5% - eTheses Repository - University of Birmingham

More documents

Recommendations

Info

activities to the special problems involved in bed-particle dynamics. GOALS The project will entail experimental and computational investigations of the basic mechanisms involved in particle capture, transport and settling motions in the vicinity of defined bed forms. Three stages to the work are envisaged, as follows. Firstly, idealised small-scale studies will be executed in Birmingham, initially with particles on beds of fixed, sharp crested, geometries. Trajectory imaging and local flow measurements will be the main objective here, to identify precisely the role of vortex shedding and reattachment in the engagement and escape of individual particles. The aim will be to establish experimental conditions which can be realistically represented in detailed computational simulations of these unsteady events, using methods which have already been successfully used to diagnose previously unexplained phenomena in bubbly vortex flows. When the underlying structure has been properly characterised in this detailed fashion, we plan to develop both aspects of the project as follows. Secondly, on the experimental side, we shall extend the work using mobile beds to gauge the effects of evolving crest shapes and mass loading by suspended material on the transport capacity A2-2
of the vorticity shed into the near wake flows. Again, the emphasis in Birmingham will be complemented by the work at Wallingford where large-scale flumes are available for evaluating the fundamental modelling in situations which, though realistic, are still accessible to detailed interpretations and comparisons with the theoretical modelling. Thirdly, on the numerical side, we shall evaluate the implications of our computational modelling for the effective transport coefficients employed in engineering codes for shearturbulent bed flows: eg the eddy diffusivities of current closure schemes based on the k-e equations. Of special interest here will be to view the results in the light of recent field measurements of suspended sand transport over sandwaves made by MEHR (Soulsby, 1989) and, in particular to sensibly accommodate the inertially enhanced capture of particles by concentrated vorticity. In comparison with conventional theory, anomalous results have been reported regarding the distributions of fluid shear and particle concentrations over the bedform. Comparable anomalies have been found in the modelling of bubble transport by flows with concentrated vorticity and we are confident that realistic phenomenology can be incorporated in Reynolds averaged transport modelling of the particle fluxes. TRAINING The project will be conducted within securely established environments for flow transport dynamics research, both in the A2-3
Page 1 and 2:
FLUID-PARTICLE TRANSPORT DYNAMICS O
Page 3 and 4:
SYNOPSIS The local dynamics of sand
Page 5 and 6:
TABLE OF CONTENTS LIST OF FIGURES C
Page 7 and 8:
CHAPTER 3: JETTING EXPERIMENTS Summ
Page 9 and 10:
2 Numerical scheme 6-5 3 Results 6-
Page 11 and 12:
LIST OF FIGURES Chapter 1 Figure 1.
Page 13 and 14:
U=830mm/s. Figure 16. Thomas et al
Page 15 and 16:
in the boundary layer. a) The forma
Page 17 and 18:
Chapter 3 Figure 1. After Alien (19
Page 19 and 20:
at various values of U/V from 2.7 t
Page 21 and 22:
y Coanda-flapping of the free shear
Page 23 and 24:
of a sandwave crest in the estuary
Page 25 and 26:
Figure 7h-i. The temporal fluctuati
Page 27 and 28:
inclined downwards whereas the time
Page 29 and 30:
starting position (X,Y) at zero ini
Page 31 and 32:
d Sand grain diameter (m) Fi Number
Page 33 and 34:
G Vortex core growth rate (tn/s) ki
Page 35 and 36:
1 INTRODUCTION Sand forms the botto
Page 37 and 38:
where U is the depth-averaged veloc
Page 39 and 40:
The wavelengths of dunes primarily
Page 41 and 42:
detached and then confined within a
Page 43 and 44:
The vortex radius rn and apparent w
Page 45 and 46:
Recent work by Nezu & Nakagawa (199
Page 47 and 48:
found in the outer streaks. 4 MODEL
Page 49 and 50:
(1987), for example, modelled gas-s
Page 51 and 52:
Profiles of shear stress and turbul
Page 53 and 54:
6ft v "' ' Re In the limit of large
Page 55 and 56:
that the particle radius was much s
Page 57 and 58:
and travels downstream at speed }*U
Page 59 and 60:
capture by transient large eddies s
Page 61 and 62:
