlines, so
only a single value is specified. An additional feature is that the program also allows this data to vary across
the span for each blade row. Then there would be an additional line for each fraction of the span. This is
shown with regard to the losses, which specifies the efficiency at 0%, 25%, 50%, 75% and 100% of the span.

Three lines to identify the run (maximum 72 characters per line):
 Radial compressor impeller with spanwise variation of eta
 Efficiency, slip factor for impeller with no blockage
 18 September 2008

Two lines for integer data:
 i_loss i_dev i_ewb
 1      1     0

Two lines for loss input data:
 n_loss_sl n_loss_qo
 5         1

Lines for empirical loss data:
 i_qo_loss k_loss f_loss loss
 1    1      0.000 0.77
 1    1      0.250 0.79
 1    1      0.500 0.80
 1    1      0.750 0.79
 1    1      1.000 0.77

Two lines for deviation input data:
 n_dev_sl n_dev_qo
 1        1

Lines for empirical deviation data:
 i_qo_dev k_dev f_dev dev
 1    3   0.500   0.00

Two lines for blockage input data:
 n_ewb_sl n_ewb_qo
 1        1

Two lines for empirical blockage data:
 i_qo_ewb k_ewb f_ewb ewb
 1    1     0.500 0.00

EXAMPLE 5

The following example of a correlations data file shows the use of a blade oriented specification for the
Kacker Okapuu correlations for an axial turbine calculation. No blockage is specified.


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Three lines to identify the run (maximum 72 characters per line):
 Typical correlations file for axial turbine - no blockage
 Kacker-Okapuu
 10 September 2008

Two lines for integer data:
 i_loss i_dev i_ewb
 2      2     0

Two lines for loss input data:
 n_loss_bladerow dummy
 1         1

Two lines for empirical deviation data (i_loss = 2):
 i_blrow i_loss_type f_loss(1) f_loss(2) f_loss(3) f_loss(4) f_loss(5) f_loss(6)
 1       1           1.0       1.0       1.0       1.0       1.0       1.0

Two lines for deviation input data:
 n_dev_bladerow dummy
 1              1

Lines for empirical deviation data:
 i_blrow i_dev_type f_dev(1) f_dev(2) f_dev(3) f_dev(4) f_dev(5) f_dev(6)
 1       1          0.0      0.0      0.0      0.0      0.0      0.0

Two lines for blockage input data:
 n_ewb_sl n_ewb_qo
 1        1

Two lines for empirical blockage data:
 i_qo k_ewb f_ewb ewb
 1    1     0.500 0.00

EXAMPLE 6

The following example of a correlations data file shows the use of a blade oriented specification for the
Miller-Wright correlations for an axial compressor calculation.

Three lines to identify the run (maximum 72 characters per line):
 Typical correlations file for multistage axial compressor
 Miller Wright Correlations
 10 September 2008

Two lines for integer data:
 i_loss i_dev i_ewb
 2      2     2

Two lines for loss input data:
 n_loss_bladerow dummy
 1         1

Two lines for empirical loss data (i_loss = 2):
 i_blrow i_loss_type f_loss(1) f_loss(2) f_loss(3) f_loss(4) f_loss(5) f_loss(6)
 1       11          1.0       1.0       1.0       1.0       1.0       1.0



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Two lines for deviation input data (i_dev = 2):
 n_dev_bladerow dummy
 1              1

Lines for empirical deviation data (i_dev = 2):
 i_blrow i_dev_type f_dev(1) f_dev(2) f_dev(3) f_dev(4) f_dev(5) f_dev(6)
 1       11          0.0      0.0      0.0      0.0      0.0      0.0

Two lines for blockage input data:
 n_ewb_bladerow dummy
 1        1

Two lines for empirical blockage data:
 i_blrow i_ewb_type f_ewb(1) ... ... .... ... f_ewb(6)
 1       11         1.0      1.0 1.0 1.0 1.0 1.0


Appendix F: Troubleshooting
The Vista TF program and numerical method is extremely robust, especially in unchoked flows and when
running from an existing restart file. There should generally be no numerical problems with radial compressor,
radial turbine, and radial pump calculations, which are the first applications for which the program has been
released. Nevertheless convergence problems and unexpected program errors can still occur. The most
common problems are format errors in the input data or numerical problems inherent to the streamline
curvature method or associated with choking. The numerical errors can sometimes result in a failure of the
solution to converge or even a complete breakdown as the compiled program encounters a FORTRAN error,
such as the square root of a negative number, or a floating point overflow. The most common of these are
trapped and reported by the program. It is hoped that all such errors can be removed in a later version. The
compiler of course will report these errors, but this is not of much use to the user. The most likely cause of
such errors is a data error. The sections below outline typical problems and suggest solutions for these with
some advice on how to deal with input format and data errors.

If the solution converges to the user-specified level of convergence then the program exits normally with
a value of 0 in the command line (CALL EXIT(0)). If the solution has not converged but the maximum number
of iterations has been reached, then a value of 1 is returned. If the program has identified some serious
difficulty which has an appropriate trap, then the program exits with a negative return value and prints an
appropriate error message. Only the most common errors have been supplied with a trap against such errors.
If the program identifies a feature of the input data which it determines may lead to some difficulties (rota-
tional direction, grid aspect ratio, inconsistent flow and speed data) it prints a warning to the screen and
the output file. This information may help to correct the data errors.

