FLOW AROUND A CYLINDER - istiarto

More documents

Recommendations

Info

– 5.32 – Fig. 5.16 Computed (lines) and measured (symbols) velocity distributions, u(z), v(z), w(z), at some selected stations around the cylinder Flow around a cylinder in a scoured channel bed.
Velocity fields around the cylinder – 5.33 – A more detailed observation of the flow pattern around the cylinder can be facilitated by plots of velocity vector and flow intensity contour, given in Fig. 5.17 and Fig. 5.18. The plots show the velocity vector, V� u r,w � �, and the flow intensity, V U � (V � u 2 � v 2 � w 2 and U � � 0.45 [m s]), in the planes � = 0°, 90°, and 180°. Note that for clarity purposes, not all but only some selected computed velocity vectors, being representative ones, are drawn. Shown also in the same figures are the ones obtained from the experimental data. Comparing the computed and the measured velocity fields shown in the two plots, it is evident that the two closely resemble. As in the flat-bed case, the model here also has proven its applicability to this highly 3D flow. Further remarks can be put forward from the plots in each of the three planes: � In the plane � = 0° (Fig. 5.17a,b and Fig. 5.18a,b), the unidirectional incoming flow is decelerating and deflecting towards the bed upon entering the scour hole. Close to the cylinder, the down-deflected flow becomes more pronounced and develops into a downward flow along the cylinder face. The stagnation pressure stimulates the downward flow, which is strengthening with increasing depth (decreasing z) and diminishing close to the bed, where the flow turns to the upstream direction along the bed. This reversed flow diminishes as it moves away from the cylinder and eventually joins the downstream facing upper flow. These downward and the reversed flows can be reasonably well captured by the model; the maximum computed downward flow, 0.5U ∞ , is slightly weaker than the measured one, 0.6U ∞ , but the computed reversed flow is comparable with the measured one, being both indicate an intensity of 0.2U ∞ (Fig. 5.18a,b). Note that the measurements show a strong reversed flow concentrated in a small region at the bottom corner of the cylinder, which the simulation cannot capture due to the limited spatial resolution of the grid. � In the plane � = 90° (Fig. 5.17c,d and Fig. 5.18c,d), both simulation and measurement show negligible radial and vertical velocity components as indicated by the vector plot (Fig. 5.17c,d). The contour plot (Fig. 5.18c,d) reveals, on the other hand, a comparable flow intensity as in the plane � = 0°. This shows that the flow is mainly directed towards downstream tangentially to the cylinder and that the lateral skewness of the approaching flow is negligible. � In the plane � = 180° (Fig. 5.17e,f and Fig. 5.18e,f), close to the cylinder the velocity is weak, 0.1 to 0.3U ∞ , and is directly upward towards the surface, where it turns upstream towards to the cylinder. Further downstream away from the cylinder, the flow is gradually increasing and returning to the approach flow condition. The close resemblance of the computed flow with the measured one is in fact a rather surprising since the flow behind the cylinder is a complex one.
Page 1 and 2:
FLOW AROUND A CYLINDER IN A SCOURED
Page 3 and 4:
- iii - Flow around a Cylinder in a
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.
Page 55 and 56:
2.5.4 Measurements in the plane �
Page 57 and 58:
- 2.37 - Fig. 2.13b Cont’d.
Page 59 and 60:
- 2.39 - Fig. 2.13d Cont’d.
Page 61 and 62:
- 2.41 - the solid boundary of the
Page 63 and 64:
- 2.43 - Fig. 2.14b Cont’d.
