Automation of Cutter Suction Dredge

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					     Miedema, S.A., "A Numerical Method of Calculating the Dynamic Behaviour of Hydraulic Transport".
     21st Annual Meeting & Technical Conference of the Western Dredging Association, June 2001, Houston, USA 2001.




    A NUMERICAL METHOD OF CALCULATING THE DYNAMIC BEHAVIOUR OF HYDRAULIC
                                TRANSPORT.

                                                     S.A. Miedema1

                                                      ABSTRACT
The dynamic behavior of the hydraulic transport in a multi-pump/pipeline system is very complex. Usually the
stationary behavior is calculated, but due to varying mixture densities at the suction mouth and also varying soils, in
practice the behavior will be dynamical. Miedema (1996, 2001) already published about this subject before, but the
important phenomena have only been discussed globally.

The important phenomena for dynamical simulations are:
        The administrative problem of storing the mixture information for each pipeline segment
        The possibilities of longitudinal diffusion/separation.
        Inertial pressure
        Pump cavitation
        The dynamical behavior of a pump/drive system

To be able to determine the phenomena that occur in the pipeline as a function of the position in the pipeline, it is
necessary to store the information required to determine these phenomena. The most important information required
is the physical contents at each pipeline position. The pipeline is divided in segments.

Since the dynamic behavior is governed by a number of non-linear phenomena, the simulation of the dynamic
behavior is carried out in the time-domain, using a time step of about 0.1 second. The length of a pipeline segment is
determined by multiplying the line velocity with the time step. In general this results in a segment length of about 0.5
m. For a pipeline system length of 4000 m, this results in 8000 segments. Since the segments move through the
system, every time step this requires a lot of administration.

In the current version of the simulation software, there is no longitudinal diffusion between the segments. This is
however required to describe phenomena like bed load.

A steady state process requires a constant density and solids properties in the system and thus at the suction mouth. In
practice it is known, that the solids properties and the density change with respect to time. As a result, the pump
discharge pressure and vacuum will change with respect to time and the pipeline resistance will change with respect
to time and place. A change of the discharge pressure will result in a change of the torque on the axis of the pump
drive on one hand and in a change of the flow velocity on the other hand. The mixture in the pipeline has to
accelerate or decelerate. Since centrifugal pumps respond to a change in density and solids properties at the moment
the mixture passes the pump, while the pipeline resistance is determined by the contents of the pipeline as a whole,
this forms a complex dynamic system. The inertial pressure of the mixture has to be added to the resistance of the
mixture. In fact, the inertial pressure is always equal to the difference between the total pressure generated by the
pumps and the total resistance of the mixture in the pipeline system. If this difference is positive (the pump pressure
has increased due to an increase of the mixture density), the mixture will accelerate. If negative, the mixture will
decelerate.

As a result of the acceleration and deceleration, the mixture velocity (line velocity) will vary as a function of time. To
realize a stable dredging process, it is required to have a line velocity that will not vary too much. The line velocity
can be controlled by varying the revolutions of one of the dredge pumps, where the last pump is preferred.

Keywords: Automation, Hydraulic Transport, Flow Control, Dynamic Modeling


1Associate Professor, Chair of Dredging Technology, Delft University of Technology, Mekelweg 2, 2628 AK Delft,
Netherlands, Tel.: +31-15-2788359, Fax: +31-15-2781397; Email: S.A.Miedema@WbMT.TUDelft.NL; Homepage:
http://www-ocp.wbmt.tudelft.nl/dredging/miedema/MIEDEMA.HTM




Copyright: Dr.ir. S.A. Miedema
     Miedema, S.A., "A Numerical Method of Calculating the Dynamic Behaviour of Hydraulic Transport".
     21st Annual Meeting & Technical Conference of the Western Dredging Association, June 2001, Houston, USA 2001.




                                                      INTRODUCTION

A multi pump/pipeline system consists of components with different dynamic behavior. To model such a system, one
should start with simple mathematical descriptions of the sub-systems, to be able to determine the sensitivity of the
behavior of the system to changes in one of the sub-systems. Miedema (1995, 2001) as well as many authors
described the hydraulic system in detail. In this paper the system will be described globally, while the phenomena are
described in detail. The following sub-systems can be distinguished:
         - The sand/water slurry in the pipeline
         - The centrifugal pump
         - The pump drive
         - Flow control (optional)
When clear water flows through the pipeline, the pressure loss can be determined with the well-known Darcy-
Weisbach equation:

                           L 1
             ∆p w = λ ⋅     ⋅ ⋅ ρw ⋅ c2                                                                               (1)
                           D 2
For the determination of the pressure losses of a heterogeneous flow many theories are available, like
Durand/Condolios/Gibert, Fuhrboter, Jufin/Lopatin and Wilson. In this paper the Durand/Condolios/Gibert theory
will be used, further referred to as the Durand theory. Durand assumes that the clear water resistance in a pipeline
should be multiplied by a factor depending on the line speed, the grain size distribution and the concentration,
according to:

                                                  n
            ∆p m = ∆p w ⋅ (1 + Φ ⋅ C t ) + ∑ ξ n ⋅ 1 ⋅ ρ m ⋅ c 2 + ρ m ⋅ g ⋅ H g + ρ m ⋅ L ⋅ c
                                                   2                                                                  (2)
                                                  1


In which:

                                             −3 / 2
                        c2         
                        g ⋅ D ⋅ Cx 
             Φ = 180 ⋅                                                                                              (3)
                                   

And:

                     g⋅d
             Cx =                                                                                                     (4)
                     v2
When the flow decreases, there will be a moment where sedimentation of the grains starts to occur. The
corresponding line speed is called the critical velocity. Although in literature researchers do not agree on the
formulation of the critical velocity, the value of the critical velocity is often derived by differentiating Equation 2
with respect to the line speed c and taking the value of c where the derivative equals zero. This gives:


                     g ⋅ D p ⋅ (90 ⋅ C t )
                                         2/3

            c cr =                                                                                                   (5)
                                 Cx

At line speeds less then the critical velocity, sedimentation occurs and part of the cross-section of the pipe is filled
with sand, resulting in a higher flow velocity above the sediment. Durand assumes equilibrium between
sedimentation and scour, resulting in a Froude number equal to the Froude number at the critical velocity.




                                                              1
Copyright: Dr.ir. S.A. Miedema
     Miedema, S.A., "A Numerical Method of Calculating the Dynamic Behaviour of Hydraulic Transport".
     21st Annual Meeting & Technical Conference of the Western Dredging Association, June 2001, Houston, USA 2001.




                       c cr            (90 ⋅ C t )2 / 3
           Frcr =                =                                                                                    (6)
                      g ⋅ Dp                  Cx

By using the hydraulic diameter concept, at lines speeds less then the critical velocity, the resistance can be
determined.

The behavior of centrifugal pumps can be described with the Euler impulse moment equation:

                                       Q ⋅ cot(β o )                      Q ⋅ cot(β i ) 
             ∆p E = ρ f ⋅ u o ⋅  u o −                − ρf ⋅ u i ⋅  u i −
                                                                                                                     (7)
                                
                                        2 ⋅ π ⋅ ro  
                                                                             2 ⋅ π ⋅ ri  

For a known pump this can be simplified to:

              ∆p E = ρ f ⋅ (C1 − C 2 ⋅ Q )                                                                             (8)

Because of incongruity of impeller blades and flow, the finite number of blades, the blade thickness and the internal
friction of the fluid, the Euler pressure ∆p E has to be corrected with a factor k, with a value of about 0.8. This factor
however does not influence the efficiency. The resulting equation has to be corrected for losses from frictional
contact with the walls and deflection and diversion in the pump and a correction for inlet and impact losses. The
pressure reduction for the frictional losses is:

               ∆p h .f . = C 3 ⋅ ρ f ⋅ Q 2                                                                             (9)

For a given design flow Qd the impact losses can be described with:

               ∆p h .i . = C 4 ⋅ ρ f ⋅ (Q d − Q )
                                                    2
                                                                                                                      (10)

The total head of the pump as a function of the flow is now:

                                                                (
               ∆p p = k ⋅ ∆p E − ∆p h .f . − ∆p h .i . = ρ f ⋅ k ⋅ (C1 − C 2 ⋅ Q ) − C 3 ⋅ Q 2 − C 4 ⋅ (Q d − Q )
                                                                                                                2
                                                                                                                      (11)


This is a second-degree polynomial in Q. The fluid density              ρ f in the pump can be either the density of a
homogeneous fluid (for water         ρ w ) or the density of a mixture ρ m passing the pump.

