dam hydraulic

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Dam Hydraulics

D L Vischer

W H HagerETH-Zentrum Zurich Switzerland

JO HN WILEY SONSChichester New York Weinheim Brisbane Singapore Toronto



Contents

Preface ix

1 Introduction 11.1 W hat is dam hydraulics? 11.2 Descrip tion of dam hydraulics 21.3 Design discharge of bot tom outlet 8

1.3.1 Purp ose of bot tom outlet 81.3.2 Dra wd ow n of reservoir 101.3.3 Flu shing of sedim ents 111.3.4 Flo od and residual discharge 121.3.5 Possib ilities of failure 12

1.4 Design disch arge of spillway 131.4.1 Co ncept of crest height 131.4.2 Con cept of water volumes 16

1.4.3 Co nce pt of discharges 171.4.4 Design assump tion 191.5 Design discharge of intake structure 21

1.5.1 Pu rpo se 211.5.2 Storag e characteristics 211.5.3 Reservo ir storage 221.5.4 Design principle and stand ard values 24

1.6 Design discharge of diversion tunne l or channe l 241.6.1 Purp ose of diversion 241.6.2 Co nce pts of design 251.6.3 Choice of design flood 26

References 27

2 Overflow Stru ctu res 312.1 Introductio n 31

2.1.1 Overflow gates 312.1.2 Overflow types 332.1.3 Significance of overflow struc ture 39

2.2 Fr on tal overflow 392.2.1 Crest shapes 392.2.2 Sta nda rd crest 402.2.3 Free surface profile 442.2.4 Disch arge characteristics 44

2.2.5 Bo ttom pressure characteristics 452.2.6 Velocity distribu tion 462.2.7 Cav itation design 50



vi Contents

2.2.8 Overflow piers 502.2.9 Overflow gates 54

2.3 Side channel 572.3.1 Typology 57

2.3.2 Hy draulic design 602.3.3 Spatial flow features 62

2.4 M orning Glory overfall 642.4.1 Con cept 642.4.2 Crest shape 662.4.3 Discharge and pressure characteristics 682.4.4 Loca tion of overflow struct ure 692.4.5 Vertical shaft 692.4.6 Shaft aera tion 72

2.5 Siphon 762.5.1 Description of siphons 76

2.5.2 Blackwater siphon 782.5.3 W hitewater siphon 80References 82

8787

89

89

9

9

97

98

98

2

3

3

3

7

2 5

7

7

9

23

3

47

5

5 Dissipation Stru cture s 1555.1 Introd uctio n 1555.2 Hy draulic jum p and stilling basin 158

5.2.1 Classical hydraulic jum p 1585.2.2 Stilling basins 1625.2.3 Basin characteristics 172

Diversion3.13.2

3.3

3.4

i StructuresIntroductionDiversion tunnel3.2.13.2.23.2.33.2.4River3.3.13.3.23.3.3

IntroductionInlet to diversion tunnelTunnel flowOutlet structure

diversionEffect of constrictionTransitional flowSubcritical flow

Culvert3.4.13.4.2

References

IntroductionHydraulic design

Outlet Structures4.1

4.2

4.3

Free fall4.1.1

4.1.24.1.3Chute4.2.14.2.24.2.34.2.4

Introduction

Jet trajectoryJet impact

Hydraulic designSurface air entrainmentChute aeratorShockwaves

Cascade spillwayReferences



Contents vii

5.3 D ro p structures and plunge pools 1755.3.1 Basic flow feature s 1755.3.2 Im pac t structu res 1775.3.3 Scou r characteristics 177

5.4 Trajecto ry basin s 1785.4.1 De scrip tion of structu re 178

179181184185

89189192198199199202203206206207208210211212

In take S t ruc tures 2157.1 Introd uction 2157.2 Bottom intak e 217

7.2.1 Design principles 2177.2.2 Orifice flow 2187.2.3 Inlet geom etry 220

7.3 Surface int ak e 2217.3.1 Vo rtex flow 2217.3.2 Vertical intake vortex 2227.3.3 Limit subm ergence 2257.3.4 Design recom men dations 228

7.4 Practic al aspec ts 2307.4.1 Preve ntion of floating m atte r 2307.4.2 Emergency gate closure 231

References 232

Reservoir Sed imentat ion 2358.1 Introd uctio n 2358.2 Me thods of sediment removal 237

8.2.1 Direct me thods 2378.2.2 Gr ave l basins 2378.2.3 Fr on t basin 2388.2.4 Res ervoir dredging 238

8.2.5 Clea ring of dam outlet 2398.2.6 Reservo ir emptying 241

8.3 Density curren ts 2428.3.1 Definition 242

5.4.25.4.35.4.4

References

Bottom <

TakeoffJet disintegrationScour

Outlets6.1 Design principles6.2 Gate6.3 Gate

types and design requirementsvibration

6.4 Hydraulics of high-head gates6.4.16.4.2

Discharge equationGate slots

6.5 Air entrainm ent6.6 Cavitation

6.6.16.6.26.6.36.6.46.6.5

References

DescriptionBubble collapse dynamicsCavitation characteristicsCavitation damageControl of cavitation



viii

8.3.2 Plunge point8.3.3 Equilibrium flow8.3.4 Intrusion

8.4 Sediment control8.4.1 Turb ulent suspension8.4.2 Turbidity currents8.4.3 Flushing of sediments

8.5 Secon dary hydraulic effects of reservoir sedim entatio n8.5.1 Up stream river8.5.2 Dow nstream river8.5.3 Disposal of sediments

References

9 Impu lse W aves from Sh ore Instabilities9.1 Introduction9.2 Impulse waves

9.2.1 Wave theories9.2.2 Impu lse waves

9.3 Generation of impulse waves9.3.1 Wave generation by mo ving wedge9.3.2 W ave generation by falling mass9.3.3 Spatial impulse waves

9.4 Imp act of impulse waves9.4.1 Gove rning param eters9.4.2 Ru nu p mechan ism9.4.3 Ru nu p height

9.5 Overtop ping of impulse waves

9.5.1 Description of pheno men on9.5.2 Description of over topp ing9.5.3 Characteristics of overto pping

9.6 RemarksReferences

10 Dam break Waves10.1 Introduction10.2 Dam breaching

10.2.1 Breaching characte ristics10.2.2 Examp les of dam breachings10.2.3 Breach characteristics10.2.4 Singh s model for dam breach development

10.3 De Saint-Venant equations10.4 One-dimensional dam break flow

10.4.1 Rit ter solution10.4.2 Dressler s asym ptotic solution10.4.3 Pohle s 2D-ap proach10.4.4 Hu nt s asymptotic solution

10.5 Experimental approach10.5.1 Experim ental observ ations10.5.2 Horizontal smooth channel10.5.3 Sloping smoo th chann el

References

Subject Index

Author Index

Contents

243243244245245247248248248250250252

255255255255256257257259261262262263264264

264264266268269

27271272272272275276279281281282284286287287288296

303

305

314

dam hydraulic

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