Some examples of warnings and error messages are as follows:
 WARNING: Anti-clockwise rotation

 Vista TF suspects that the first rotor blade is counter-rotating

 Possible cures:

 (a)
 Change value of i_flow to be negative
 (b)
 Change geometry from left-handed to right-handed or vice versa


 WARNING: Wilkinson damping factor used
 Damping factor damp_sc reduced by Vista TF to value suggested by Wilkinson

 WARNING: error increasing -relaxation factors reduced 5%


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 ERROR: Error noted in subroutine throughflow_manager

 ERROR TYPE: error_max > 400%

 ERROR PARAMETERS: -10 10 17 139 0 0

 0.2100E+16 0.5600E+00 0.7250E+00 0.2905E+01 0.0000E+00

 Problem: Near to choke on quasi-orthogonal: 17 on iteration: 139
 Inlet mass flow: 0.56000
 Local estimated choke mass flow: 0.72497
 Local effective relative Mach number: 2.90494
 Possible cures:


 (a)
 Remove this q-o from domain
 (b)
 Check consistency of flow and speed


Input-output Errors
If the program fails to run at all, then this is usually a sign that some of the formatted input data is not
correct (no empty lines where these were expected, or an empty line where data was expected, or similar
formatting problems). The screen monitor information then says that the file has broken down in a particular
input subroutine; this provides a clue for identifying which file has an incorrect format. Most straightforward
errors caused by new users or new cases are related to the data input files, which are fairly rigid with regards
to the lines of data and which do not accept an empty line where a line of data should be. No built-in con-
sistency checks of the input data are made, so errors of this nature can easily occur, especially at the beginning
of a completely new calculation. To help avoid this type of error, you can copy lines from similar existing
input files.

The program might report the name of the input file that contains an error. Should such errors happen, you
should examine the .hst file where the input data is recorded. From this, you can determine which file has
not been correctly read or might have errors, and also which part of that file has been successfully read.

If the program reads all the input files, starts successfully but then fails before the iterations begin, then this
is often a problem related to the specified flow and speed conditions in the input data or the geometry
specification, and these should be checked. These errors are usually related to errors in the units of the
specified data (flow conditions, boundary conditions, geometry, empirical data, and so on). A typical user
error of this type is that the diameter is needed as a reference value for the size in the flow information
(.aer), but the user specifies a radius because the coordinates in the geometry file (.geo) are radius values.
Another common error with users is to specify the geometry in inches rather than meters. Another typical
user error of this type is that the pressure is specified in bars whereas it is expected to be in N/m2. Other
errors may be related to the fact that the specified flow conditions imply choked flow or reverse flow. A
useful consistency check of the flow data is made where the following information is printed:
 Vista TF: Axial compressor calculation
 --------------------------------------
 Estimated mean flow coefficient cm/u at first rotor inlet = 0.4567
 Estimated mean Mach number cm/a at first rotor inlet      = 0.4426

These values may be used to identify if the mass flow, speed and other data have been specified sensibly,
as typical values of these parameters for each type of machine will be known.

If the program runs, but breaks down after only a few iterations, then this can often be a sign that some of
the input data is still not correct because the program is generally very reliable. Here the strategy is to reduce
the value of the maximum number of iterations to a lower value than that at which the flow breaks down
(reduce the value of the parameter max_it_main in file .con), to rerun the case, and then to examine

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the results in the .hst and .out files. The errors are usually related to mistakes in the specified data (such
as flow conditions, boundary conditions, geometry, and empirical data) rather than mistakes in the numer-
ical method, and these data problems can then often be identified from un-converged results or values
provided in the .hst, .txt and .out files. It can also be useful at this stage to examine the plot files of
the initial geometry set up by the program, which is named test_prefix.txt or test_prefix.csv.
This can often identify aspects of the geometry or flow data that are inconsistent.

If the program runs, but the results are extremely unexpected, such that a pump impeller or a compressor
stator blade row has been interpreted by the program as a turbine row, then the blade angle definition
should be checked. The program attempts to identify the type of blade row from the geometry specified,
but in some cases the rules that have been programmed may fail. For example, a compressor stator is
identified as a stator blade row which turns the absolute flow towards the meridional direction, that is the
blade angle decreases from the leading edge to the trailing edge through the blade row. In some special
cases, such as an axial compressor stator with a degree of reaction above 100% or rotor blades with extensive
local leading edge recamber, the blade may have other blade forms. In these cases it is possible to specify
additional data in the geometry file (see parameter i_row below) to overwrite the program’s own attempts
at blade type identification. Geometry produced by BladeEditor contains blade type information provided
that, in the blade feature within BladeEditor, a blade type (rotor or stator) is specified.

Convergence
The program has several different internal convergence checks, but a converged solution can be achieved
only if all of the internal loops also converge, so only one convergence criterion really needs to be checked,
which is the convergence of the meridional velocity.