If a mixture is pumped however, the pump head increases because of the mixture density as has been pointed out
when discussing equation 11 and the pump efficiency decreases because a heterogeneous mixture is flowing through
the pump. The decrease of the efficiency depends upon the average grain diameter, the impeller diameter and the
solids concentration and can be determined with (according to Stepanoff):

          η m = (1 − C t ⋅ (0.466 + 0.4 ⋅ Log10(d 50 ))/ D )                                                         (12)

Pump drives used in dredging are diesel direct drives, diesel/electric drives and diesel/hydraulic drives. In this paper
the diesel direct drive, as the most common arrangement, is considered.

At nominal operating speed, the maximum load coincides with the nominal full torque point. If the torque is less then
the nominal full torque, the engine speed usually rises slightly as the torque decreases. This is the result of the control
of the speed by the governor. The extent of this depends upon the type of governor fitted.




                                                                2
Copyright: Dr.ir. S.A. Miedema
     Miedema, S.A., "A Numerical Method of Calculating the Dynamic Behaviour of Hydraulic Transport".
     21st Annual Meeting & Technical Conference of the Western Dredging Association, June 2001, Houston, USA 2001.




If the engine load increases above the full torque point, the speed decreases and the engine operates in the full fuel
range. With most diesel engines the torque will increase slightly as the speed decreases, because of a slightly
increasing efficiency of the fuel pumps. When the load increases further, insufficient air is available to produce
complete combustion and the engine stalls. The torque drops rapidly and heavily polluted gasses are emitted. The
smoke limit has been reached. The speed range between the full torque point and the smoke limit is often referred to
as the constant torque range.

The torque/speed characteristic of the diesel engine can thus be approximated by a constant full torque upon the
nominal operating speed, followed by a quick decrease of the torque in the governor range. This characteristic
however is valid for a steady state process of the diesel engine. When the speed of the diesel changes, the load will
change, but also the inertia effects of the diesel have to be taken into account. The equation of motion of the diesel
engine, gearbox and centrifugal pump combination, reduced to the axis of the centrifugal pump, is:

           (I   d .e .   + I g.b. + I c.p. )⋅ ϕ = Td .e. − Th .t . = K p ⋅ (ϕ s.p. − ϕ)                               (13)

The solution of this first order system is:

                                                 (
             ϕ = ϕ 0 + (ϕ s . p . − ϕ 0 )⋅ 1 − e − t / τd . e .   )                                                   (14)


In which   ϕ 0 is the angular velocity at an arbitrary time, defined as t=0. Using time domain calculations with a time
step ∆t , the angular velocity at time step n can now be written as a function of the angular velocity at time step n-1
and the set point angular velocity           ϕ s .p . according to:

                                                         (
                ϕ n = ϕ n −1 + (ϕ s . p . − ϕ n −1 )⋅ 1 − e − ∆t / τd . e .   )                                       (15)


Equation 16 is used to simulate flow control. If the factor γ is chosen to high, the system is fast but tends to oscillate.
If this factor is to small, the system responds very slowly. In the simulation a value of 2 is used.

                                                                       c −c
                n f .c . = n + n ⋅ 1 ⋅ (γ + 1) ⋅ ε ⋅ (ε + 2) With: ε =  f .c .
                                   2                                                                                 (16)
                                                                        c 

These basic equations describe the pump/pipeline system. The next paragraphs describe the phenomena that occur.


                                          THE PUMP /PIPELINE SYSTEM DESCRIPTION

For this paper, a system is defined consisting of a suction line followed by three pump/pipeline units (see Fig. 1). The
first pump is a ladder pump, with a speed of 200 rpm, an impeller diameter of 1.5 m and 1050 kW on the axis. The
second and the third pump run also at a speed of 200 rpm, have an impeller diameter of 2.4 m and 3250 kW on the
axis. The time constants of all three pumps are set to 4 seconds. The time constant of the density meter is set to 10
seconds. The suction line starts at 10 m below water level, has a length of 12 m and a diameter of 0.69 m. The ladder
pump is placed 5 m below water level. The main pump and the booster pump are placed 10 m above water level. The
pipeline length between ladder and main pump is 30 m, between main pump and booster pump 2000 m, as is the
length of the discharge line. The pipe diameters after the ladder pump are 0.61 m. Sand is used with a d15 of 0.25
mm, a d50 of 0.50 mm and a d85 of 0.75 mm.
 In a steady state situation, the revolutions of the pumps are fixed, the line speed is constant and the solids properties
and concentration are constant in the pipeline. The working point of the system is the intersection point of the pump
head curve and the pipeline resistance curve. The pump curve is a summation of the head curves of each pump
according to Equation 11. The resistance curve is a summation of the resistances of the pipe segments and the




                                                                              3
Copyright: Dr.ir. S.A. Miedema
     Miedema, S.A., "A Numerical Method of Calculating the Dynamic Behaviour of Hydraulic Transport".
     21st Annual Meeting & Technical Conference of the Western Dredging Association, June 2001, Houston, USA 2001.




geodetic head according to Equation 2. Figure 2 shows this steady state situation for the system used, at 6 densities
ranging from clear water up to a density of 1.6 ton/m3.




                                                                              Figure 1: The pump/pipeline system used.
                                                Stationary Pump Behaviour Windows V4.01 - Torque Limited:                                             6000                                                         12000
                                                                                                                                                                                               Total Power in kW
                                                                                                                                  Prod. in m^3/hour




                                                                  12-29-2000 - 04:35:28
                                                                                                                                                      4800                                                         9600
                                                C:\PROGRA~1\CSDPRO~1\PIPELINE\PIPELI~1.DAT in Default
                                                                                                                                                      3600                                                         7200

                                 4700                                                                                                                 2400                                                         4800
                                                                                                                                                      1200                                                         2400
                                 4230
                                                                                                                                                        0                                                             0
                                                                                                                                                             1.0   1.2 1.4 1.6 1.8       2.0                               1.0   1.2 1.4 1.6 1.8       2.0
                                 3760
                                                                                                                                                                   Density in ton/m^3                                            Density in ton/m^3
                                 3290
                                                                                                                                                      4.00
                                                                                                                                  Flow in m^3/sec
             Total Head in kPa




                                 2820                                                                                                                 3.20
                                                                                                                                                      2.40
                                 2350                                                                                                                 1.60
                                                                                                                                                      0.80
                                 1880                                                                                                                 0.00
                                                                                                                                                             0     1000 2000 3000 4000 5000 6000 7000 8000 9000 10000
                                 1410
                                                                                                                                                                              Length of discharge line in m
                                 940
                                                                                                                                                      6000
                                                                                                                                  Prod. in m^3/hour




                                 470                                                                                                                  4800
                                                                                                                                                      3600
                                    0                                                                                                                 2400
                                        0.00   0.40    0.80   1.20     1.60 2.00 2.40            2.80   3.20     3.60    4.00                         1200
                                                                        Flow in m^3/sec                                                                  0
                                                                                                                                                             0     1000 2000 3000 4000 5000 6000 7000 8000 9000 10000
                                  Vcrit        Water      Rho: 1.144   Rho: 1.258   Rho: 1.372     Rho: 1.486    Rho: 1.600
                                                                                                                                                                              Length of discharge line in m

                                 1900
             Pressure in kPa




                                 1500
                                 1100
                                 700
                                 300
                                 -100
                                          0             410              820               1230                 1640           2050           2460                                2870                             3280              3690             4100
                                                                                                                 Distance from suction mouth in m


                                                                Figure 2: Characteristics of the pump/pipeline system.

