FLOW AROUND A CYLINDER - istiarto

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– iii – Flow around a Cylinder in a scoured Channel Bed Abstract The flow pattern around a cylinder protruding vertically on a scoured channel bed was experimentally and numerically investigated. Flow in an equilibrium scour hole (the scouring has ceased) under a clear water regime (no sediment supply into the scour hole) was considered. Detailed measurements were obtained with a non-intrusive instrument, the Acoustic Doppler Velocity Profiler (ADVP), which measures the profiles of the 3D instantaneous velocity vectors. The measurements were done in different vertical planes positioned around the cylinder. From the measured data, the spatial distributions of the mean (timeaveraged) velocities and its turbulence components could be deduced. The numerical simulations of the flow were performed by using a 3D model, which is developed based on the approximate solution of the time-averaged equations of motion and of continuity for incompressible flows by using a finite-volume method. The model uses the k-� turbulence closure model to compute the turbulence stresses and the Semi- Implicit Method for Pressure-Linked Equation (SIMPLE) method to link the velocity to the pressure. The discretisation of the equations were done following the hybrid and power-law schemes on a structured, collocated, hexahedral, body-fitted grid. While the essentials of the model are relatively standard, some detailed derivations and clarifications were elucidated about the boundary conditions and the pressure-velocity coupling. The measured velocity data show that a three-dimensional flow establishes itself, which is characterized by a rotating flow inside the scour hole upstream of the cylinder formed by a strong downward flow along the cylinder face and a reversed flow along the scour bed. This structure, which is known as horseshoe vortex, disappears behind the cylinder where a flow reversal towards the water surface is observed immediately behind the cylinder. These observations are supported by the numerical simulation. The measured turbulence intensities show a considerable increase inside the scour hole and in regions close to the cylinder. The turbulent kinetic energy increases on entering the scour hole, on approaching the cylinder, and on moving towards downstream regions. The profiles of the turbulent kinetic energy are characterized by bulges below the original bed level. Similar observations can be made for the Reynolds stresses. The numerical simulation under-predicted the turbulent kinetic energy, notably in the wake region immediately behind the cylinder. It appears that this problem is related to the
Page 1: FLOW AROUND A CYLINDER IN A SCOURED
Page 5 and 6: - v - Écoulement à Surface Libre
Page 7 and 8: - vii - Acknowledgements I wish to
Page 9 and 10: - ix - Table of Contents Abstract i
Page 11 and 12: - xi - 4.4 Pressure-velocity coupli
Page 13 and 14: Chapter 1 - 1.i - 1 Introduction 1.
Page 15 and 16: 1 Introduction 1.1 Flow around a cy
Page 17 and 18: - 1.3 - pitot tubes. Ahmed and Raja
Page 19 and 20: Chapter 2 - 2.i - 2 Flow Measuremen
Page 21 and 22: 2 Flow Measurements Abstract - 2.1
Page 23 and 24: 2.1 Measurement design - 2.3 - The
Page 25 and 26: - 2.5 - The water circuit is a clos
Page 27 and 28: - 2.7 - Consider a target ―i‖ m
Page 29 and 30: - 2.9 - Obtaining the velocity comp
Page 31 and 32: - 2.11 - Fig. 2.4 Cartesian and cyl
Page 33 and 34: - 2.13 - transducer were used, a fo
Page 35 and 36: - 2.15 - typically needed for this
Page 37 and 38: - 2.17 - 2.3.3 Comparison to other
Page 39 and 40: - 2.19 - Fig. 2.7 Scour hole geomet
Page 41 and 42: - 2.21 - Fig. 2.8 Distributions of
Page 43 and 44: u ��u �� u� � Du exp�
Page 45 and 46: - 2.25 - �o , and accordingly the
Page 47 and 48: - 2.27 - Measurements in zone A. Th
Page 49 and 50: - 2.29 - and 0.3 u �� u ��
Page 51 and 52: - 2.31 - Fig. 2.12b Cont’d.
Page 53 and 54:
- 2.33 - Fig. 2.12d Cont’d.
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2.5.4 Measurements in the plane �
Page 57 and 58:
- 2.37 - Fig. 2.13b Cont’d.
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- 2.39 - Fig. 2.13d Cont’d.
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- 2.41 - the solid boundary of the
Page 63 and 64:
- 2.43 - Fig. 2.14b Cont’d.
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- 2.45 - Fig. 2.14d Cont’d.
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- 2.47 - Turbulence intensities in
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- 2.49 - Fig. 2.15a Vertical distri
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- 2.51 - Fig. 2.15c Cont’d.
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- 2.53 - Reynolds stresses in the p
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- 2.55 - Fig. 2.16c Cont’d.
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2.6 Summary and conclusions - 2.57
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- 2.59 - Rolland, T. (1994). Develo
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Chapter 3 - 3.i - 3 Elaboration of
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- 3.1 - 3 Elaboration of the measur
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3.1 Introduction - 3.3 - Presented
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- 3.5 - Fig. 3.1 Measured velocity
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3.2.2 Flow pattern around the cylin
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- 3.9 - Fig. 3.2 Cont’d.
