FLOW AROUND A CYLINDER - istiarto

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– 3.2 – entrant dans la fosse en s’approchant le cylindre ; sa valeur aux régions de sillage est très élevée. Les profils de l’énergie cinétique turbulente sont caractérisés par des pics qui se trouvent au dessous de la ligne du fond original. Les tensions de Reynolds augmentent de la même façon. L’estimation de la valeur de cisaillement au fond, à partir des donnée des vitesses et des tensions de Reynolds, met en évidence sa décroissance due à la fosse et au cylindre.
3.1 Introduction – 3.3 – Presented in the previous chapter are the velocity fields measured in five vertical planes radiating from the cylinder, � = 0°, 45°, 90°, 135°, and 180°. Brief discussions on the velocities, turbulence intensities, and Reynolds stresses were given following the presentation of the measurements in each plane. Detailed discussions are presented in this chapter where more emphasize is put rather on the (time-averaged) velocity. Most of the discussions are associated with the flow pattern in radial planes around the cylinder. A comparison with other relevant data in the available literature is also presented. 3.2 (Time-averaged) velocity fields Vertical distributions of measured (time-averaged) velocities in planes around the cylinder have been presented in Chapter 2. It has been shown that the flow outside the scour hole is not altered by the presence of the cylinder. The vertical distribution of the velocity outside the scour hole is very much similar to the one of the undisturbed flow. In the scour hole region, notably in the upper layer, z > 0, the effect of the cylinder is noticealbe in a region that is relatively close to the cylinder, r D p �1.3. In the lower layer, z < 0, and notably in the upstream planes, � ≤ 90°, the flow is characterized by a rotating flow and a downward flow, better known as the horseshoe vortex. This vortex is a result of interaction among the incoming flow, the scour hole, and the cylinder. It has also been presented that the velocity field is dominated by the u component in all measurement planes. Only very close to the cylinder the u component is exceeded by the vertical velocity. The w-velocity component manifests itself as a downward flow that reaches its strongest magnitude at the circumference of the cylinder. This downward flow gets weaker along the angular distance, � > 0°, and becomes upward flow in the rear of the cylinder, � = 180°. In the upstream planes, � ≤ 90°, it is through this downward flow that the incoming flow-momentum is transferred into the scour hole. The behavior of the downward flow in the upstream planes, � ≤ 90°, notably close to the cylinder, r = 10 [cm], will be further investigated (see Sect. 3.2.4).� The dominance of the u-velocity component over the v component over all planes, notably in the upstream planes, � ≤ 90°, is an interesting phenomenon. Measurements on a flat channel bed (see Graf and Yulistiyanto, 1998) show that in the plane � = 45° close to the cylinder, the u- and v-velocity components are comparable, indicating that the flow is directed tangentially with respect to the cylinder. This is not the case in the present measurements where the v component is persistently less pronounced. The dominant uvelocity component suggests that the incoming flow be directed straightforwardly to the downstream. This is most likely due to either the attraction of the scour hole to pull the flow or the momentum of the incoming flow. The incoming flow-momentum is strong enough to overcome any flow alteration by the cylinder. The spatial evolution of the vvelocity component will be discussed in Sect. 3.2.3.
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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
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 61 and 62: - 2.41 - the solid boundary of the
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: - 3.1 - 3 Elaboration of the measur
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 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 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
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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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- 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
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- 5.47 - Fig. 5.24 Surface boundary
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- 5.49 - S [m 2 ] surface area. So,
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Chapter 6 - 6.i - 6 Summary and Con
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- 6.1 - 6 Summary and Conclusions 6
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- 6.3 - The spatial distributions o
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- 6.5 - � Laboratory measurements
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- 6.7 - Fig. 6.1 Measured and compu
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IDENTITE - 7.1 - Curriculum Vitæ N
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- iii - Appendices Appendix A: Expe
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A Experimental Data - A.1 - The exp
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B Numerical Model B.1 Program struc
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- 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
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