                                                                                        THE SEGMENTED PIPELINE

In reality, the solids properties and concentration are not constant in time at the suction mouth. As a result of this, the
solids properties and concentration are not constant as a function of the position in the pipeline. To be able to know




                                                                                                                              4
Copyright: Dr.ir. S.A. Miedema
     Miedema, S.A., "A Numerical Method of Calculating the Dynamic Behaviour of Hydraulic Transport".
     21st Annual Meeting & Technical Conference of the Western Dredging Association, June 2001, Houston, USA 2001.




these properties as a function of the position in the pipeline, the pipeline must be divided into small segments. These
segments move through the pipeline with the line speed. Each time step a new segment is added at the suction mouth,
while part of the last segment leaves the pipeline. Because the line speed is not constant, the length of the segment
added is not constant, but equals the line speed times the time step. For each segment the resistance is determined, so
the resistance as a function of the position in the pipeline is known. This way also the vacuum and the discharge
pressure can be determined for each pump. If vacuum results in cavitation of one of the pumps, the pump head is
decreased by decreasing the pump density, depending on the time the pump is cavitating.

As mentioned before, each segment contains the mixture properties. The two most important properties are the
mixture density and the grain size distribution. If a homogeneous transport model is considered, the grain distribution
can be replaced by the characteristic factor according to Equation 4. For a heterogeneous or two-phase transport
model, the problem becomes much more complicated.

The segments move through the pipeline with the line speed, assuming that all of the contents of a segment move at
the same speed. However if part of the mixture has settled at the bottom of the pipeline, this part will move with a
much smaller velocity then the average velocity, while the mixture above the sediment will move with a velocity
higher then the average. In a stationary situation this does not matter, as long as the transport model used takes this
into account (the Durand model takes this into account), but in a non-stationary situation there may be temporary
accumulation of solids. Also dunes may occur, moving through the pipeline. To implement these phenomena a
longitudinal diffusion model has to be developed. The current administrative system in the simulation software is
suitable for storing the information required to describe these phenomena. However the information stored has to be
extended, since two-phase flow requires storage of two components, the bed load and the suspended material.
With a time step in the simulation software of 0.1 to 0.2 seconds, the segment length varies (with a line speed of 5
m/s) from 0.5 to 1.0 m. The required length for a good description of dunes moving through the pipeline is unknown,
but from experiments in our laboratory it seems a segment length of 0.5 m is still to high. An intuitive estimate of 0.1
to 0.2 m seems reasonable. The Durand model however has not been developed for a pipeline of only 0.1 m.

The mass conservation equation of a pipe segment can be described with Equation 17. In this equation all terms give
a mass flow. The sum of the mass flow of the suspended material and the bed load that enter a segment, should be
equal to the sum of the suspended material and the bed load that leave the segment plus the material that settles in the
segment. The last term on the right hand side is the settlement of suspended material into the bed. This term is
positive when material settles (accumulates) in the segment.

             Qin −s + Qin − b = Qout −s + Qout − b + Qs→ b                                                               (17)



Q                          Suspended                                                                             Q
     in −s                                                          Q    s→b
                                                                                                                     out−s



Q    in −b
                           Bed load                                                                                  Q
                                                                                                                     out−b

                                         Pipe segment
                                   Figure 3: The mass equilibrium in a pipe segment.

The question is however; whether for a good description of the transport it suffices to administer the suspended load
and the bed load in one segment moving through the pipeline. In fact the velocity of the suspended load will be
higher then the average line speed and the velocity of the bed will be much smaller. The pipe segment should have to
be split into two separate segments for the suspended load and for the bed load, moving at two different velocities
through the system, in order to administer the two phase flow correctly. The current method of administering the
contents of the segments is suitable for suspended load only at line speeds above the critical velocity.




                                                             5
Copyright: Dr.ir. S.A. Miedema
     Miedema, S.A., "A Numerical Method of Calculating the Dynamic Behaviour of Hydraulic Transport".
     21st Annual Meeting & Technical Conference of the Western Dredging Association, June 2001, Houston, USA 2001.




A good description of the vertical diffusion between the suspended load and the bed load is not yet available and will
be subject for further research. Erosion diffusion equations are used for hopper sedimentation as well, but these
equation do not suffice Miedema and Vlasblom 1996.

                                                    THE INERTIAL EFFECTS IN THE PIPELINE

A steady state process requires a constant density and solids properties in the system and thus at the suction mouth. In
practice it is known, that the solids properties and the density change with respect to time. As a result, the pump
discharge pressure and vacuum will change with respect to time and the pipeline resistance will change with respect
to time and place. A change of the discharge pressure will result in a change of the torque on the axis of the pump
drive on one hand and in a change of the flow velocity on the other hand. The mixture in the pipeline has to
accelerate or decelerate. Since centrifugal pumps respond to a change in density and solids properties at the moment
the mixture passes the pump, while the pipeline resistance is determined by the contents of the pipeline as a whole,
this forms a complex dynamic system.


                                             Stationary Pump Behaviour Windows V4.01 - Not Limited
                                                              05-07-2001 - 08:23:50
                                              c:\samcons\spbw\pipeline\pipeline.inp in Default Sand

                                   4700

                                   4230
                                                                                                  5 4
                                   3760
                                                                                              7
                                   3290
                                                                                            6 3 2
               Total Head in kPa




                                   2820

                                   2350                                                      1
                                   1880

                                   1410

                                   940

                                   470

                                     0
                                      0.00 0.40 0.80 1.20 1.60 2.00 2.40 2.80 3.20 3.60 4.00
                                                          Flow in m^3/sec
                                          Vcrit                 Case 1            Case 2              Case 3



                                                  Figure 4: The system curves for 3 cases, accelerating.
The inertial pressure of the mixture has to be added to the resistance of the mixture. In fact, the inertial pressure is
always equal to the difference between the total pressure generated by the pumps and the total resistance of the
mixture in the pipeline system. If this difference is positive (the pump pressure has increased due to an increase of the
mixture density), the mixture will accelerate. If negative, the mixture will decelerate.
As a result of the acceleration and deceleration, the mixture velocity (line velocity) will vary as a function of time. To
realize a stable dredging process, it is required to have a line velocity that will not vary too much. The line velocity
can be controlled by varying the revolutions of one of the dredge pumps, where the last pump is preferred.




                                                                            6
Copyright: Dr.ir. S.A. Miedema
     Miedema, S.A., "A Numerical Method of Calculating the Dynamic Behaviour of Hydraulic Transport".
     21st Annual Meeting & Technical Conference of the Western Dredging Association, June 2001, Houston, USA 2001.




From the above one can distinguish the different effect by the time they require to change/occur:
              1.                   Very fast (within a second), the change in discharge pressure of a centrifugal pump
              2.                   Fast (seconds), the change in revolutions of the pump drive and the change in line speed
                                   (acceleration and deceleration)
              3.                   Slow (minutes), filling up the pipeline with mixture or a change in mixture content

These effects can also be recognized in the equations describing the pump curve and the system curve. Equation 11
shows the effect of the fluid (mixture) density on the discharge pressure. Equation 14 shows the effect of a changing
set point of the pump drive. Equation 2 contains the inertial effect in the most right term on the right hand side, while
the effect of the changing mixture contents is described by the first term on the right hand side. Figure 2 shows the
system curves and the pump curves for the system described in Figure 1, for 6 different densities, including clear
water, for a stationary situation. The intersection points of each system and pump curve at one density are the
working points for the system at that specific density.


                                             Stationary Pump Behaviour Windows V4.01 - Not Limited
                                                              05-07-2001 - 08:23:50
                                              c:\samcons\spbw\pipeline\pipeline.inp in Default Sand

                                   4700

                                   4230
                                                                                                 1
                                   3760
                                                                                            2 36
                                   3290
               Total Head in kPa




                                   2820                                                          7
                                   2350
                                                                                           4 5

                                   1880

                                   1410

                                    940

                                    470

                                       0
                                        0.00 0.40 0.80 1.20 1.60 2.00 2.40 2.80 3.20 3.60 4.00
                                                            Flow in m^3/sec
                                          Vcrit                 Case 1            Case 2              Case 3



                                                  Figure 5: The system curves for 3 cases, decelerating.
Figure 4 is a representation of a number of phenomena that occur subsequently when the system (Figure 1) filled with
water, is filled with mixture with a density of 1.6 ton/m3. In this figure case 1 represents the system and the pump
curve for the system filled with water. Case 2 represents the system with the pipeline filled with mixture up to a point
just before the 3rd (booster) pump. Case 3 represents the system filled entirely with the mixture.

