COMPUTATIONAL FLUID DYNAMICS swen WHAT IS CFD COMPUTATIONAL

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COMPUTATIONAL FLUID DYNAMICS swen WHAT IS CFD COMPUTATIONAL Powered By Docstoc
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      WHAT IS CFD ?
COMPUTATIONAL FLUID DYNAMICS OR “CFD” IS
  THE ANALYSIS OF SYSTEMS INVOLVING FLUID
  FLOW , HEAT TRANSFER AND ASSOCIATED
  PHENOMINA SUCH AS CHEMICAL REACTIONS
  BY MEANS OF COMPUTER BASED NUMERICAL
  APPROACH .


IN THIS CFD APPROACH , THE EQUATIONS
  ( USUALLY PARTIAL DIFFERENTIAL EQUATIONS )
  THAT GOVERN A PROCESS OF INTEREST ARE
  SOLVED NUMERICALLY.
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    TYPES OF FLUID FLOWS

   VISCOUS OR INVISCID FLOWS

   INCOMPRESSIBLE OR COMPRESSIBLE FLOWS IN
    PIPES OR OPEN CHANNELS

   FLOWS IN PIPES AND TURBINES

   WATER WAVES

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HOW CAN A FLUID FLOW
PROBLEM BE ANALYSED?

EXPERIMENTAL

THEORETICAL

COMPUTATIONAL



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 COMPARISON OF APPROACHES
APPROACH       ADVANTAGES       DISADVANTAGES

               1. CAPABLE OF    1 .EQUIPMENT
                   BEING MOST   REQUIRED
                   REALISTIC    2 SCALING PROBLEMS
EXPERIMENTAL                    3 .TUNNEL CORRECTIONS
                                4. MEASUREMENT
                                   DIFFICULTIES
                                5. OPERATING COSTS

               1.CLEAN GENERAL 1.RESTRICTED TO SIMPLE
                 INFORMATION     GEOMETRY AND
                 WHICH IS        PHYSICS
THEORETICAL      USUALLY       2.USUALLY RESTRICTED
                 IN FORMULA       TO LINEAR PROBLEMS
                 FORM
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Start

Initial thinking                       conceptual mistake
about the problem
                                              no
Mesh generation                        poor mesh?
                      yes                     no
Flow specification                     incorrect flow specification
                      yes
Calculate numerical
Solution

Analyze results
                      results not ok
stop


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COMPARISON OF APPROACHES

   APPROACH        ADVANTAGES          DISADVANTAGES




                  1.NO RESTRICTION
                                     1.TRUNCATION
                    TO LINEARITY
                                        ERRORS
                 2.COMPLICATED
                    PHYSICS CAN
                                     2. ROUND OFF ERROR
 COMPUTATIONAL      BE TREATED.
                 3. TIME EVOLUTION
                     OF FLOW CAN
                     BE OBTAINED
                                     3.COMPUTER COSTS


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  NUMERICAL METHODS FOR FLUID
            FLOWS
Velocity and pressure
distribution by Nevier-
stokes equations and
equation of continuity

GOVERNING EQUATIONS
A 2D,laminar,
incompressible flow
with constant viscosity is
described by,
  X-momentum=(2u/  x2 +  2u/  y2) _  p/  x


  y-momentum=  ( 2v/  x2 +  2v/  y2) _  p/  y
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           BUILDING A MESH
BASIC PARTS FROM
 WHICH MESHES ARE
 BUILD:
   POINTS,SOMETIMES
    CALLED NODES.
   VOLUMES,ALSO KNOWN
    AS CELLS IN
     SOME DOCUMENTATION.
   ELEMENTS.

GEOMETRICALLY SPEAKING
  A MESH MAY BE 2D OR
  3D.SOME COMMON
  EXAMPLES ARE
  FOURNODEDQUADRILATER
  AL,FOUR
  NODEDTETRAHEDRON,
  SIX NODED PRISM          swen
BASIC APPROACH IN SOLVING A
PROBLEM BY CFD TECHNIQUE



                             GRID POINTS
                             (KNOWN TEMP.)

                             GRID POINTS
                             (UNKNOWN TEMP.)



IT IS A 4*4 GRID FOR COMPUTATION OF2D STEADY
STATE HEAT CONDUCTION IN A SQUARE PLATE
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MESH GENERATED AROUND AN AEROFOIL




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HOW DOES A CFD CODE WORKS


 ALL CODES CONTAIN THREE ELEMENTS



      A PRE-PROCESSOR

     A SOLVER

     A POST-PROCESSOR


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 HOW DOES A CFD WORKS

CFD CODES ARE STRUCTURED AROUND THE
 NUMERICAL ALGORITHMS


ALL COMMERCIAL CFD SOFTWARES SUCH AS
 FLUENT , CFX SOLUTIONS ETC , INCLUDE
 SOPHISTICATED USER INTERFACES TO INPUT
 PROBLEM PARAMETERS AND EXAMINE THE
 RESULTS


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        PRE-PROCESSOR :
DEFENITION OF GEOMETRY & REGION OF
 INTEREST: THE COMPUTATIONAL DOMAIN

GRID GENERATION THE SUBDIVISION OF THE
 DOMAIN INTO NUMBER OF SMALLER ,
 NON-OVERLAPPING SUBDOMAINS : GRID POINTS

SELECTION OF PHYSICAL AND CHEMICAL
 PHENOMENA THAT NEEDED TO BE MODELLED

DEFINATION OF FLUID PARTICLES

SPECIFICATION OF APPROPRIATE BOUNDARY
 CONDITIONS AT THE DOMAIN BOUNDARY
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        POST-PROCESSOR

POST PROCESSING MEANS ANALYSIS OF RESULTS



  THIS INCLUDES :

  VECTOR PLOTS

  LINE AND SHADED CONTOUR PLOTS

  2D AND 3D SURFACE PLOTS ETC


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          FLUENT

FLUENT IS A COMMERCIAL CFD SOFTWARE
 DEVELOPED IN „C‟ LANGUAGE

IT‟S A CONTROL VOLUME APPROACH

FLUENT IS THE BEST CFD TOOLFOR THE
 ANALYSIS OF FLOW AND HEAT TRANFER
 PROBLEMS ESPECIALLY IN PROCESS
 INDUSTRIES



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  ANALYSIS OF CFD OUTPUT DATA


CHECKING A SOLUTION

FLOW SHOULD LOOK QUALITATIVELY CORRECT
RESULTS SHOULD SHOW A VELOCITY CHANGE
THAT RESEMBLES THAT IN THE BOUNDARY LAYER
MASS CONSERVATION

REFINING A COMPUTER MODEL

INCREASE THE DENSITY OF MESH POINTS
IMPROVING THE PHYSICS OF THE MODEL

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SOME IMPORTANT APPLICATION
APPLICATION AREAS . . .
AERODYNAMICS OF AIRCRAFT AND VEHICLES:
 LIFT AND DRAG

HYDRODYNAMICS OF SHIPS

POWER PLANT : COMBUSTION IN IC ENGINES AND
 GAS TURBINES

TURBO MACHINERY : FLOW INSIDE ROTATING
 PASSAGES , DIFFUSERS ETC

ELECTRICAL AND ELECTRONIC ENGINEERING :
 COOLING OF EQUIPMENT INCLUDING MICROCIRCUIT
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       CONCLUSION

CFD MAKES MODELING PROCESS FASTER AND
 CHEAPER

INCREASES FLEXIBILITY IN DESIGN

MAY NOT BE A PERFECT SOLUTION ALWAYS




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                  QUESTIONS?




EXAMPLE FOR A HYBRID MESH
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THANK YOU




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