Thạc Sĩ Cross-sectional Stability of a Two-inlet Bay System

VII
Table of Contents
PREFACE .III
ABSTRACT . V
TABLE OF CONTENTS VII
LIST OF FIGURES . XI
LIST OF TABLES XIII
CHAPTER 1 INTRODUCTION .1
CHAPTER 2 PROBLEM ANALYSIS .3
2.1 Introduction 3
2.2 One - inlet bay system .3
2.3 Two inlet bay system .4
2.4 Goal of this study .8
CHAPTER 3 MODEL FOR CROSS–SECTIONAL STABILITY .9
3.1 Principles of stability analysis 9
3.2 Classification of equilibrium flow curves. .11
3.2.1 Type A 11
3.2.2 Type B 12
3.2.3 Type C 12
3.2.4 Type D 13
3.2.5 Type E 15
3.3 Inlet-bay schematization 17
3.3.1 Two inlet bay system .17
3.3.2 Two inlet bay system with partition 18 VIII
CHAPTER 4 INLET HYDRODYNAMICS .19
4.1 Introduction 19
4.2 One-inlet bay system .19
4.3 Two-inlet bay system .22
4.4 Two-inlet bay system with partition 23
4.5 Verification of the solutions 24
CHAPTER 5 CALCULATIONS 27
5.1 Introduction 27
5.2 Reference situations 27
5.2.1 Two inlet bay system .27
5.2.2 Two inlet bay system with partition 28
5.2.3 Discussion 29
5.3 Symmetrical ocean tide conditions for both inlets 30
5.3.1 Variations with one parameter .30
5.3.2 Variations with two parameters 31
5.3.3 Discussion 31
5.4 Different ocean tide conditions for both inlets 32
5.4.1 Variations with one parameter .32
5.4.2 Variations with two parameters 39
5.4.3 Discussion 39
5.5 Phase differences inside the bay . 40
5.5.1 Variations with one parameter .40
5.5.2 Variations with two parameters 48
5.5.3 Discussion 49
CHAPTER 6 APPLICATION TO THE TAM GIANG – CAU HAI LAGOON, VIETNAM 51
6.1 Introduction 51
6.2 Description of the system .52
6.3 Objectives 53
6.3.1 Simulation excluding the Hoa Duan inlet .54
6.3.2 Simulation excluding the Thuan An inlet 56
6.3.3 Simulations excluding the Tu Hien inlet .57
CHAPTER 7 CONCLUSIONS AND RECOMMENDATIONS 59
REFERENCES 61
APPENDICES .1 IX
APPENDIX A SOLUTION FOR A TWO INLET BAY SYSTEM .2
APPENDIX B SOLUTION FOR A TWO INLET BAY SYSTEM WITH PARTITION .6
APPENDIX C CALCULATIONS ON THE TWO INLET BAY SYSTEM .10
C.1. Reference situation 10
C.2. Variations in tidal wave 11
C.2.1. Tidal Period 11
C.2.2. Tidal amplitude .12
C.2.3. Short lengths combined with tidal amplitude .13
C.2.4. Tidal amplitude difference 14
C.2.5. Short lengths combined with an amplitude difference .15
C.2.6. Tide imbalance at higher tidal ranges 16
C.2.7. Phase lag .17
C.2.8. Tidal difference in both amplitude and phase 18
C.3. Inlet characteristics 19
C.3.1. Short Inlets .19
C.3.2. Longer inlets .20
C.3.3. Differences in inlet length .21
C.3.4. Friction .22
APPENDIX D CALCULATIONS ON THE TWO INLET BAY SYSTEM WITH PARTITION .24
D.1. Reference situation 24
D.2. Variations in tide and inlet parameters 25
D.2.1. Tidal amplitude .25
D.2.2. Short lengths combined with tidal amplitude .26
D.2.3. Amplitude difference 27
D.2.4. Short lengths combined with amplitude difference 28
D.2.5. Stability conditions for increasing tidal difference 29
D.2.6. Stability conditions for increasing tidal difference (big partition) 30
D.2.7. Short Inlets .31
D.3. Variations with partition inlet 32