Now, what happens if a system filled with water is continuously filled with the mixture?

First the working point is point 1 in Figure 3. This is the intersection point of the pump and system curves for water.
When mixture enters the system, within a few (about 8) seconds the mixture has reached the ladder and main pump,




                                                                            7
Copyright: Dr.ir. S.A. Miedema
     Miedema, S.A., "A Numerical Method of Calculating the Dynamic Behaviour of Hydraulic Transport".
     21st Annual Meeting & Technical Conference of the Western Dredging Association, June 2001, Houston, USA 2001.




since the distance is only about 44 m and the line speed about 5 m/sec. At that moment, the discharge pressure of the
ladder pump and main pump increase proportionally to the mixture density, resulting in a pump curve according to
case 2 and a working point 2. The flow and thus the line speed will not change instantly because of the inertia of the
fluid and solids mass in the pipeline. Number 6 shows the access pressure caused by the sudden increase of the
discharge pressure. This access pressure has to take care of the acceleration of the pipeline contents. This
acceleration will take in the order of 10-20 seconds.

The filling of the system continues and the resistance of the mixture slowly increases, so the working point moves
from point 2 to point 3. With the line speed of 5 m/s, this will take about 400 seconds or almost 7 minutes. When the
mixture reaches the booster pump, at once the discharge pressure increases, resulting in the pump curve according to
case 3, the top curve. The working point will move to point 4, while 7 represents the access pressure causing the
acceleration of the pipeline contents. Moving from 3 to 4 will take 10-20 seconds. When the pipeline continues to be
filled with mixture, the resistance increases, resulting in the working point moving from 4 to 5 in about 400 seconds.

Figure 4 shows the same procedure for a pipeline filled with a mixture of density 1.6 ton/m3. In this case the pipeline,
containing mixture of 1.6 ton/m3, is filled with water, resulting in decreasing discharge pressures and pipeline
resistance. The procedure is almost the inverse, but Figure 5 shows that the path followed is different. In working
point 1, all the pumps and the pipeline are filled with the mixture. When the water reaches the ladder and main pump,
the pump curve is decreased to case 2 and the new working point is point 2. 6 gives the deceleration pressure, so the
contents of the pipeline will decelerate from 1 to 2 in about 10-20 seconds. From 2-3 the pipeline is filled with water
up to the booster pump, resulting in a decrease of the resistance, taking about 400 seconds. When the water reaches
the booster pump, the pump curve decreases again to case 1, resulting in working point 4. Again it takes 10-20
seconds to move from point 3 to point 4. At last the pipeline behind the booster pump is filled with water, resulting in
a decrease of the resistance, taking about 400 seconds. The final working point is point 5. Both Figures 4 and 5 give
an example of the non-stationary effects in a multi-pump/pipeline system.

                                        CONCLUSIONS AND DISCUSSION

Multi pump/pipeline systems can be configured in an infinite number of configurations. Phenomena that occur in one
configuration do not have to occur in other configurations. So the configuration to carry out simulations to examine
certain phenomena has to be chosen carefully. The configuration used in this paper is suitable for simulation of most
phenomena. The examples show, that moving from one working point to the next working point, does not occur
instantaneously, but with a time delay, where the time delay depends on the phenomena.

The simulation model used is very well suitable for fully suspended load, but has a deficiency for two phase flow.
The main shortcoming is the fact that suspended load and bed load move through the system at two different
velocities, not being equal to the average line speed.

A second shortcoming is the lack of availability of a good model for the vertical diffusion between the suspended
load and the bed load. This will be subject for further research.



                                                     LITERATURE

Bree, S.E.M. de 1977, "Centrifugal Dredgepumps". IHC Holland 1977.
Gibert, R., "Transport Hydraulique et Refoulement des Mixtures en Conduites".
Huisman, L. 1995, "Sedimentation and Flotation". Lecture Notes, Delft University Of Technology 1973-1995.

Miedema, S.A. & Vlasblom, W.J., "Theory for Hopper Sedimentation". 29th Annual Texas A&M Dredging Seminar.
New Orleans, June 1996.
Miedema, S.A. 1996, "Modeling and Simulation of the Dynamic Behavior of a Pump/Pipeline System". 17th Annual
       Meeting & Technical Conference of the Western Dredging Association. New Orleans, June 1996.




                                                             8
Copyright: Dr.ir. S.A. Miedema
        Miedema, S.A., "A Numerical Method of Calculating the Dynamic Behaviour of Hydraulic Transport".
        21st Annual Meeting & Technical Conference of the Western Dredging Association, June 2001, Houston, USA 2001.




Miedema, S.A. 2000, "Dynamic Pump Behaviour Windows V4.01". Software, Delft 2000.
Miedema, S.A., "Automation of a Cutter Dredge, Applied to the Dynamic Behaviour of a Pump/Pipeline System".
       Proc. WODCON VI, April 2001, Kuala Lumpur, Malaysia 2001.
Wilson, K.C. & Addie, G.R. & Clift, R. 1992, "Slurry Transport Using Centrifugal Pumps". Elsevier Science
        Publishers Ltd. 1992.


                                                     NOMENCLATURE

Symbol           Description                           Unit                   Index        Description
c                Line speed                            m/sec                  c            Concentration
C1,2,3,4         Coefficients                          -                      cr           Critical
Cd               Drag coefficient                      -                      c.p.         Centrifugal pump
Ct               Transport concentration                                      d            Design
Cv               Volumetric concentration              -                      d.e.         Diesel engine
Cx               Drag coefficient                      -                      d.f.         Dry friction
d                Grain diameter                        m                      D            Diameter
D                Impeller diameter                     m                      f            Fluid
D                Pipe diameter                         m                      g            Geodetic
Fr               Froude number                         -                      gr           Grain
g                Gravitational constant                m/sec2                 g.b.         Gear box
H                Height                                m                      h.f.         Hydraulic friction
I                Mass moment of inertia                ton⋅m3                 h.i.         Hydraulic impact
k                Constant                              -                      h.p.         Hydraulic power
Kp               Proportionality constant              kNms/rad               h.t.         Hydraulic transport
L                Length of pipeline                    m                      i            In
n                Revolutions                           rpm                    m            Mixture
p                Pressure                              kPa                    m            Measured
P                Power                                 kW                     n            Revolutions
Q                Flow                                  m3/sec                 o            Out
Qin-s            Mass flow into segment                ton/m3
                 suspended
Qin-b            Mass flow into segment bed            ton/m3
                 load
Qout-s           Mass flow out of segment              ton/m3
                 suspended
Qout-b           Mass flow out of segment bed          ton/m3
                 load
Qs→b             Mass flow from suspended load         ton/m3
                 to bed load
r                Radius                                m                      p            Proportional
Re               Reynolds number                       -                      p            Pump
T                Torque                                kNm                    p            Pipe
u                Tangential velocity                   m/sec                  q            Quarts
v                Settling velocity grains              m/sec                  s.p.         Set point
α,β              Coefficients                          -                      t.           Total
β                Impellar blade angle                  rad                    w            Water
ε                Wall roughness                        m                      0            Initial value (boundary
                                                                                           condition)
ε                Ratio                                 -                      n            Number of time step
Φ                Durand coefficient                    -                      E            Euler
η                Efficiency                            -                      15           %
ϕ                Rotation angle of centrifugal         rad                    50           %
                 pump




                                                                9
Copyright: Dr.ir. S.A. Miedema
     Miedema, S.A., "A Numerical Method of Calculating the Dynamic Behaviour of Hydraulic Transport".
     21st Annual Meeting & Technical Conference of the Western Dredging Association, June 2001, Houston, USA 2001.




ϕ              Angular velocity of centrifugal      rad/sec                85           %
               pump
ϕ              Angular acceleration of              rad/sec2               15           %
               centrifugal pump
λ              Friction coefficient                 -                      50           %
ν              Kinematic viscosity                  m2/sec                 85           %
ρ              Density                              ton/m3
τ              Time constant                        sec
ξ              Friction coefficient                 -
ψ              Shape factor                         -




                                                              10
Copyright: Dr.ir. S.A. Miedema
     Miedema, S.A., "A Numerical Method of Calculating the Dynamic Behaviour of Hydraulic Transport".
     21st Annual Meeting & Technical Conference of the Western Dredging Association, June 2001, Houston, USA 2001.