The most important convergence check is the maximum error of the local meridional velocity anywhere in
the flow field, expressed as a percentage of the local meridional velocity and denoted as error_cm (%)
on the screen and in the output files. During the iteration process, the maximum value of the change in the
meridional velocity in the whole flowfield between one iteration and the next (delta_cm %) and the loc-
ation of the maximum error is printed onto the screen every 10 iterations and into the history file for each
iteration. The local value of this error is also printed in the output file and into the .csv and .txt plot
files. To achieve convergence near machine accuracy, use a maximum value of 0.01% as a convergence cri-
terion. Note that this corresponds to a maximum residual error in CFD terminology of 0.0001, that is 1E-04,
which is a much more stringent criterion than the RMS residual error often used in CFD programs of 1E-04.
The value of the local error is output for examination with plot software and, for cases that have not con-
verged, it is worthwhile to examine the location of the maximum as this may identify the location of the
problem.

It is important to remember, however, that numerical methods have many sources of error. In a throughflow
calculation, the so-called model errors, related to the fact that the equations we are solving do not really
describe the real flow particularly adequately (in this case we solve for inviscid, circumferentially-averaged
mean values on widely spaced grid lines) probably outweigh all other sources of error. A solution that is
converged to a maximum error in meridional velocity of 0.5% is likely no worse in terms of its agreement
with reality than a solution that converges to 0.01% or lower. So calculations that converge to 0.5% can also
be considered to be converged for practical engineering purposes.

The second convergence check occurs in the innermost mass-flow iteration loop where the program monitors
the number of loops required to solve the continuity and radial equilibrium equations on each calculating
station. The maximum value of the number of mass flow iterations and the location of the quasi-orthogonal
where this occurred is also printed onto the screen and into the .hst file. You can specify the maximum
number of loops for the internal mass-flow iteration loop with the max_it_mass parameter in the control
file. The recommended value for this parameter is 10. Early in the run, the program usually stops the internal
loops when the value of max_it_mass is reached. Later, as convergence is approached, less then 10 internal

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loops are generally required. A typical converged solution may require only 1 or 2 internal loops. The error
in the mass flow should be tighter than that for the meridional velocity; a value of 0.001% is currently re-
commended.

The third convergence check occurs in an iteration to a specified pressure ratio and is related to the conver-
gence of the inlet mass flow to a final value and the convergence of the specified target pressures at the
trailing edges to a fixed value. These are written onto the output file as error_p and error_mass respect-
ively. The same limit for the mass flow convergence is used as given above and the target pressure conver-
gence is set internally within the program to be tighter than this. Experience shows that it is important in
simulations to a specified pressure ratio to ensure that tight tolerances on these parameters are given, oth-
erwise the program modifies the target pressures on the basis of inadequately converged data and divergence
may result.

In some cases with closely spaced calculating stations (high aspect ratio grid) it has been identified that,
although the simulation converges to a relatively low level of the maximum error in the meridional velocity
of 0.1% relatively quickly, it does not always continue to converge below this level of error. In these cases
you have several options. Firstly, it might be sensible to accept this level of convergence and continue to
optimize the geometry of the machine. In some cases, the simulation that is not perfectly converged may
indicate the existence of an unwanted flow feature as a cause of the poor convergence. Such features include:
anything that creates a tendency for the flow to reverse direction; an extremely high curvature in the meri-
dional channel; a poor grid. A second approach is to make use of other models that are built-in for the
damping factors within the program, by reducing the value of the streamline curvature damping factor
damp_sc and the velocity level damping factor damp_vl. In some cases it may be helpful to reduce both
the value of damp_sc and damp_vl to smaller values than the standard values of 0.25 and 0.40.

The most common failure for the program to converge is related to difficulties in the streamline curvature
calculation causing divergence of the maximum error in the meridional velocity distribution. If the program
identifies a trend for the results to start to diverge then it automatically decreases the damping factors to
avoid divergence by causing more damping of the solution. If the errors continue to increase, then further
reduction of the relaxation factors tends to freeze the unconverged iteration at the state where the problem
was identified so that there is at least no unexpected exit from the program even if the simulation does not
converge. Because of this feature it is not advisable simply to increase the number of iterations in the hope
that the simulation will converge. A better strategy is to calculate with a large number, say 2000 iterations,
and if the simulation does not converge, restart the calculation from the restart file to reset the damping
factors to sensible values. This strategy often works in difficult cases.

The numerical fix of reducing the damping factors when the error diverges is reported on the screen and
in the history file. If this fix does not work, then the calculation of the streamline curvatures may ultimately
fail, although this only occurs in simulations that have otherwise started to have serious numerical problems.
The ultimate failure here tends to be an error in the subroutine pero, called from subroutine curvature,
or in subroutine parabola, called from subroutine streamlines. Both are, in themselves, generally robust.
Subroutine pero is a modified interpolation routine along the lines of the so-called AKIMA splines. The
breakdown is related to the numerical difficulty of calculating curvatures in a flow when the streamlines are
no longer smooth and the spacing of the calculating planes is small. Subroutine "parabola" attempts to fit
a parabola through internal data in the program and is also robust until serious problems occur. These errors
have mostly been trapped such that an error message is printed and the program exits the calculation
without breaking down.

