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Coanda flapping phenomenon involved manual analysis which was exceedingly time consuming. Introduction of PIV and frame-byframe automated analysis would solve this problem. Specifically here, such a system could interrogate frames for the recovery of the effective separation volume by finding the first occurrence of directionally-pulse-tagged streaks formed by flow tracers. The remaining streaks caused by flow tracers looping and travelling in the opposite direction must then be part of the recirculation bubble, giving the time dependent bubble size. This study would surely demonstrate that fluctuations here are directly linked to the Coanda-flapping frequency. Concurrent video records of the crest flow could also be analysed, allowing, for example, subtraction of the mean flow to produce pictures of the shear layer vortices arriving at the crest and again producing a frequency for the possible driving events. Chapters 3 and 4 described particle trajectory information which revealed interesting information but statistically converged data is difficult to achieve by manual analysis alone. We now have automatic particle tracking equipment available which should eradicate this problem. It will also allow two-point correlation methods to be used which will probably prove the modal trajectory theory. It will also be useful when considering lee slope suspension and the concentration profiles thereof. The problem of starting flow washout as encountered during the 7-8
stoss slope suspension studies of chapter 4 are difficult to overcome. One plausible approach would involve attaching a layer of particles to the bedforms providing a rough surface for retention of a second layer of free particles. Should this prove insufficient to solve the problem then magnetics may provide the answer. Each particle could conceivably be coated with, say, iron powder and held to the bedform during flow development with an electromagnet either beneath the flume or built into the bedform. 3.2 Numerical modelling techniques The fixed core modelling of chapter 5 should be extended to encompass more starting conditions and different vorticity distributions such as the Gaussian core. Essentially, the criterion C(X,Y,VX ,VY ) should be found for all relevant values of the initial position (X,Y) of the particle at initial velocities (VX ,VY ) . For the sandwave problem (X,Y) should be considered from (-20,-20) to (20,20) at (VX ,VY ) from (0,-VT ) to (U,0) where U is the maximum mean stream speed, about say 2m/s for dunes. This comprehensive set would be too large to be of use directly, but would allow rules to be defined concerning particle capture and ejection which should be of more general use to modellers. The growing vortex model of the shear layer should be extended to include different growth laws ie adapted to account for shear layers that do not have constant velocity difference. This is needed because the shear layer over sandwaves cannot sensibly 7-9
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FLUID-PARTICLE TRANSPORT DYNAMICS O
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SYNOPSIS The local dynamics of sand
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TABLE OF CONTENTS LIST OF FIGURES C
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CHAPTER 3: JETTING EXPERIMENTS Summ
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2 Numerical scheme 6-5 3 Results 6-
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LIST OF FIGURES Chapter 1 Figure 1.
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U=830mm/s. Figure 16. Thomas et al
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in the boundary layer. a) The forma
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Chapter 3 Figure 1. After Alien (19
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at various values of U/V from 2.7 t
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y Coanda-flapping of the free shear
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of a sandwave crest in the estuary
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Figure 7h-i. The temporal fluctuati
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inclined downwards whereas the time
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starting position (X,Y) at zero ini
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d Sand grain diameter (m) Fi Number
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G Vortex core growth rate (tn/s) ki
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1 INTRODUCTION Sand forms the botto
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where U is the depth-averaged veloc
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The wavelengths of dunes primarily
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detached and then confined within a
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The vortex radius rn and apparent w
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Recent work by Nezu & Nakagawa (199
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found in the outer streaks. 4 MODEL
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(1987), for example, modelled gas-s
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Profiles of shear stress and turbul
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6ft v "' ' Re In the limit of large
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that the particle radius was much s
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and travels downstream at speed }*U
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capture by transient large eddies s
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Chapter 1 Figure 3. Alien (1984). L
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Chapter 1 10 8 e 4 I 08 •- 02 Yal
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Chapter 1 bw speed fluid Figure 11.
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Chapter 1 Figure 16. Thomas et al (
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Chapter 1 StCMl STRESS SCALE « K /
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Chapter 1 Haiht Vdodty Figure 22. S
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Chapter 1 Time = 1.2 2.4 ' ' :•
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1 INTRODUCTION AND DESIGN CONSIDERA
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Initial costing for a flume of the
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flanges and a maximum flow rate of
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could be wound above or below the l
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4 EXPERIMENTAL SETUP AND METHODS He
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4.2 Flow visualisation and model pa
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any divergence from the beam and to
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even flow over 0.45m width and up t
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Chapter 2 Opt 1 h(m) 0.01 Max D(m)
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Chapter 2 Part of side section Putt
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Chapter 2 Suction tank Bypass Disch
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Chapter 2 QUncorrectedflow £ Corre
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Chapter 2 60 r 501 40? 30r 20 r lOr
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1_ INTRODUCTION The main features o
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2 EXPERIMENTAL METHODS A detailed d
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the relationship is then simply ^ -
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number about 0.14. They were taken
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along the stoss slope. Figures 8 an
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3.3a) Jetting trajectories when U/V
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errors increase substantially due t
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likely distributions. 4 DISCUSSION
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Our suggestion here is akin to that
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not accommodate the differing migra
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considered by proponents of numeric
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Chapter 3 C,;: Figure 3a-j. The pla
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Q CO 23 Figure 6. Distribution of p
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Chapter 3 X(cm) 1 2 3 4 5 6 7 8 9 1
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Chapter 3 U(m/s) V(m/s) U/V M1+M2 M
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O I r+ 21 CO 2 5 8 11 14 17 20 23 >
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8 11 14 17 20 23 25 + Position Figu
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Chapter 3 U/V= B5.7 Q9.3 BlO.7^12.8
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Chapter 3 Band 1 2 3 4 U(m/s) 0.2 0
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1 INTRODUCTION In chapter 3 we cons
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velocity for a maximum of 40% of th
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layer vortices extending over the d
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2.2 Methods for measuring Coanda-fl
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Section 3.4 considers suspension fr
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This same flow structure has also b
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3.2b) Effect of varying inter-crest
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those with fall speed 0.060m/s for
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3.4 Particle capture from stoss slo
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are discussed in the context of est
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jetted grains settling to the lee s
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Chapter 4 ENTRAINED FLOW Figure 1.