                    Bibliography Dr.ir. S.A. Miedema 1980-2010
    1. Koert, P. & Miedema, S.A., "Report on the field excursion to the USA April 1981"
        (PDF in Dutch 27.2 MB). Delft University of Technology, 1981, 48 pages.
    2. Miedema, S.A., "The flow of dredged slurry in and out hoppers and the settlement
        process in hoppers" (PDF in Dutch 37 MB). ScO/81/105, Delft University of
        Technology, 1981, 147 pages.
    3. Miedema, S.A., "The soil reaction forces on a crown cutterhead on a swell
        compensated ladder" (PDF in Dutch 19 MB). LaO/81/97, Delft University of
        Technology, 1981, 36 pages.
    4. Miedema, S.A., "Computer program for the determination of the reaction forces on a
        cutterhead, resulting from the motions of the cutterhead" (PDF in Dutch 11 MB).
        Delft Hydraulics, 1981, 82 pages.
    5. Miedema, S.A. "The mathematical modeling of the soil reaction forces on a
        cutterhead and the development of the computer program DREDMO" (PDF in Dutch
        25 MB). CO/82/125, Delft University of Technology, 1982, with appendices 600
        pages.
    6. Miedema, S.A.,"The Interaction between Cutterhead and Soil at Sea" (In Dutch).
        Proc. Dredging Day November 19th, Delft University of Technology 1982.
    7. Miedema, S.A., "A comparison of an underwater centrifugal pump and an ejector
        pump" (PDF in Dutch 3.2 MB). Delft University of Technology, 1982, 18 pages.
    8. Miedema, S.A., "Computer simulation of Dredging Vessels" (In Dutch). De
        Ingenieur, Dec. 1983. (Kivi/Misset).
    9. Koning, J. de, Miedema, S.A., & Zwartbol, A., "Soil/Cutterhead Interaction under
        Wave Conditions (Adobe Acrobat PDF-File 1 MB)". Proc. WODCON X, Singapore
        1983.
    10. Miedema, S.A. "Basic design of a swell compensated cutter suction dredge with axial
        and radial compensation on the cutterhead" (PDF in Dutch 20 MB). CO/82/134, Delft
        University of Technology, 1983, 64 pages.
    11. Miedema, S.A., "Design of a seagoing cutter suction dredge with a swell compensated
        ladder" (PDF in Dutch 27 MB). IO/83/107, Delft University of Technology, 1983, 51
        pages.
    12. Miedema, S.A., "Mathematical Modeling of a Seagoing Cutter Suction Dredge" (In
        Dutch). Published: The Hague, 18-9-1984, KIVI Lectures, Section Under Water
        Technology.
    13. Miedema, S.A., "The Cutting of Densely Compacted Sand under Water (Adobe
        Acrobat PDF-File 575 kB)". Terra et Aqua No. 28, October 1984 pp. 4-10.
    14. Miedema, S.A., "Longitudinal and Transverse Swell Compensation of a Cutter
        Suction Dredge" (In Dutch). Proc. Dredging Day November 9th 1984, Delft
        University of Technology 1984.
    15. Miedema, S.A., "Compensation of Velocity Variations". Patent application no.
        8403418, Hydromeer B.V. Oosterhout, 1984.
    16. Miedema, S.A., "Mathematical Modeling of the Cutting of Densely Compacted Sand
        Under Water". Dredging & Port Construction, July 1985, pp. 22-26.
    17. Miedema, S.A., "Derivation of the Differential Equation for Sand Pore Pressures".
        Dredging & Port Construction, September 1985, pp. 35.
    18. Miedema, S.A., "The Application of a Cutting Theory on a Dredging Wheel (Adobe
        Acrobat 4.0 PDF-File 745 kB)". Proc. WODCON XI, Brighton 1986.
    19. Miedema, S.A., "Underwater Soil Cutting: a Study in Continuity". Dredging & Port
        Construction, June 1986, pp. 47-53.



Copyright: Dr.ir. S.A. Miedema
     Miedema, S.A., "A Numerical Method of Calculating the Dynamic Behaviour of Hydraulic Transport".
     21st Annual Meeting & Technical Conference of the Western Dredging Association, June 2001, Houston, USA 2001.




    20. Miedema, S.A., "The cutting of water saturated sand, laboratory research" (In Dutch).
        Delft University of Technology, 1986, 17 pages.
    21. Miedema, S.A., "The forces on a trenching wheel, a feasibility study" (In Dutch).
        Delft, 1986, 57 pages + software.
    22. Miedema, S.A., "The translation and restructuring of the computer program
        DREDMO from ALGOL to FORTRAN" (In Dutch). Delft Hydraulics, 1986, 150
        pages + software.
    23. Miedema, S.A., "Calculation of the Cutting Forces when Cutting Water Saturated
        Sand (Adobe Acrobat 4.0 PDF-File 16 MB)". Basic Theory and Applications for 3-D
        Blade Movements and Periodically Varying Velocities for, in Dredging Commonly
        used Excavating Means. Ph.D. Thesis, Delft University of Technology, September
        15th 1987.
    24. Bakker, A. & Miedema, S.A., "The Specific Energy of the Dredging Process of a
        Grab Dredge". Delft University of Technology, 1988, 30 pages.
    25. Miedema, S.A., "On the Cutting Forces in Saturated Sand of a Seagoing Cutter
        Suction Dredge (Adobe Acrobat 4.0 PDF-File 1.5 MB)". Proc. WODCON XII,
        Orlando, Florida, USA, April 1989. This paper was given the IADC Award for the
        best technical paper on the subject of dredging in 1989.
    26. Miedema, S.A., "The development of equipment for the determination of the wear on
        pick-points" (In Dutch). Delft University of Technology, 1990, 30 pages
        (90.3.GV.2749, BAGT 462).
    27. Miedema, S.A., "Excavating Bulk Materials" (In Dutch). Syllabus PATO course,
        1989 & 1991, PATO The Hague, The Netherlands.
    28. Miedema, S.A., "On the Cutting Forces in Saturated Sand of a Seagoing Cutter
        Suction Dredge (Adobe Acrobat 4.0 PDF-File 1.5 MB)". Terra et Aqua No. 41,
        December 1989, Elseviers Scientific Publishers.
    29. Miedema, S.A., "New Developments of Cutting Theories with respect to Dredging,
        the Cutting of Clay (Adobe Acrobat 4.0 PDF-File 640 kB)". Proc. WODCON XIII,
        Bombay, India, 1992.
    30. Davids, S.W. & Koning, J. de & Miedema, S.A. & Rosenbrand, W.F.,
        "Encapsulation: A New Method for the Disposal of Contaminated Sediment, a
        Feasibility Study (Adobe Acrobat 4.0 PDF-File 3MB)". Proc. WODCON XIII,
        Bombay, India, 1992.
    31. Miedema, S.A. & Journee, J.M.J. & Schuurmans, S., "On the Motions of a Seagoing
        Cutter Dredge, a Study in Continuity (Adobe Acrobat 4.0 PDF-File 396 kB)". Proc.
        WODCON XIII, Bombay, India, 1992.
    32. Becker, S. & Miedema, S.A. & Jong, P.S. de & Wittekoek, S., "On the Closing
        Process of Clamshell Dredges in Water Saturated Sand (Adobe Acrobat 4.0 PDF-File
        1 MB)". Proc. WODCON XIII, Bombay, India, 1992. This paper was given the IADC
        Award for the best technical paper on the subject of dredging in 1992.
    33. Becker, S. & Miedema, S.A. & Jong, P.S. de & Wittekoek, S., "The Closing Process
        of Clamshell Dredges in Water Saturated Sand (Adobe Acrobat 4.0 PDF-File 1 MB)".
        Terra et Aqua No. 49, September 1992, IADC, The Hague.
    34. Miedema, S.A., "Modeling and Simulation of Dredging Processes and Systems".
        Symposium "Zicht op Baggerprocessen", Delft University of Technology, Delft, The
        Netherlands, 29 October 1992.
    35. Miedema, S.A., "Dredmo User Interface, Operators Manual". Report: 92.3.GV.2995.
        Delft University of Technology, 1992, 77 pages.
    36. Miedema, S.A., "Inleiding Mechatronica, college WBM202" Delft University of
        Technology, 1992.