In cases where such problems occur, it is often worthwhile simply to run the simulation again from the restart
file generated from an earlier unconverged simulation or with a different initial estimate of the flowfield
(which is controlled through the initial value of cm_start in the control file), because starting from better
initial conditions may clear the problem found in the initial calculation. In choked flows it is generally better
to start with a lower value of cm_start, as this will not be choked. If this does not work then again a

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useful strategy is to reduce the value of the maximum number of iterations to a lower value, say 200 (para-
meter max_it_main in file .con), and recalculate and examine the unconverged results. It may also help
to run the simulation repeatedly with a low limit on the maximum number of iterations because each suc-
cessive run tends to get to a lower value of the maximum error. If this fails, it is useful to examine the .hst
and .out files and plots of the unconverged results. These files and plots can be used to identify aspects
of the design that, when improved, allow convergence to be achieved.

The program also writes the values of the local error and the local choke ratio into the .txt file so it is
possible to examine this and quickly locate the location where the problems are occurring. A value of unity
for the choke ratio implies that the flow is choked and a value above unity indicates that the local mass
flow is above the choking mass flow of the streamtube. It may be necessary to have some fundamental
understanding of how the turbomachine operates in order to identify how to remove these problems. Further
comments on choking are given in Choking (p. 142).

The program prints an error message if it reaches a state where the maximum change in meridional velocity
from one iteration to the next is more than 400% and then it closes down the calculation. Should this occur
it is then recommended that you repeat the calculation with the maximum number of iterations set at a
value lower than that where the program stopped (see the history of iterations in the output file) and then
examine the results for this unconverged point. This can help you to identify the problem.

Reverse Flow
Another common failure mode for the program where it has difficulties converging is related to difficulties
in calculating reverse flow in the meridional plane; such flow is not possible with the streamline curvature
method. If the program observes that reverse flow occurs in the meridional plane, then it attempts temporary
fixes to enable the iterations to proceed in the hope that the problem will be cleared. One particularly im-
portant fix (that is not reported) is to avoid negative values of the meridional velocity by setting any negative
values to 5% of the mid-span value. This may be used in early iterations and later no longer be needed, but
if the final “converged” result contains such values, it is not really a valid solution. This can often be identified
by a difficulty in convergence at a particular location in the grid. The background to this problem is a fun-
damental difficulty related to the physics, whereby a strongly swirling flow in an annular duct may separate
at the hub or shroud, and the streamline curvature method is inherently unable to calculate such a reverse
flow. This problem becomes more serious with calculations of low hub-to-tip ratio. The use of a limit on the
meridional velocity on any streamline is reported in the output.

Choking
It should be mentioned that the throughflow method is not particularly suitable for choked blade rows because
the mean stream surface equations average out the flow in the circumferential direction and are therefore
not aware of high Mach numbers on the suction surface of blades. In addition, any shocks that may be
present in turbomachinery flows are generally not oriented in the circumferential direction so are smeared
out in the circumferential averaging of the flow to determine the mean stream surface. Furthermore, the
basic method is inviscid and this precludes the existence of strong shocks.

Nevertheless, despite these serious limitations, an attempt has been made to model choking in the blade
rows so that, in combination with correlations, the maximum flow and the additional losses related to shocks
are taken into account in the overall predicted performance. In this way, the program includes aspects of
choking that are compatible with the level of empiricism of typical 1D calculation methods, and may even
be more successful than these because the variation of Mach number over the span is taken into account.
This is useful in a program intended for design purposes because it helps choking problems to be identified
at a relatively early stage in the design process, and aids the understanding of the axial and radial matching
of the blade rows as the rotational speed varies.



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All aspects of special calculations for choking flows are hidden. Setting the parameter i_expert = 0
causes the program to examine choking but not limit the mass flow if choking is found to occur. This is the
most robust way to run the program and is recommended for beginners. Expert users can use i_expert
= 1, which limits the mass flow according to various choke models.

Choking is strongly related to the throat areas between two blade rows, so any real estimate of the choking
flow should make use of accurate estimates of the throat areas. In Vista TF the shortest straight-line distance
between two blade rows can be specified in the geometry file for each of the input sections, and if the values
are not specified (that is, a value of zero is given) then Vista TF makes its own crude estimate of the throat
areas based on its limited knowledge of the blade geometry. This estimate is, at the moment, too crude to
be used accurately in the calculation of choked blade rows, and may lead to a value for the choked mass
flow that is incorrect. It may be worthwhile, in some situations, to run Vista TF with no values specified for
the throat and then examine the program´s own estimate of the throat areas, which are in the output file,
and then run with slightly larger or smaller values specified in the geometry file, depending on the real
throat areas or the choking mass flow if the latter is known.

One method that tends to work in the most difficult cases is to remove any calculating planes in the
neighbourhood of the throat, as suggested by Denton (1978). Local details of the flow calculation are lost,
but the calculation can then be made to converge up to the limiting mass flow.

When you specify a mass flow rate, you must ensure that it is not greater than the choking value. The program
may generate warning messages if the specified mass flow exceeds the choking value.