Chapter 1 Figure 3. Alien (1984). L
Page 63 and 64:
Chapter 1 10 8 e 4 I 08 •- 02 Yal
Page 65 and 66:
Chapter 1 bw speed fluid Figure 11.
Page 67 and 68:
Chapter 1 Figure 16. Thomas et al (
Page 69 and 70:
Chapter 1 StCMl STRESS SCALE « K /
Page 71 and 72:
Chapter 1 Haiht Vdodty Figure 22. S
Page 73 and 74:
Chapter 1 Time = 1.2 2.4 ' ' :•
Page 75 and 76:
1 INTRODUCTION AND DESIGN CONSIDERA
Page 77 and 78:
Initial costing for a flume of the
Page 79 and 80:
flanges and a maximum flow rate of
Page 81 and 82:
could be wound above or below the l
Page 83 and 84:
4 EXPERIMENTAL SETUP AND METHODS He
Page 85 and 86:
4.2 Flow visualisation and model pa
Page 87 and 88:
any divergence from the beam and to
Page 89 and 90:
even flow over 0.45m width and up t
Page 91 and 92:
Chapter 2 Opt 1 h(m) 0.01 Max D(m)
Page 93 and 94:
Chapter 2 Part of side section Putt
Page 95 and 96:
Chapter 2 Suction tank Bypass Disch
Page 97 and 98:
Chapter 2 QUncorrectedflow £ Corre
Page 99 and 100:
Chapter 2 60 r 501 40? 30r 20 r lOr
Page 101 and 102:
1_ INTRODUCTION The main features o
Page 103 and 104:
2 EXPERIMENTAL METHODS A detailed d
Page 105 and 106:
the relationship is then simply ^ -
Page 107 and 108:
number about 0.14. They were taken
Page 109 and 110:
along the stoss slope. Figures 8 an
Page 111 and 112:
3.3a) Jetting trajectories when U/V
Page 113 and 114:
errors increase substantially due t
Page 115 and 116:
likely distributions. 4 DISCUSSION
Page 117 and 118:
Our suggestion here is akin to that
Page 119 and 120:
not accommodate the differing migra
Page 121 and 122:
considered by proponents of numeric
Page 123 and 124:
Chapter 3 C,;: Figure 3a-j. The pla
Page 125 and 126:
Q CO 23 Figure 6. Distribution of p
Page 127 and 128:
Chapter 3 X(cm) 1 2 3 4 5 6 7 8 9 1
Page 129 and 130:
Chapter 3 U(m/s) V(m/s) U/V M1+M2 M
Page 131 and 132:
O I r+ 21 CO 2 5 8 11 14 17 20 23 >
Page 133 and 134:
8 11 14 17 20 23 25 + Position Figu
Page 135 and 136:
Chapter 3 U/V= B5.7 Q9.3 BlO.7^12.8
Page 137 and 138:
Chapter 3 Band 1 2 3 4 U(m/s) 0.2 0
Page 139 and 140:
1 INTRODUCTION In chapter 3 we cons
Page 141 and 142:
velocity for a maximum of 40% of th
Page 143 and 144:
layer vortices extending over the d
Page 145 and 146:
2.2 Methods for measuring Coanda-fl
Page 147 and 148:
Section 3.4 considers suspension fr
Page 149 and 150:
This same flow structure has also b
Page 151 and 152:
3.2b) Effect of varying inter-crest
Page 153 and 154:
those with fall speed 0.060m/s for
Page 155 and 156:
3.4 Particle capture from stoss slo
Page 157 and 158:
are discussed in the context of est
Page 159 and 160:
jetted grains settling to the lee s
Page 161 and 162:
Chapter 4 ENTRAINED FLOW Figure 1.
Page 163 and 164:
Figure 3a-j. The plates show partic
Page 165 and 166:
Chapter 4 Percentage occurrence •
Page 167 and 168:
Chapter 4 Interval (s) 60 80 100 12
Page 169 and 170:
Chapter 4 0.024m Conc=8% Figure 12.
Page 171 and 172:
Chapter 4 Figure 16. A cloud of par
Page 173 and 174:
1 INTRODUCTION We use a Rankine vor
Page 175 and 176:
effective particle fall speed in th
Page 177 and 178:
particle velocity Vx=0. The initial
Page 179 and 180:
the vortex axis. Vortex circulation
Page 181 and 182:
dimensional fall times T^ for diffe
Page 183 and 184:
horizontal component lift force (fi
Page 185 and 186:
corresponds to the trajectory trave
Page 187 and 188:
stepping the calculation in VT . Do
Page 189 and 190:
averaged exclusion of the coherent
Page 191 and 192:
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 and 244: figure 5, was critically dependant
Page 245 and 246: stoss slope suspension studies of c
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: APPENDIX 2: FAST9003.HR(RW)/NHT - P
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
Page 295 and 296: around the crest and the motion of
Page 297 and 298: micrometers, with mean of 80 microm
Page 299 and 300: i——COMPARISON WITH PREVIOUS WOR
Page 301 and 302: width speed (metres) ^(cm/s) 11 Fig
Page 303 and 304: U (33) = 1.16ms-' Depth = 2.65 m Fi
Page 305 and 306: APPENDIX 9 : DERIVATION OF FORCES O
Page 307 and 308: APPENDIX 10 : MODEL CODE FOR CALCUL
Page 309 and 310: APPENDIX 11: MODEL CODE FOR GROWING
Page 311: 105 if (scancode .eq. 57) stop GOTO
show all

5% - eTheses Repository - University of Birmingham

You also want an ePaper? Increase the reach of your titles

Delete template?

Save as template?