Copyright: Dr.ir. S.A. Miedema
     Miedema, S.A., "A Numerical Method of Calculating the Dynamic Behaviour of Hydraulic Transport".
     21st Annual Meeting & Technical Conference of the Western Dredging Association, June 2001, Houston, USA 2001.




    37. Miedema, S.A. & Becker, S., "The Use of Modeling and Simulation in the Dredging
        Industry, in Particular the Closing Process of Clamshell Dredges", CEDA Dredging
        Days 1993, Amsterdam, Holland, 1993.
    38. Miedema, S.A., "On the Snow-Plough Effect when Cutting Water Saturated Sand
        with Inclined Straight Blades (Adobe Acrobat 4.0 PDF-File 503 kB)". ASCE Proc.
        Dredging         94,      Orlando,      Florida,     USA,        November       1994.
        Additional Measurement Graphs. (Adobe Acrobat 4.0 PDF-File 209 kB).
    39. Riet, E. van, Matousek, V. & Miedema, S.A., "A Reconstruction of and Sensitivity
        Analysis on the Wilson Model for Hydraulic Particle Transport (Adobe Acrobat 4.0
        PDF-File 50 kB)". Proc. 8th Int. Conf. on Transport and Sedimentation of Solid
        Particles, 24-26 January 1995, Prague, Czech Republic.
    40. Vlasblom, W.J. & Miedema, S.A., "A Theory for Determining Sedimentation and
        Overflow Losses in Hoppers (Adobe Acrobat 4.0 PDF-File 304 kB)". Proc.
        WODCON IV, November 1995, Amsterdam, The Netherlands 1995.
    41. Miedema, S.A., "Production Estimation Based on Cutting Theories for Cutting Water
        Saturated Sand (Adobe Acrobat 4.0 PDF-File 423 kB)". Proc. WODCON IV,
        November            1995,        Amsterdam,        The        Netherlands       1995.
        Additional Specific Energy and Production Graphs. (Adobe Acrobat 4.0 PDF-File 145
        kB).
    42. Riet, E.J. van, Matousek, V. & Miedema, S.A., "A Theoretical Description and
        Numerical Sensitivity Analysis on Wilson's Model for Hydraulic Transport in
        Pipelines (Adobe Acrobat 4.0 PDF-File 50 kB)". Journal of Hydrology &
        Hydromechanics, Slovak Ac. of Science, Bratislava, June 1996.
    43. Miedema, S.A. & Vlasblom, W.J., "Theory for Hopper Sedimentation (Adobe
        Acrobat 4.0 PDF-File 304 kB)". 29th Annual Texas A&M Dredging Seminar. New
        Orleans, June 1996.
    44. Miedema, S.A., "Modeling and Simulation of the Dynamic Behavior of a
        Pump/Pipeline System (Adobe Acrobat 4.0 PDF-File 318 kB)". 17th Annual Meeting
        & Technical Conference of the Western Dredging Association. New Orleans, June
        1996.
    45. Miedema, S.A., "Education of Mechanical Engineering, an Integral Vision". Faculty
        O.C.P., Delft University of Technology, 1997 (in Dutch).
    46. Miedema, S.A., "Educational Policy and Implementation 1998-2003 (versions 1998,
        1999 and 2000) (Adobe Acrobat 4.0 PDF_File 195 kB)". Faculty O.C.P., Delft
        University of Technology, 1998, 1999 and 2000 (in Dutch).
    47. Keulen, H. van & Miedema, S.A. & Werff, K. van der, "Redesigning the curriculum
        of the first three years of the mechanical engineering curriculum". Proceedings of the
        International Seminar on Design in Engineering Education, SEFI-Document no.21,
        page 122, ISBN 2-87352-024-8, Editors: V. John & K. Lassithiotakis, Odense, 22-24
        October 1998.
    48. Miedema, S.A. & Klein Woud, H.K.W. & van Bemmel, N.J. & Nijveld, D., "Self
        Assesment Educational Programme Mechanical Engineering (Adobe Acrobat 4.0
        PDF-File 400 kB)". Faculty O.C.P., Delft University of Technology, 1999.
    49. Van Dijk, J.A. & Miedema, S.A. & Bout, G., "Curriculum Development Mechanical
        Engineering". MHO 5/CTU/DUT/Civil Engineering. Cantho University Vietnam,
        CICAT Delft, April 1999.
    50. Miedema, S.A., "Considerations in building and using dredge simulators (Adobe
        Acrobat 4.0 PDF-File 296 kB)". Texas A&M 31st Annual Dredging Seminar.
        Louisville Kentucky, May 16-18, 1999.




Copyright: Dr.ir. S.A. Miedema
     Miedema, S.A., "A Numerical Method of Calculating the Dynamic Behaviour of Hydraulic Transport".
     21st Annual Meeting & Technical Conference of the Western Dredging Association, June 2001, Houston, USA 2001.




    51. Miedema, S.A., "Considerations on limits of dredging processes (Adobe Acrobat 4.0
        PDF-File 523 kB)". 19th Annual Meeting & Technical Conference of the Western
        Dredging Association. Louisville Kentucky, May 16-18, 1999.
    52. Miedema, S.A. & Ruijtenbeek, M.G. v.d., "Quality management in reality",
        "Kwaliteitszorg in de praktijk". AKO conference on quality management in
        education. Delft University of Technology, November 3rd 1999.
    53. Miedema, S.A., "Curriculum Development Mechanical Engineering (Adobe Acrobat
        4.0 PDF-File 4 MB)". MHO 5-6/CTU/DUT. Cantho University Vietnam, CICAT
        Delft, Mission October 1999.
    54. Vlasblom, W.J., Miedema, S.A., Ni, F., "Course Development on Topic 5: Dredging
        Technology, Dredging Equipment and Dredging Processes". Delft University of
        Technology and CICAT, Delft July 2000.
    55. Miedema, S.A., Vlasblom, W.J., Bian, X., "Course Development on Topic 5:
        Dredging Technology, Power Drives, Instrumentation and Automation". Delft
        University of Technology and CICAT, Delft July 2000.
    56. Randall, R. & Jong, P. de & Miedema, S.A., "Experience with cutter suction dredge
        simulator training (Adobe Acrobat 4.0 PDF-File 1.1 MB)". Texas A&M 32nd Annual
        Dredging Seminar. Warwick, Rhode Island, June 25-28, 2000.
    57. Miedema, S.A., "The modelling of the swing winches of a cutter dredge in relation
        with simulators (Adobe Acrobat 4.0 PDF-File 814 kB)". Texas A&M 32nd Annual
        Dredging Seminar. Warwick, Rhode Island, June 25-28, 2000.
    58. Hofstra, C. & Hemmen, A. van & Miedema, S.A. & Hulsteyn, J. van, "Describing the
        position of backhoe dredges (Adobe Acrobat 4.0 PDF-File 257 kB)". Texas A&M
        32nd Annual Dredging Seminar. Warwick, Rhode Island, June 25-28, 2000.
    59. Miedema, S.A., "Automation of a Cutter Dredge, Applied to the Dynamic Behaviour
        of a Pump/Pipeline System (Adobe Acrobat 4.0 PDF-File 254 kB)". Proc. WODCON
        VI, April 2001, Kuala Lumpur, Malaysia 2001.
    60. Heggeler, O.W.J. ten, Vercruysse, P.M., Miedema, S.A., "On the Motions of Suction
        Pipe Constructions a Dynamic Analysis (Adobe Acrobat 4.0 PDF-File 110 kB)".
        Proc. WODCON VI, April 2001, Kuala Lumpur, Malaysia 2001.
    61. Miedema, S.A. & Zhao Yi, "An Analytical Method of Pore Pressure Calculations
        when Cutting Water Saturated Sand (Adobe Acrobat PDF-File 2.2 MB)". Texas
        A&M 33nd Annual Dredging Seminar, June 2001, Houston, USA 2001.
    62. Miedema, S.A., "A Numerical Method of Calculating the Dynamic Behaviour of
        Hydraulic Transport (Adobe Acrobat PDF-File 246 kB)". 21st Annual Meeting &
        Technical Conference of the Western Dredging Association, June 2001, Houston,
        USA 2001.
    63. Zhao Yi, & Miedema, S.A., "Finite Element Calculations To Determine The Pore
        Pressures When Cutting Water Saturated Sand At Large Cutting Angles (Adobe
        Acrobat PDF-File 4.8 MB)". CEDA Dredging Day 2001, November 2001,
        Amsterdam, The Netherlands.
    64. Miedema, S.A., "Mission Report Cantho University". MHO5/6, Phase Two, Mission
        to Vietnam by Dr.ir. S.A. Miedema DUT/OCP Project Supervisor, 27 September-8
        October 2001, Delft University/CICAT.
    65.            (Zhao         Yi),     &                                                (Miedema,          S.A.),
          "

          "
          (Finite Element Calculations To Determine The Pore Pressures When Cutting Water



Copyright: Dr.ir. S.A. Miedema
     Miedema, S.A., "A Numerical Method of Calculating the Dynamic Behaviour of Hydraulic Transport".
     21st Annual Meeting & Technical Conference of the Western Dredging Association, June 2001, Houston, USA 2001.