The output parameter choke_ratio is the ratio of the local mass flux to the maximum possible at that
location. A value above unity is not a realistic solution but if the choke parameter i_expert is set to zero
then such solutions can be generated. This option is available because the program is sometimes more robust
under this operating mode than when i_choke is set to 1 and the full choking models are used. Note that
in some multistage computations the actual specified mass flow may be below that required to actually
choke the machine, but during the iterations, individual blade rows may still become choked. The program
becomes less robust as choking is approached.

In some high-speed situations where it is difficult to obtain convergence with a specified mass flow, the restart
file can be used to store results for a converged operating point at a lower speed and lower flow, and then
the required operating condition can be obtained by starting from the restart file with new flow conditions
slowly stepping to the required operating point. In a similar way, it is advisable to first set up a simulation
close to the design flow, before attempting to move towards a higher flow with a higher risk of choking.

You can run a simulation with a specified pressure ratio. For a choked blade row, the shift to a specified
pressure ratio is a more physical approach than specifying the mass flow because, in this case, the solution
is indeterminate. In turbines with steep characteristics (little variation in mass flow with pressure ratio) this
is reliable. In compressors with flat operating characteristics (large variation in mass flow with pressure ratio)
this approach may be more unstable so it is not recommended for calculations close to the expected surge
line.

Iteration to a defined pressure ratio makes use of the so-called “target pressure” ratio method of Denton
(1978). This requires the program to make a first guess of the pressure at each trailing edge of the machine.
The algorithm currently incorporated makes a crude estimate of this but it has been found that this may
not be sufficient to secure convergence, especially for compressors. For this reason, you have the option to
define the first guess of the pressure at each trailing edge (set i_flow = 6 instead of i_flow = 5).
Even when using this option, the iteration to pressure ratio for multistage compressors is still very sensitive,
and convergence is not guaranteed. If iteration to pressure ratio is used for choked blade rows, then an ac-
curate estimate of the throat widths needs to be provided in the geometry file and the value of i_expert



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should be set to 1 so that the limits to the mass flow at choke are imposed. If the throat area feature is
calculated by BladeEditor then the throat widths will be calculated and added to the geometry file.

Computational Grid
As in most numerical methods, a finer grid leading to a closer spacing of the quasi-orthogonal lines and
streamlines will lead to a higher numerical accuracy of the simulation. Closer spacing of the quasi-orthogonal
lines for streamline curvature calculations can, however, cause instabilities in the convergence process. This
can be overcome by increasing the numerical damping (lowering the relaxation factors) but this causes an
increase in computational time, so a compromise is generally needed.

The relationship between the needed relaxation factors and the aspect ratio of the computational grid in a
throughflow calculation was theoretically derived in a classical paper by Wilkinson in 1970 (see Streamline
Curvature Throughflow Theory (p. 118)). His studies showed that close spacing of the quasi-orthogonal lines
required more damping. The problem is related to the fact that if the calculating stations are closer together
then a small displacement of a streamline can lead to a large curvature. In this case it is only possible to
take a small part of the new solution forward each iteration and so the number of iterations increases.
Wilkinson derived an equation of the following form to calculate the optimum relaxation factor for a certain
grid aspect ratio:




He also showed that the value given here as k2 is actually a function of the Mach number, the flow angle,
and of the method used to calculate the curvature of the streamlines. The aspect ratio of the grid (h/∆m)
in this equation is the ratio of the calculating station length to the meridional spacing of the grid lines. The
equation above was used in older versions of Vista TF to determine the streamline curvature relaxation factor
with the numerical values of k1 = 0.5 and k2 = 20/96. The value was based on the largest aspect ratio that
can be found in the domain. This is then further reduced if the calculations show any tendency to diverge
during the iterations. The largest aspect ratio in the whole grid was used, whereby the meridional spacing
is the shortest meridional distance between the two adjacent grid lines.

A value of 0.01 for this relaxation factor corresponds to an aspect ratio of around 15 and will lead to long
calculation times because only 1% of the new solution can be taken into account and 99% is carried forward
from the earlier solution. In order to reduce an error in the initial solution to 0.01% of its initial value then
the number of iterations required would be




A value of 0.001 for this relaxation factor (aspect ratio near to 50) would lead to ten times as many iterations.
Values of the aspect ratio larger than 15 are therefore not recommended but in cases where this is unavoidable
(such as low aspect ratio blades with high span and small chord with internal calculating stations) then the
program still converges but at a slower rate.

A different stability scheme has been incorporated in Vista TF. In this, the relaxation factor ratio is calculated
as:




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                                                                                                                                    Appendices




Where alpha is the absolute flow angle in ducts and stator rows and the relative flow angle in rotor rows.
In the new scheme, the relaxation factor can vary from quasi-orthogonal to quasi-orthogonal so that regions
of the grid with small aspect ratios are not penalized by a locally poor grid spacing elsewhere. In addition
to this improvement, experience with many difficult cases has been incorporated in the selection of the
maximum relaxation factor. With this new model, you should not need to adjust the damping factors because
the program does this automatically.

