FLOW AROUND A CYLINDER - istiarto

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– 5.24 – Fig. 5.12 Computed and measured velocity contours, in the planes � = 0°, 90°, 180°. The data are normalized by the velocity in the approach flow, V U � , where V � u 2 � v 2 � w 2 and U∞ = 0.45 [m/s]. Flow around a cylinder on a flat channel bed.�
– 5.25 – 1.2U ∞ of the measurement. Note that the vector plot of the measured velocity at this corner indicates some scattered data as has also been mentioned in the preceding section. � In the plane � = 180°, both the simulation and the measurement exhibit a counter rotating flow towards the surface (Fig. 5.11e,f). Except close to the bed, the intensities of the rotating flow obtained by the simulation and measurement are quite comparable (Fig. 5.12e,f). Immediately behind the cylinder, the agreement is quite satisfactory. Leaving the cylinder, the rotating flow diminishes and the flow returns back to the unidirectional flow condition. Vorticity fields in the bottom corner around the cylinder Another way of observing the flow around a cylinder is to use the vorticity fields whose component in a vertical plane � is defined by (Graf and Yulistiyanto, 1998):� �� w �r � �ur �z (5.3) in which the velocity gradients are obtained by using finite volume techniques (see Chapter 4) for the computed data and by using central finite difference for the measured data. It must be emphasized, however, that the vorticity is highly sensitive to the quality and quantity of the measured data points. The measured vorticity fields thus have to be interpreted with caution. Shown in Fig. 5.13 are the contour plots of the vorticity fields in the planes � = 0°, 90°, and 180° obtained from the simulation and the measurement. Only the bottom corner region, where the vorticity is of importance, is presented. The following is to be remarked: � Upstream of the cylinder, in the plane � = 0°, a qualitative agreement is observed between the computed and measured vorticity fields, notably the negative vorticities formed by the downward flow close to the cylinder. A qualitative, bot not quantitative, agreement is also observed by the positive vorticity fields in the bottom corner of the cylinder formed by the downward flow and the reversed flow. The strong concentrated vorticity shown by the measurements, however, cannot be captured.� � On the side of the cylinder, in the plane � = 90°, the agreement is less evident, apart from the negative vorticity region close to the bed. This negative vorticity is formed by the radiating flow away from the cylinder as has been mentioned in the preceding section. There is also a negative vorticity region along the cylinder, produced by the downward flow. The strong positive vorticity at z = 2 [cm], which is shown by the measured fields, cannot be reproduced by the simulation.�
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FLOW AROUND A CYLINDER IN A SCOURED
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- iii - Flow around a Cylinder in a
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- v - Écoulement à Surface Libre
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- vii - Acknowledgements I wish to
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- ix - Table of Contents Abstract i
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- xi - 4.4 Pressure-velocity coupli
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Chapter 1 - 1.i - 1 Introduction 1.
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1 Introduction 1.1 Flow around a cy
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- 1.3 - pitot tubes. Ahmed and Raja
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Chapter 2 - 2.i - 2 Flow Measuremen
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2 Flow Measurements Abstract - 2.1
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2.1 Measurement design - 2.3 - The
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- 2.5 - The water circuit is a clos
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- 2.7 - Consider a target ―i‖ m
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- 2.9 - Obtaining the velocity comp
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- 2.11 - Fig. 2.4 Cartesian and cyl
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- 2.13 - transducer were used, a fo
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- 2.15 - typically needed for this
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- 2.17 - 2.3.3 Comparison to other
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- 2.19 - Fig. 2.7 Scour hole geomet
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- 2.21 - Fig. 2.8 Distributions of
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u ��u �� u� � Du exp�
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- 2.25 - �o , and accordingly the
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- 2.27 - Measurements in zone A. Th
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- 2.29 - and 0.3 u �� u ��
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- 2.31 - Fig. 2.12b Cont’d.
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- 2.33 - Fig. 2.12d Cont’d.
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2.5.4 Measurements in the plane �
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- 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
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- 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
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- 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: -
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- 3.27 - Fig. 3.10 Cont’d.
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- 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
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- 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
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Page 159 and 160: G � � t 2 �V t - 4.35 - 2 �
Page 161 and 162: with � �� nt,b � ��
Page 163 and 164: - 4.39 - boundary node B are then a
Page 165 and 166: - 4.41 - Wall function for the �
Page 167 and 168: k and � equations - 4.43 - � se
Page 169 and 170: �� z-momentum: - 4.45 - ��1
Page 171 and 172: - 4.47 - � reconstruct the mesh,
Page 173 and 174: - 4.49 - Fig. 4.13 The structure of
Page 175 and 176: - 4.51 - ��
Page 177 and 178: 4.7 Summary - 4.53 - Development of
Page 179 and 180: - 4.55 - B, �B [-] constant and w
Page 181 and 182: - 4.57 - �, � 1 , � p [-] und
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Page 185 and 186: 5 Numerical Simulation Abstract - 5
Page 187 and 188: 5.2 Experimental data - 5.3 - 5.2.1
Page 189 and 190: - 5.5 - computational nodes. The ot
Page 191 and 192: - 5.7 - (i) Yulistiyanto data (ii)
Page 193 and 194: - 5.9 - ( p � � 1 [mm]), but th
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Page 199 and 200: - 5.15 - Fig. 5.6 Computational his
Page 201 and 202: - 5.17 - 5.5 Simulation of flow aro
Page 203 and 204: - 5.19 - Fig. 5.9 Definition sketch
Page 205 and 206: - 5.21 - Fig. 5.10 Computed (lines)
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Page 211 and 212: Water-surface profile - 5.27 - The
Page 213 and 214: - 5.29 - using a Joukowski transfor
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Page 217 and 218: Velocity fields around the cylinder
Page 219 and 220: - 5.35 - Fig. 5.18 Computed and mea
Page 221 and 222: - 5.37 - than the measured one. The
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Page 231 and 232: - 5.47 - Fig. 5.24 Surface boundary
Page 233 and 234: - 5.49 - S [m 2 ] surface area. So,
Page 235 and 236: 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
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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
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Page 257 and 258: 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
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FLOW AROUND A CYLINDER IN A SCOURED
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