        Saturated Sand At Large Cutting Angles (Adobe Acrobat PDF-File 4.8 MB))". To be
        published in 2002.
    66. Miedema, S.A., & Riet, E.J. van, & Matousek, V., "Theoretical Description And
        Numerical Sensitivity Analysis On Wilson Model For Hydraulic Transport Of Solids
        In Pipelines (Adobe Acrobat PDF-File 147 kB)". WEDA Journal of Dredging
        Engineering, March 2002.
    67. Miedema, S.A., & Ma, Y., "The Cutting of Water Saturated Sand at Large Cutting
        Angles (Adobe Acrobat PDF-File 3.6 MB)". Proc. Dredging02, May 5-8, Orlando,
        Florida, USA.
    68. Miedema, S.A., & Lu, Z., "The Dynamic Behavior of a Diesel Engine (Adobe
        Acrobat PDF-File 363 kB)". Proc. WEDA XXII Technical Conference & 34th Texas
        A&M Dredging Seminar, June 12-15, Denver, Colorado, USA.
    69. Miedema, S.A., & He, Y., "The Existance of Kinematic Wedges at Large Cutting
        Angles (Adobe Acrobat PDF-File 4 MB)". Proc. WEDA XXII Technical Conference
        & 34th Texas A&M Dredging Seminar, June 12-15, Denver, Colorado, USA.
    70. Ma, Y., Vlasblom, W.J., Miedema, S.A., Matousek, V., "Measurement of Density and
        Velocity in Hydraulic Transport using Tomography". Dredging Days 2002, Dredging
        without boundaries, Casablanca, Morocco, V64-V73, 22-24 October 2002.
    71. Ma, Y., Miedema, S.A., Vlasblom, W.J., "Theoretical Simulation of the
        Measurements Process of Electrical Impedance Tomography". Asian Simulation
        Conference/5th International Conference on System Simulation and Scientific
        Computing, Shanghai, 3-6 November 2002, p. 261-265, ISBN 7-5062-5571-5/TP.75.
    72. Thanh, N.Q., & Miedema, S.A., "Automotive Electricity and Electronics". Delft
        University of Technology and CICAT, Delft December 2002.
    73. Miedema, S.A., Willemse, H.R., "Report on MHO5/6 Mission to Vietnam". Delft
        University of Technology and CICAT, Delft Januari 2003.
    74. Ma, Y., Miedema, S.A., Matousek, V., Vlasblom, W.J., "Tomography as a
        Measurement Method for Density and Velocity Distributions". 23rd WEDA
        Technical Conference & 35th TAMU Dredging Seminar, Chicago, USA, june 2003.
    75. Miedema, S.A., Lu, Z., Matousek, V., "Numerical Simulation of a Development of a
        Density Wave in a Long Slurry Pipeline". 23rd WEDA Technical Conference & 35th
        TAMU Dredging Seminar, Chicago, USA, june 2003.
    76. Miedema, S.A., Lu, Z., Matousek, V., "Numerical simulation of the development of
        density waves in a long pipeline and the dynamic system behavior". Terra et Aqua,
        No. 93, p. 11-23.
    77. Miedema, S.A., Frijters, D., "The Mechanism of Kinematic Wedges at Large Cutting
        Angles - Velocity and Friction Measurements". 23rd WEDA Technical Conference
        & 35th TAMU Dredging Seminar, Chicago, USA, june 2003.
    78. Tri, Nguyen Van, Miedema, S.A., Heijer, J. den, "Machine Manufacturing
        Technology". Lecture notes, Delft University of Technology, Cicat and Cantho
        University Vietnam, August 2003.
    79. Miedema, S.A., "MHO5/6 Phase Two Mission Report". Report on a mission to
        Cantho University Vietnam October 2003. Delft University of Technology and
        CICAT, November 2003.
    80. Zwanenburg, M., Holstein, J.D., Miedema, S.A., Vlasblom, W.J., "The Exploitation
        of Cockle Shells". CEDA Dredging Days 2003, Amsterdam, The Netherlands,
        November 2003.
    81. Zhi, L., Miedema, S.A., Vlasblom, W.J., Verheul, C.H., "Modeling and Simulation of
        the Dynamic Behaviour of TSHD's Suction Pipe System by using Adams". CHIDA
        Dredging Days, Shanghai, China, november 2003.



Copyright: Dr.ir. S.A. Miedema
     Miedema, S.A., "A Numerical Method of Calculating the Dynamic Behaviour of Hydraulic Transport".
     21st Annual Meeting & Technical Conference of the Western Dredging Association, June 2001, Houston, USA 2001.




    82. Miedema, S.A., "The Existence of Kinematic Wedges at Large Cutting Angles".
        CHIDA Dredging Days, Shanghai, China, november 2003.
    83. Miedema, S.A., Lu, Z., Matousek, V., "Numerical Simulation of the Development of
        Density Waves in a Long Pipeline and the Dynamic System Behaviour". Terra et
        Aqua 93, December 2003.
    84. Miedema, S.A. & Frijters, D.D.J., "The wedge mechanism for cutting of water
        saturated sand at large cutting angles". WODCON XVII, September 2004, Hamburg
        Germany.
    85. Verheul, O. & Vercruijsse, P.M. & Miedema, S.A., "The development of a concept
        for accurate and efficient dredging at great water depths". WODCON XVII,
        September 2004, Hamburg Germany.
    86. Miedema, S.A., "THE CUTTING MECHANISMS OF WATER SATURATED
        SAND AT SMALL AND LARGE CUTTING ANGLES". International Conference
        on Coastal Infrastructure Development - Challenges in the 21st Century. HongKong,
        november 2004.
    87. Ir. M. Zwanenburg , Dr. Ir. S.A. Miedema , Ir J.D. Holstein , Prof.ir. W.J.Vlasblom,
        "REDUCING THE DAMAGE TO THE SEA FLOOR WHEN DREDGING
        COCKLE SHELLS". WEDAXXIV & TAMU36, Orlando, Florida, USA, July 2004.
    88. Verheul, O. & Vercruijsse, P.M. & Miedema, S.A., "A new concept for accurate and
        efficient dredging in deep water". Ports & Dredging, IHC, 2005, E163.
    89. Miedema, S.A., "Scrapped?". Dredging & Port Construction, September 2005.
    90. Miedema, S.A. & Vlasblom, W.J., " Bureaustudie Overvloeiverliezen". In opdracht
        van Havenbedrijf Rotterdam, September 2005, Confidential.
    91. He, J., Miedema, S.A. & Vlasblom, W.J., "FEM Analyses Of Cutting Of Anisotropic
        Densely Compacted and Saturated Sand", WEDAXXV & TAMU37, New Orleans,
        USA, June 2005.
    92. Miedema, S.A., "The Cutting of Water Saturated Sand, the FINAL Solution".
        WEDAXXV & TAMU37, New Orleans, USA, June 2005.
    93. Miedema, S.A. & Massie, W., "Selfassesment MSc Offshore Engineering", Delft
        University of Technology, October 2005.
    94. Miedema, S.A., "THE CUTTING OF WATER SATURATED SAND, THE
        SOLUTION". CEDA African Section: Dredging Days 2006 - Protection of the
        coastline, dredging sustainable development, Nov. 1-3, Tangiers, Morocco.
    95. Miedema, S.A., "La solution de prélèvement par désagrégation du sable saturé en
        eau". CEDA African Section: Dredging Days 2006 - Protection of the coastline,
        dredging sustainable development, Nov. 1-3, Tangiers, Morocco.
    96. Miedema, S.A. & Vlasblom, W.J., "THE CLOSING PROCESS OF CLAMSHELL
        DREDGES IN WATER-SATURATED SAND". CEDA African Section: Dredging
        Days 2006 - Protection of the coastline, dredging sustainable development, Nov. 1-3,
        Tangiers, Morocco.
    97. Miedema, S.A. & Vlasblom, W.J., "Le processus de fermeture des dragues à benne
        preneuse en sable saturé". CEDA African Section: Dredging Days 2006 - Protection
        of the coastline, dredging sustainable development, Nov. 1-3, Tangiers, Morocco.
    98. Miedema, S.A. "THE CUTTING OF WATER SATURATED SAND, THE
        SOLUTION". The 2nd China Dredging Association International Conference &
        Exhibition, themed 'Dredging and Sustainable Development' and in Guangzhou,
        China, May 17-18 2006.
    99. Ma, Y, Ni, F. & Miedema, S.A., "Calculation of the Blade Cutting Force for small
        Cutting Angles based on MATLAB". The 2nd China Dredging Association