D.3.1. Large cross-sectional area .32
D.3.2. Larger cross-sectional area .33
D.3.3. Small cross-sectional area .34
D.3.4. Long length 35
D.3.5. Sensitivity of partition inlet . 36
D.4. Variations with bay ratio .41
D.4.1. Bay Ratio 41
D.4.2. Bay Ratio with small partition inlets .42
D.4.3. Bay Ratio with tidal amplitude difference .49
APPENDIX E INLET AND BAY PARAMETERS OF THE TAM GIANG - CAU HAI LAGOON,
VIETNAM .54 X
APPENDIX F SIMULATIONS ON THE TAM GIANG - CAU HAI LAGOON, VIETNAM 58
F.1. Hoa Duan inlet closed, with partition .58
F.2. Thuan An inlet closed, with partition 61
F.3. Tu Hien inlet closed .64
F.4. Tu Hien inlet closed with partition 67 XI
List of Figures
Figure 2.1. Closure curve of a stable tidal inlet 4
Figure 2.2. Closure surface of Inlet 1 plotted against Inlet 2 5
Figure 2.3. Equilibrium flow curve of Inlet 1, plotted against Inlet 2 .5
Figure 2.4. Closure surface of Inlet 2 plotted against Inlet 1 6
Figure 2.5. Equilibrium flow curve of Inlet 2, plotted against Inlet 1 .6
Figure 2.6. Possible configurations of equilibrium flow areas 7
Figure 3.1. Cross-sectional area – Tidal Prism Relationship for inlets in the U.S.A 10
Figure 3.2. Type A flow curve .11
Figure 3.3. Type B flow curve .12
Figure 3.4. Type C flow curve. .13
Figure 3.5. Type D flow curve. .13
Figure 3.6. Examples of instability in type D. .14
Figure 3.7. Type E flow curve .15
Figure 3.8. Examples of stability in Type E 16
Figure 3.9. Two - inlet bay system. 17
Figure 3.10. Two inlet bay system with partition. .18
Figure 4.1. Triangular cross section .20
Figure 4.2. Closure scenario. .20
Figure 4.3. Top view of Matagorda Bay. In the centre below is Pass Cavallo; a little to the north,
splitting the barrier, is Matagorda Inlet .24
Figure 4.4. Equilibrium flow curves for Pass Cavallo and Matagorda Inlet (van de Kreeke, 1990). 25
Figure 4.5. Equilibrium flow curves for Pass Cavallo and Matagorda inlet, calculated by the two
inlet bay system model. .26
Figure 5.1. Equilibrium flow curve for the two inlet bay system. 28
Figure 5.2. Equilibrium flow curve for the two inlet bay system with the partition 29
Figure 5.3. Changes in the equilibrium flow curves around ĥ 01 = 0.59 m. 34
Figure 5.4. Equilibrium flow curves at higher tide differences 35
Figure 5.5. Closure surfaces of Inlets 1 and 2 at increasing tide differences. .36
Figure 5.6. Equilibrium flow curves at increasing phase differences. 38
Figure 5.7. E-type flow curve as a result of tide difference 40
Figure 5.8. E-type flow curve, caused by a smaller partition inlet 41
Figure 5.9. Limit E-type condition at A3 = 2900 m2 and a main tide of 0.50 m. 42
Figure 5.10. Limit E-type condition at A3 = 6500 m2 and a main tide of 1.00 m. 43
Figure 5.11. Limit E-type condition at A3 = 10400 m2 and a main tide of 1.50 m. 43
Figure 5.12. Limit E-type condition at A3 = 14000 m2 and a main tide of 2.00 m. 44
Figure 5.13. Limit E-type condition at A3 = 18500 m2 and a main tide of 2.50 m. 44
Figure 5.14. Water level amplitude differences inside the bay at a bay ratio of 1 (a), 2 (b) and 10 (c).