Page 65 and 66:
- 2.45 - Fig. 2.14d Cont’d.
Page 67 and 68:
- 2.47 - Turbulence intensities in
Page 69 and 70:
- 2.49 - Fig. 2.15a Vertical distri
Page 71 and 72:
- 2.51 - Fig. 2.15c Cont’d.
Page 73 and 74:
- 2.53 - Reynolds stresses in the p
Page 75 and 76:
- 2.55 - Fig. 2.16c Cont’d.
Page 77 and 78:
2.6 Summary and conclusions - 2.57
Page 79 and 80:
- 2.59 - Rolland, T. (1994). Develo
Page 81 and 82:
Chapter 3 - 3.i - 3 Elaboration of
Page 83 and 84:
- 3.1 - 3 Elaboration of the measur
Page 85 and 86:
3.1 Introduction - 3.3 - Presented
Page 87 and 88:
- 3.5 - Fig. 3.1 Measured velocity
Page 89 and 90:
3.2.2 Flow pattern around the cylin
Page 91 and 92:
- 3.9 - Fig. 3.2 Cont’d.
Page 93 and 94:
Flow in the plane � = 45° and 90
Page 95 and 96:
- 3.13 - Fig. 3.4 Contours of the m
Page 97 and 98:
3.2.4 Vertical velocity (downward f
Page 99 and 100:
- 3.17 - flow may undergo a rotatin
Page 101 and 102:
- 3.19 - Fig. 3.7 Cont’d.
Page 103 and 104:
- 3.21 - A similar observation, in
Page 105 and 106:
- 3.23 - Fig. 3.9 Measured turbulen
Page 107 and 108:
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
Page 113 and 114:
x [cm] - 3.31 - Table 3.1 Estimated
Page 115 and 116:
- 3.33 - Fig. 3.12 Estimated bed sh
Page 117 and 118:
- 3.35 - (see Fig. 3.10 and Fig. 3.
Page 119 and 120:
- 3.37 - Fig. 3.14 Axonometric pres
Page 121 and 122:
- 3.39 - U, U∞ [m/s] sectional av
Page 123 and 124:
Chapter 4 - 4.i - 4 Numerical Model
Page 125 and 126:
- 4.1 - 4 Numerical Model Developme
Page 127 and 128:
�u �t �v �t �w �t �
Page 129 and 130:
- 4.5 - The volume integrals of the
Page 131 and 132:
- 4.7 - Fig. 4.1 Overall iterative
Page 133 and 134:
- 4.9 - increase the computer stora
Page 135 and 136:
- 4.11 - �� 1 ��
Page 137 and 138:
- 4.13 - convective transport throu
Page 139 and 140:
- 4.15 - n,��1 during a time st
Page 141 and 142:
� for 0 � Pe e � q eL PE �
Page 143 and 144:
4.3.8 Source terms - 4.19 - The sou
Page 145 and 146:
2D � � � x �� b 2D �
Page 147 and 148:
- 4.23 - b T � V P �t � n P
Page 149 and 150:
- 4.25 - �� u ��1 � c i
Page 151 and 152:
- 4.27 - Next, we need to define th
Page 153 and 154:
4.5 Boundary conditions 4.5.1 Bound
Page 155 and 156:
- 4.31 - The above relation holds a
Page 157 and 158:
- 4.33 - � extrapolate all variab
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
Page 183 and 184: Chapter 5 - 5.i - 5 Numerical Simul
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
Page 195 and 196: - 5.11 - Fig. 5.4 Model test result
Page 197 and 198: - 5.13 - within a greater number of
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)
Page 207 and 208: - 5.23 - Fig. 5.11 Computed and mea
Page 209 and 210: - 5.25 - 1.2U ∞ of the measuremen
Page 211 and 212: Water-surface profile - 5.27 - The
Page 213 and 214: - 5.29 - using a Joukowski transfor
Page 215: - 5.31 - 5.6.3 Results of the simul
Page 219 and 220: - 5.35 - Fig. 5.18 Computed and mea
Page 221 and 222: - 5.37 - than the measured one. The
Page 223 and 224: - 5.39 - Production and dissipation
Page 225 and 226: - 5.41 - Production of turbulent ki
Page 227 and 228: - 5.43 - If the above approach were
Page 229 and 230: - 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,
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
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 -
Page 257 and 258: B.2 Input data file - B.5 - The inp
Page 259 and 260: - B.7 - #31 imon1, jmon1, kmon1 thr
Page 261 and 262: BLO for blocked cells, INL for inle
Page 263: FLOW AROUND A CYLINDER IN A SCOURED
show all

FLOW AROUND A CYLINDER - istiarto

Create successful ePaper yourself

Delete template?

Save as template?