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Flow in the plane � = 45° and 90
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- 3.13 - Fig. 3.4 Contours of the m
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3.2.4 Vertical velocity (downward f
Page 99 and 100:
- 3.17 - flow may undergo a rotatin
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- 3.19 - Fig. 3.7 Cont’d.
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- 3.21 - A similar observation, in
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- 3.23 - Fig. 3.9 Measured turbulen
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The following is to be observed: -
Page 109 and 110:
- 3.27 - Fig. 3.10 Cont’d.
Page 111 and 112:
- 3.29 - 3.4 Bed shear-stresses alo
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x [cm] - 3.31 - Table 3.1 Estimated
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- 3.33 - Fig. 3.12 Estimated bed sh
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- 3.35 - (see Fig. 3.10 and Fig. 3.
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- 3.37 - Fig. 3.14 Axonometric pres
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- 3.39 - U, U∞ [m/s] sectional av
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Chapter 4 - 4.i - 4 Numerical Model
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- 4.1 - 4 Numerical Model Developme
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�u �t �v �t �w �t �
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- 4.5 - The volume integrals of the
Page 131 and 132:
- 4.7 - Fig. 4.1 Overall iterative
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- 4.9 - increase the computer stora
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- 4.11 - �� 1 ��
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- 4.13 - convective transport throu
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- 4.15 - n,��1 during a time st
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� for 0 � Pe e � q eL PE �
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4.3.8 Source terms - 4.19 - The sou
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2D � � � x �� b 2D �
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- 4.23 - b T � V P �t � n P
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- 4.25 - �� u ��1 � c i
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- 4.27 - Next, we need to define th
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4.5 Boundary conditions 4.5.1 Bound
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- 4.31 - The above relation holds a
Page 157 and 158:
- 4.33 - � extrapolate all variab
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G � � t 2 �V t - 4.35 - 2 �
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with � �� nt,b � ��
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- 4.39 - boundary node B are then a
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- 4.41 - Wall function for the �
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k and � equations - 4.43 - � se
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�� z-momentum: - 4.45 - ��1
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- 4.47 - � reconstruct the mesh,
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- 4.49 - Fig. 4.13 The structure of
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- 4.51 - ��
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4.7 Summary - 4.53 - Development of
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- 4.55 - B, �B [-] constant and w
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- 4.57 - �, � 1 , � p [-] und
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Chapter 5 - 5.i - 5 Numerical Simul
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5 Numerical Simulation Abstract - 5
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5.2 Experimental data - 5.3 - 5.2.1
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- 5.5 - computational nodes. The ot
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- 5.7 - (i) Yulistiyanto data (ii)
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- 5.9 - ( p � � 1 [mm]), but th
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- 5.11 - Fig. 5.4 Model test result
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- 5.13 - within a greater number of
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- 5.15 - Fig. 5.6 Computational his
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- 5.17 - 5.5 Simulation of flow aro
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- 5.19 - Fig. 5.9 Definition sketch
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- 5.21 - Fig. 5.10 Computed (lines)
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- 5.23 - Fig. 5.11 Computed and mea
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- 5.25 - 1.2U ∞ of the measuremen
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Water-surface profile - 5.27 - The
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- 5.29 - using a Joukowski transfor
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- 5.31 - 5.6.3 Results of the simul
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Velocity fields around the cylinder
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- 5.35 - Fig. 5.18 Computed and mea
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- 5.37 - than the measured one. The
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- 5.39 - Production and dissipation
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- 5.41 - Production of turbulent ki
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- 5.43 - If the above approach were
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- 5.45 - and surface profiles (see
Page 231 and 232:
- 5.47 - Fig. 5.24 Surface boundary
Page 233 and 234:
- 5.49 - S [m 2 ] surface area. So,
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Chapter 6 - 6.i - 6 Summary and Con
Page 237 and 238:
- 6.1 - 6 Summary and Conclusions 6
Page 239 and 240:
- 6.3 - The spatial distributions o
Page 241 and 242:
- 6.5 - � Laboratory measurements
Page 243 and 244:
- 6.7 - Fig. 6.1 Measured and compu
Page 245 and 246:
IDENTITE - 7.1 - Curriculum Vitæ N
Page 247 and 248:
FLOW AROUND A CYLINDER IN A SCOURED
Page 249 and 250:
- iii - Appendices Appendix A: Expe
Page 251 and 252:
A Experimental Data - A.1 - The exp
Page 253 and 254:
B Numerical Model B.1 Program struc
Page 255 and 256:
- B.3 -
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B.2 Input data file - B.5 - The inp
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- B.7 - #31 imon1, jmon1, kmon1 thr
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BLO for blocked cells, INL for inle
Page 263:
FLOW AROUND A CYLINDER IN A SCOURED
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