Copyright: Dr.ir. S.A. Miedema
     Miedema, S.A., "A Numerical Method of Calculating the Dynamic Behaviour of Hydraulic Transport".
     21st Annual Meeting & Technical Conference of the Western Dredging Association, June 2001, Houston, USA 2001.




         International Conference & Exhibition, themed 'Dredging and Sustainable
         Development' and in Guangzhou, China, May 17-18 2006.
    100.                                                        ,"
                                                       " (download). The 2nd China Dredging
       Association International Conference & Exhibition, themed 'Dredging and
       Sustainable Development' and in Guangzhou, China, May 17-18 2006.
    101.       Miedema, S.A. , Kerkvliet, J., Strijbis, D., Jonkman, B., Hatert, M. v/d, "THE
       DIGGING AND HOLDING CAPACITY OF ANCHORS". WEDA XXVI AND
       TAMU 38, San Diego, California, June 25-28, 2006.
    102.       Schols, V., Klaver, Th., Pettitt, M., Ubuan, Chr., Miedema, S.A., Hemmes, K.
       & Vlasblom, W.J., "A FEASIBILITY STUDY ON THE APPLICATION OF FUEL
       CELLS IN OIL AND GAS SURFACE PRODUCTION FACILITIES". Proceedings
       of FUELCELL2006, The 4th International Conference on FUEL CELL SCIENCE,
       ENGINEERING and TECHNOLOGY, June 19-21, 2006, Irvine, CA.
    103.       Miedema, S.A., "Polytechnisch Zakboek 51ste druk, Hoofdstuk G:
       Werktuigbouwkunde", pG1-G88, Reed Business Information, ISBN-10:
       90.6228.613.5, ISBN-13: 978.90.6228.613.3. Redactie: Fortuin, J.B., van Herwijnen,
       F., Leijendeckers, P.H.H., de Roeck, G. & Schwippert, G.A.
    104.       MA Ya-sheng, NI Fu-sheng, S.A. Miedema, "Mechanical Model of Water
       Saturated Sand Cutting at Blade Large Cutting Angles", Journal of Hohai University
       Changzhou,           ISSN          1009-1130,          CN        32-1591,         2006.
       绞刀片大角度切削水饱和沙的力学模型, 马亚生[1] 倪福生[1] S.A.Miedema[2],
       《河海大学常州分校学报》-2006年20卷3期 -59-61页
    105.       Miedema, S.A., Lager, G.H.G., Kerkvliet, J., “An Overview of Drag
       Embedded Anchor Holding Capacity for Dredging and Offshore Applications”.
       WODCON, Orlando, USA, 2007.
    106.       Miedema, S.A., Rhee, C. van, “A SENSITIVITY ANALYSIS ON THE
       EFFECTS OF DIMENSIONS AND GEOMETRY OF TRAILING SUCTION
       HOPPER DREDGES”. WODCON ORLANDO, USA, 2007.
    107.       Miedema, S.A., Bookreview: Useless arithmetic, why environmental scientists
       can't predict the future, by Orrin H. Pilkey & Linda Pilkey-Jarvis. Terra et Aqua 108,
       September 2007, IADC, The Hague, Netherlands.
    108.       Miedema, S.A., Bookreview: The rock manual: The use of rock in hydraulic
       engineering, by CIRIA, CUR, CETMEF. Terra et Aqua 110, March 2008, IADC, The
       Hague, Netherlands.
    109.       Miedema, S.A., "An Analytical Method To Determine Scour". WEDA
       XXVIII & Texas A&M 39. St. Louis, USA, June 8-11, 2008.
    110.       Miedema, S.A., "A Sensitivity Analysis Of The Production Of Clamshells".
       WEDA XXVIII & Texas A&M 39. St. Louis, USA, June 8-11, 2008.
    111.       Miedema, S.A., "An Analytical Approach To The Sedimentation Process In
       Trailing Suction Hopper Dredgers". Terra et Aqua 112, September 2008, IADC, The
       Hague, Netherlands.
    112.       Hofstra, C.F., & Rhee, C. van, & Miedema, S.A. & Talmon, A.M., "On The
       Particle Trajectories In Dredge Pump Impellers". 14th International Conference
       Transport & Sedimentation Of Solid Particles. June 23-27 2008, St. Petersburg,
       Russia.
    113.       Miedema, S.A., "A Sensitivity Analysis Of The Production Of Clamshells".
       WEDA Journal of Dredging Engineering, December 2008.




Copyright: Dr.ir. S.A. Miedema
     Miedema, S.A., "A Numerical Method of Calculating the Dynamic Behaviour of Hydraulic Transport".
     21st Annual Meeting & Technical Conference of the Western Dredging Association, June 2001, Houston, USA 2001.




    114.       Miedema, S.A., "New Developments Of Cutting Theories With Respect To
       Dredging, The Cutting Of Clay And Rock". WEDA XXIX & Texas A&M 40.
       Phoenix Arizona, USA, June 14-17 2009.
    115.       Miedema, S.A., "A Sensitivity Analysis Of The Scaling Of TSHD's". WEDA
       XXIX & Texas A&M 40. Phoenix Arizona, USA, June 14-17 2009.
    116.       Liu, Z., Ni, F., Miedema, S.A., “Optimized design method for TSHD’s swell
       compensator, basing on modelling and simulation”. International Conference on
       Industrial Mechatronics and Automation, pp. 48-52. Chengdu, China, May 15-16,
       2009.
    117.       Miedema, S.A., "The effect of the bed rise velocity on the sedimentation
       process in hopper dredges". Journal of Dredging Engineering, Vol. 10, No. 1 , 10-31,
       2009.
    118.       Miedema, S.A., “New developments of cutting theories with respect to
       offshore applications, the cutting of sand, clay and rock”. ISOPE 2010, Beijing China,
       June 2010.
    119.       Miedema, S.A., “The influence of the strain rate on cutting processes”. ISOPE
       2010, Beijing China, June 2010.
    120.       Ramsdell, R.C., Miedema, S.A., “Hydraulic transport of sand/shell mixtures”.
       WODCON XIX, Beijing China, September 2010.
    121.       Abdeli, M., Miedema, S.A., Schott, D., Alvarez Grima, M., “The application
       of discrete element modeling in dredging”. WODCON XIX, Beijing China,
       September 2010.
    122.       Hofstra, C.F., Miedema, S.A., Rhee, C. van, “Particle trajectories near
       impeller blades in centrifugal pumps. WODCON XIX, Beijing China, September
       2010.
    123.       Miedema, S.A., “Constructing the Shields curve, a new theoretical approach
       and its applications”. WODCON XIX, Beijing China, September 2010.
    124.       Miedema, S.A., “The effect of the bed rise velocity on the sedimentation
       process in hopper dredges”. WODCON XIX, Beijing China, September 2010.

 




Copyright: Dr.ir. S.A. Miedema

				
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