All flow gradients in the radial equilibrium equation and the curvature of the streamlines in the solution are
determined by a piecewise parabolic interpolation through three points. This is a very rapid numerical pro-
cedure but experience shows that this can cause errors in the estimation of the curvature of the hub and
casing if the quasi-orthogonal spacing is too wide. For the case of an axial to radial bend with circular arc
meridional wall contours the error in curvature is of the order 2.5% on a grid with 7 quasi-orthogonal lines
(a quasi-orthogonal placed every 15° around the bend). This decreases to 0.2% for 19 quasi-orthogonals (a
quasi-orthogonal every 5°). This suggests that typical radial impellers with an axial inducer should be calculated
with around 15 quasi-orthogonals in the bladed region. Moreover, the basic assumptions of the meridional
throughflow method (for example: no frictional forces, axisymmetric flow, no spanwise mixing) certainly
cause larger errors than this error in the curvature estimate.

It should be noted that decreasing the convergence tolerance to low values does not eradicate this error,
so that for typical engineering applications a tolerance of 0.1% on cm is generally adequate because the
curvature calculation is not more accurate than this. A lower value is however generally used because this
confirms that numerical convergence has really happened.

Using 17 streamlines across the span is recommended. The use of such a large number of streamlines across
the span brings little improvement in the accuracy when compared with experimental data compared to
using only 9, but nevertheless clearly leads to fewer numerical errors in the integration of the radial equilib-
rium equation. 17 and 9 streamlines have the advantage that the streamlines split the flow uniformly into
16 or 8 streamtubes.

The limitations mentioned above on the calculation of flow gradients and curvature also determine to what
extent details of steps in the wall geometry can be taken into account. Steps, kinks and wells in the meridi-
onal contour need to be omitted as these features are typically of a sub-grid size. Generally attempts to
improve the accuracy by using finer grids with more details are not made in streamline curvature calculations
because this is counterproductive.

In axial turbomachinery calculations with quasi-orthogonals at the leading edge and trailing edge planes
and with flare on the hub and casing walls, inaccuracies will arise because the kinks in the contours cannot
be accurately modeled.

Other Numerical Issues
Computing a new solution from the restart file of an existing solution, even when no changes have been
made in the input data, generally requires 50 or more iterations to re-converge to the solution on the restart
file. This effect is due to the fact that the restart file stores only a small part of the information related to
the original solution, and many fine details of the solution have to be recalculated.

In running the program from a cold start (without a restart file) it is useful to think carefully about the initial
value of cm_start that is specified for the control file. This determines the meridional velocity level of the
initial solution and it has been experienced that an initial value too far from reality may cause the solution

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Vista TF

to breakdown. The value that should be specified for cm_start is the flow coefficient (cm/u) of the machine
concerned, whereby the reference velocity used is the velocity determined by the reference diameter and
reference speed (ref_d and ref_n). In flows with a risk of choking, it is better to use a low value of
cm_start to ensure that the initial conditions are not close to choke. When a converged solution is available
as a restart file, it should be used because, although it does not necessarily reduce the number of iterations
needed, it does make the solution process more robust.

The restart file is continually updated by each converged computation, but also if the solution reaches the
limit of the maximum number of iterations without converging. In a case where the solution is actually di-
verging, the non-converged restart file might be a worse starting condition than the program´s own initial
guess, so it can be useful to discard this and start again. If a converged solution has been reached then it
is sometimes useful to store the converged restart file for a better starting solution if something later goes
wrong during calculations at other operating points.

As with all numerical methods, the use of unconverged results for design decisions is extremely dangerous
and is not recommended. Nevertheless, examination of unconverged results can often be extremely useful
for identifying numerical issues. In some cases examination of unconverged results may indicate features of
the design that can be changed to avoid such problems by modification of the geometry.

One measure that has been incorporated and which may be useful during debugging of a poor calculation
is to set the parameter grad_ree equal to zero. This overrides the radial equilibrium equation and leads
to a spanwise constant meridional velocity (see below). This can be useful in identifying errors where flow
data is inconsistent with the geometry being calculated. Another alternative that can be used with turbines
is to specify a near-zero swirl velocity on the mid-streamline at the outlet of the last rotor and let the program
determine the mass flow and pressure ratio consistent with this (“iteration to outlet swirl”). This has unfortu-
nately not been thoroughly tested on enough cases to guarantee that it will always work.

If all else fails then set i_ree = 3 in the control file. Under these circumstances the value specified as
grad_ree in the control file is then used to reduce the meridional velocity gradient as follows:




This can be extremely useful for debugging, because it can allow the program to avoid failing due to high
spanwise velocity gradients. In this way, it effectively becomes a mean-line program with no spanwise variation
in meridional velocity (if grad_ree = 0.0). Other parameters such as the blade speed still vary across
the span, so it is not exactly a mean-line program. Most cases converge under these conditions and this
ensures that the axial matching along the mean streamline of the blade rows is approximately correct. When
converged it may be possible to approach a solution with the correct radial distributions by slowly relaxing
the value of grad_ree towards unity. During this process, the features of the velocity gradients that cause
trouble slowly become part of the calculation and this can then help to identify the problem.

Cases that do not converge well are usually either poor designs, or are good designs operating a long way
from their design point. Non-convergence generally means that the design is a long way from satisfying the
condition of radial equilibrium. If the flow solution converges well then this usually means that the flow is
automatically close to radial equilibrium and this will generally indicate a higher-quality machine.




