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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