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Figure 3a-j. The plates show partic
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Chapter 4 Percentage occurrence •
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Chapter 4 Interval (s) 60 80 100 12
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Chapter 4 0.024m Conc=8% Figure 12.
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Chapter 4 Figure 16. A cloud of par
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1 INTRODUCTION We use a Rankine vor
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effective particle fall speed in th
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particle velocity Vx=0. The initial
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the vortex axis. Vortex circulation
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dimensional fall times T^ for diffe
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horizontal component lift force (fi
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corresponds to the trajectory trave
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stepping the calculation in VT . Do
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averaged exclusion of the coherent
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C from figure 11 (ie 2.2) then we h
Page 193 and 194: PflRTICLE DENSITY=1000.000 Kg/n3 LI
Page 195 and 196: Chapter 5 ft) J k I Figure 4. Varyi
Page 197 and 198: Chapter 5 Relative Fall Time va Sta
Page 199 and 200: Chapter 5 Figure 7a. Trajectories o
Page 201 and 202: Chapter 5 Velocity X —Inertia X L
Page 203 and 204: Chapter 5 Velocity X —Velocity Y
Page 205 and 206: Chapter 5 Velocity Y Inertia Y Lift
Page 207 and 208: Chapter 5 DENSITY PARTICLE=2850.000
Page 209 and 210: Chapter 5 Rad = 0.006 Rad=0.003 Rad
Page 211 and 212: Chapter 5 H3 Y=0 Oy=i m Y=2 D-y=3
Page 213 and 214: CHAPTER 6: NUMERICAL SIMULATION OF
Page 215 and 216: next. If we now adopt the classical
Page 217 and 218: st = (4) Where p p was the particle
Page 219 and 220: 3 RESULTS 3.1 Specified 6 and V Fig
Page 221 and 222: the blue squares to double loops an
Page 223 and 224: A0fl0 = 1.25V-0.33G-0.005 (7) and f
Page 225 and 226: Conversely, the upper line of the p
Page 227 and 228: equations. Such a discrete vortex m
Page 229 and 230: Figure 1. Schematic of the shear la
Page 231 and 232: Chapter 6 J G H K M Figure 3. Seven
Page 233 and 234: Chapter 6 1 T V=0.161 0.1 -- V41185
Page 235 and 236: Chapter 6 - DataV=0.0335, G=0.01
Page 237 and 238: CHAPTER 7: RECAPITULATION AND RECOM
Page 239 and 240: were shown to compare well with pre
Page 241 and 242: We have shown Coanda-flapping makes
Page 243: figure 5, was critically dependant
Page 247 and 248: Figure la-g. The seven trajectory m
Page 249 and 250: Chapter 7
Page 251 and 252: Chapter 7 0.0351 0.03 " 03 0.025 0.
Page 253 and 254: Flow 16 (1) pp 19-34. Bernal LP (19
Page 255 and 256: Mechanics of Sediment Transport. Is
Page 257 and 258: turbulence near a smooth wall in a
Page 259 and 260: moderate Reynolds number shear laye
Page 261 and 262: Spalding (1961). A single formula f
Page 263 and 264: USA. 1-12
Page 265 and 266: APPENDIX 1: BOUNDARY LAYER STUDIES
Page 267 and 268: (1967) used hydrogen bubble visuali
Page 269 and 270: The burst-sweep dynamics study of U
Page 271 and 272: Horseshoe vortex Vortex filament Ho
Page 273 and 274: APPENDIX 2: FAST9003.HR(RW)/NHT - P
Page 275 and 276: of the vorticity shed into the near
Page 277 and 278: transport dynamics of multiphase fl
Page 279 and 280: APPENDIX 3: FUNDAMENTAL NAVIER-STOK
Page 281 and 282: APPENDIX 4: CLOSURE METHODS 1 ZERO
Page 283 and 284: where cr k and CD are empirical con
Page 285 and 286: K = CDe^ 2 p 2 \U2 -U1 \=e 1e 2 c (
Page 287 and 288: APPENDIX 6: K-e MODEL OF JOHNS ET A
Page 289 and 290: They then defined a hydrodynamic co
Page 291 and 292: with respect to the rest of the vor
Page 293 and 294: The vorticity equation can be split
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around the crest and the motion of
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micrometers, with mean of 80 microm
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i——COMPARISON WITH PREVIOUS WOR
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width speed (metres) ^(cm/s) 11 Fig
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U (33) = 1.16ms-' Depth = 2.65 m Fi
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APPENDIX 9 : DERIVATION OF FORCES O
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APPENDIX 10 : MODEL CODE FOR CALCUL
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APPENDIX 11: MODEL CODE FOR GROWING
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105 if (scancode .eq. 57) stop GOTO
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