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                                                                                                     Conversion of a .rtzt File into a .geo File

Appendix G: The RTZTtoGEO Program
The ANSYS .rtzt and the Vista TF .geo Geometry Definition File
The data in the .rtzt file is the meanline coordinate data as produced by the program BladeGen on a
number of layers from hub to shroud, with a format as described in Description of the RTZT File (p. 150). There
are several differences to the .rtzt option in BladeGen and the geometry actually needed by a throughflow
program, and for this reason the RTZTtoGEO program has been written to convert this data into a more
suitable format, rather than working directly with the .rtzt file.

The first difference is related to the need for a throughflow program to work with blade angles, in the case
of Vista TF with the blade lean angles gamma_r and gamma_z (see Definition of Blade Lean Angles (p. 128)).
Throughflow programs work on relatively coarse grids and so it is sensible to provide the programs with
the blade angles rather than just the blade coordinates. Otherwise the blade angles would have to be calcu-
lated by interpolation and differentiation on a coarse grid which will lead to errors. In axial duct flow programs
with planes just at the leading and trailing edges, this is done by specifying the axial blade angles or flow
angles at the inlet and the outlet. In Vista TF, which includes the blade force in the solution and is designed
for radial machines, both the axial and the radial lean angles (gamma_r and gamma_z) have to be defined
and, because the program includes internal planes, these are defined throughout the blade, not just at the
edges.

The second key difference is that RTZT concentrates on the information required on each stream-surface (or
layer) at a certain percentage of the span of the blade, or on blade sections or layers. Throughflow programs
concentrate on the information in a plane at right angles to this and require information along equally
spaced quasi-orthogonal lines at fixed meridional positions through the blade rows, and upstream and
downstream. In .rtzt files, the number of points and spacing in the meridional direction is not the same
on each layer. In a throughflow program, it is the location of the layers on each quasi-orthogonal line that
may be different, but the points along the streamline must be evenly spaced for all layers.

The throughflow program also needs additional data upstream and downstream of a blade row to define
the position of the quasi-orthogonal in a region of duct. This is not the case in the current .rtzt file, because
different levels of information are available on each layer in this region, and curved quasi-orthogonals outside
of the bladed regions are difficult to define. In some of the cases tested with highly curved leading edges,
it was necessary to modify the .geo file by hand to avoid problems with the quasi-orthogonals upstream
or downstream of the leading edge crossing the leading or trailing edge.

Conversion of a .rtzt File into a .geo File
A program, RTZTtoGEO, can be used to generate the geometrical input data file (file extension .geo) for
the Vista TF streamline curvature program from the BladeGen RTZT output format (file extension .rtzt).
The RTZTtoGEO program can be obtained from PCA, although the preferred method to generate the .geo
file is to use the BladeEditor VistaTFExport feature (see Export to Vista TF (.geo) (p. 46)). No guarantee can
be given that the RTZTtoGEO program will work on all cases. This program can be used to merge several
separate .rtzt files from BladeGen into a single .geo file for multiple-blade-row simulations with Vista
TF.

For a single blade row, the program makes use of three files:

 •   One input data file is needed: RTZT geometrical data file (.rtzt).
 •   The program creates one output file: Vista TF geometrical data file (.geo).
 •   The input and output file names are specified by you in an auxiliary data file that must be called
     rtzt.fil. It must contain the necessary file names in the following order and form:


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Vista TF

 Number of blade rows                              1
 RTZT datafile name                                impeller.rtzt
 Vista TF geometry datafile name                   impeller.geo

For multiple blade rows, additional .rtzt files are needed for each blade row and the associated .geo
files are merged into a single .geo file for the whole domain. The number of individual blade rows is given
in the first line and the names of the individual .rtzt files follow this.

For n blade rows the program makes use of n+2 files:

 •    n input data files are needed: n RTZT geometrical data files (.rtzt).
 •    The program creates one output file: Vista TF geometrical data file (.geo).
 •    The input and output file names are specified by you in an auxiliary data file that must be called
      rtzt.fil. It must contain the necessary filenames in the following order and form:
 Number of blade rows                              n
 RTZT datafile name                                Prefix1.rtzt
 RTZT datafile name                                Prefix2.rtzt
 : :
 RTZT datafile name                                Prefixn.rtzt
 Vista TF geometry datafile name                   impeller.geo

Note that the different .rtzt files must be generated from BladeGen files that join up to each other con-
sistently with no gaps. If the domains between adjacent blade rows as defined by the .rtzt files meet
exactly at the boundary of the domains then the program includes a single quasi-orthogonal at this
boundary.

Running the RTZTtoGEO Program
The file impeller.rtzt and the file rtztgeo.fil should be in the same directory as the executable
of the compiled program files. Starting the program produces the .geo file from the .rtzt file. If the .geo
file already exists, there is a prompt as to whether this should be overwritten.

The program prompts you to identify whether the blade row is a compressor (pump) or turbine, and
whether it is a rotor or stator. In addition the program suggests the number of quasi-orthogonals upstream
of the leading edge and downstream of the trailing edge but you can change these numbers if this seems
appropriate, simply by replying with n (n = “no”) to the prompt and then suggesting the new number of
quasi-orthogonals to be used. If you reply with a y (y= “yes”) then the automatic choice of the program is
used, which is fairly sensible in most cases.