.46
Figure 5.15. Phase level differences inside the bay at a bay ratio of 1 (a), 2 (b) and 10 (c). 47
Figure 5.16. Equilibrium flow curve at ĥ 01 = 0.56 m. 48
Figure 6.1. Map of the Tam Giang – Cau Hai lagoon system 51
Figure 6.2. Overview of lagoon areas and inlets with cross-sectional profiles. .52
Figure 6.3. Model of the lagoon system .53
Figure 6.4. 3D image of the closure curve of Thuan An inlet (cross section A 1 ), plotted against Tu
Hien inlet (cross section A 2 ) .54
Figure 6.5. 3D image of the closure curve of Tu Hien inlet (cross section A 2 ), plotted against Thuan
An inlet (cross section A 1 ) 54
Figure 6.6. Equilibrium flow curves for Thuan An inlet and Tu Hien inlet, at ∆ φ = 0.18 π rad 55 XII
Figure 6.7. Equilibrium flow curves for Hoa Duan inlet and Tu Hien inlet, at ∆ φ = 0.16 π rad 56
Figure 6.8. Equilibrium flow curves for Thuan an and Hoa Duan inlet, at ∆ φ = 0.02 π rad .57
Figure 6.9. Equilibrium flow curves for Thuan An and Hoa Duan inlet, at ∆ φ = 0.02 π rad 58
Figure 6.10. Closure surfaces for Thuan An inlet (left) and Hoa Duan inlet (right) 58
Figure D.1. Flow curves for amplitudes at inlet 1 of 0.50 m (green), 0.53 m (blue), 0.56 m (red) and
0.59 m (magenta) .29
Figure D.2. Flow curves for amplitudes at Inlet 1 of 0.50 m (green), 0.53 m (blue), 0.56 m (red) and
0.59 m (magenta) .30
Figure D.3. Equilibrium flow curves for A b1 /A b2 values of 0.1 (red), 1 (green) and 10 (blue) 41
Figure D.4. Equilibrium flow curves for bay area ratios of 0.10 (a), 1 (b) and 10 (c) 49
Figure D.5. Equilibrium flow curves for bay area ratios of 0.10 (a), 1 (b) and 10 (c) 50
Figure D.6. Equilibrium flow curves for bay area ratios of 0.10 (a), 1 (b) and 10 (c) 51
Figure D.7. Equilibrium flow curves for bay area ratios of 0.10 (a), 1 (b) and 10 (c) 52
Figure E.1. Map of the lagoon system with depth profiles 54
Figure F.1. Simulation with φ 2 = 0.18 π rad .58
Figure F.2. Simulation with φ 2 = 0.0 .59
Figure F.3. Simulation with φ 2 = -0.18 π rad 60
Figure F.4. Simulation with φ 2 = 0.16 π rad .61
Figure F.5. Simulation with φ 2 = 0.0 .62
Figure F.6. Simulation with φ 2 = -0.16 π rad 63
Figure F.7. Simulation with φ 2 = 0.02 π rad .64
Figure F.8. Simulation with φ 2 = 0.0 .65
Figure F.9. Simulation with φ 2 = -0.02 π rad 66
Figure F.10. Simulation with φ 2 = 0.02 π rad .67
Figure F.11. Simulation with φ 2 = 0.0 .68
Figure F.12. Simulation with φ 2 = -0.02 π rad 69
List of Tables
Table 4.1. Values of parameters used in Matagorda Bay .25
Table 5.1. Reference values. 28
Table 5.2. Reference values. 29
Table 5.3. Summary of simulation results with symmetrical tide conditions .31
Table 5.4. Observed variations in tide, limit flow areas and flow types. .35
Table 5.5. E-type conditions at different tide levels. .37
Table 5.6. Instability at higher phase differences. 37
Table 5.7. Summary of simulation results .39
Table 5.8. Summation of flow types at different partition cross sections on a tide of 0.50 m .42
Table 5.9. Summation of flow types at different partition cross sections on a tide of 1.00 m .43
Table 5.10. Summation of flow types at different partition cross sections on a tide of 1.50 m .44
Table 5.11. Ratio between tidal amplitudes and partition cross-sections .45
Table 5.12. Summary of flow types at different simulations. 49
Table D.1. Equilibrium cross-sectional values for different tidal amplitudes at inlet 1. .29
Table D.2. Equilibrium cross-sectional values for different tidal amplitudes at inlet 1. .30
Table D.3. Equilibrium cross-sectional values for different bay area ratios. .41
Table D.4. Equilibrium cross-sectional values for different bay area ratios. .42
Table D.5. Equilibrium cross-sectional values for different bay area ratios. .45
Table D.6. Equilibrium cross-sectional values for different bay area ratios. .47
Table D.7. Equilibrium cross-sectional values for different bay area ratios. .49
Table D.8. Equilibrium cross-sectional values for different bay area ratios. .50
Table D.9. Equilibrium cross-sectional values for different bay area ratios. .51
Table D.10 Equilibrium cross-sectional values for different bay area ratios. .52
Table E.1. Average inlet characteristics of the Tam Giang-Cau Hai lagoon system (Lam, 2002) 55
Table E.2. Inlet parameters of the Tam Giang-Cau Hai lagoon system. 56