      Note

      The limit on the number of points in each layer of the .rtzt files is 1000. The limit on the
      number of layers is 15. The maximum number of blade rows is 20. Up to 3000 quasi-orthogonals
      can be included in the final .geo file.



There are options to modify the number of quasi-orthogonals in the blade row and to change the orientation
of the calculating grid so that this is oriented in the positive z direction. The change in orientation is needed
because in some BladeGen files the flow travels in the direction of the negative z axis, and Vista TF assumes
that the flow is traveling in the direction of the positive x axis. Without this switch the hub and shroud
contours become reversed. The option to modify the number of quasi-orthogonals in a blade row has been

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                                                                                        Merging Several .rtzt Files into a Single .geo File

included so that RTZTtoGEO can better cope with axial blades with short chords relative to radial machines
with long chords. The program makes its own choice of the number of quasi-orthogonals needed, based
on the aspect ratio of the blade; this is more or less consistent with the stability requirements of the Vista
TF program. The rule used leads to 16 quasi-orthogonals in most radial compressors. You can change this
number if this seems appropriate, simply by replying with n (n = “no”) to the prompt and then suggesting
the new number of quasi-orthogonals to be used. If you reply with a y (y= “yes”) then the automatic choice
of the program is used, which is fairly sensible in most cases.



Merging Several .rtzt Files into a Single .geo File
Vista TF can run a computation for up to 20 blade rows. BladeGen can currently only be used to define the
blade rows individually so each .rtzt file contains only a single blade row. It is possible to merge these
into a single .geo file automatically using Vista RTZTtoGEO, as explained above. The procedure below de-
scribes how to merge individual .geo files by hand, just in case the automatic option fails.

 1.   Run RTZTtoGEO for the first blade row.
 2.   Set up a Vista TF calculation for this blade row with all the appropriate input files and get this to
      converge.
 3.   Run RTZTtoGEO for the next blade row.
 4.   Edit the .geo file of the first blade row to include the additional information for the downstream
      blade row, as follows:

      1.   Change the title section as appropriate (section 1).
      2.   Add new quasi-orthogonals in section 3 (copy from the .geo file of the next blade row and add
           to the .geo file of the first blade row). This may require modifications by hand in the duct region
           between the blade rows because the quasi-orthogonals have to step smoothly from inlet to outlet
           and not overlap. Usually this means deleting some quasi-orthogonals downstream of the first
           blade row and upstream of following blade row where the domains would overlap. Note that the
           numbering of the quasi-orthogonals does not have to be changed because the program does not
           read this information. The numbering of each quasi-orthogonal can then be left as originally
           output by the RTZTtoGEO program. Be careful in this process not to add any extra empty lines to
           the .geo file between the different lines or to take any away. Note that the type and orientation
           of the blade row should be correct automatically (with i_type 2 for stators and 3 for rotors) and
           that the number of upstream and downstream quasi-orthogonals can be modified so that this
           process is easier.
      3.   Do the same for the blade definition section (section 4), whereby only those lines within the blade
           row need to be copied in.
      4.   At the end of the .geo file, the details in section 5 need to be modified to give throat areas for
           the blade row that has been added (which is actually zero because the ,rtzt file does not provide
           this information. Thus if there are two blade rows each defined with five sections then there would
           be 10 lines at the end of the .geo file. These extra lines can also be cut and pasted from the
           .geo files for the appropriate blade row if you want.
      5.   Count the number of quasi-orthogonals that are left and change this in section 2. If you are lucky
           and have not had to delete any quasi-orthogonals, this is straightforward.

 5.   Edit the .cor file of the first blade row to include additional downstream blade row losses, deviation,
      and blockage data, noting that the location of the deviation is related to the number of the quasi-or-



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Vista TF

      thogonal and not the blade row. Note that the aerodynamic and control data files (.aer and .con)
      do not usually need to be changed in this process.
 6.   Delete the restart .rst file because the restart capability only works if there has been no change to
      the number of quasi-orthogonals. Vista TF recognizes this and recreates a new restart file automatically.
 7.   Run Vista TF, and repeat from step 3 for each additional blade row. Note that experienced users might
      manage to make the modifications to the .geo file and the .cor file for several blade rows together
      in 1 step, but doing it step-by-step gives better control of where any errors have been introduced.

Description of the RTZT File
This section describes the generic RTZT data file format for BladeGen. The file is an ASCII file that uses space
separation between values.

      Note

      Angular values must be in radians.

Example file:
 text enclosed in {} is a data item
 text enclosed in () is a comment
 text enclosed in [] is optional

 {number of blades}
 {number of splitters}   (0 is main blade only)
 (for each blade, main and splitter)
      {pitch fraction}   (Ignored for main blade)
      {number of layers}
      [N] [T]          (Normal or Tangential Thickness Flag)

                (for each layer)
                {span fraction} {number of points} [a][t][b]
                (for each point)

                {r} {theta} {z} {thickness}
                       :
                       :




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Index




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