Title Page
Abstract
요약
Contents
Nomenclature 18
Subscripts 19
Superscripts 19
Greek Symbols 20
CHAPTER 1. Introduction 21
1.1. Background 21
1.1.1. Current Status and Ocean Energy Trends 21
1.1.2. Types and Features of Hydropower 24
1.2. Development of Water Wheel Turbine 27
1.2.1. Water Turbine Classifications 27
1.2.2. Water Wheel Turbine 29
1.3. Study Aims and Objectives 35
CHAPTER 2. Theory and Numerical Approach 36
2.1. Theory 36
2.2. Numerical Approach 40
2.2.1. Computational Fluid Dynamics 40
2.2.2. Governing Equations of Fluid Motion 41
2.2.3. Turbulence and Near-Wall Modelling 45
2.2.4. Analytical Solutions 47
2.2.5. Uncertainty and Errors in CFD Simulation 48
CHAPTER 3. Experimental Apparatus and Procedure 50
3.1. Experimental Apparatus 50
3.2. Test Procedure 57
CHAPTER 4. Computational Method 60
4.1. Meshing Strategy 60
4.2. Calculation Domain and Boundary Conditions 61
4.2.1. Calculation Domain 61
4.2.2. Boundary Conditions 62
CHAPTER 5. Computational and Experimental Results 64
5.1. Effect of Blade Numbers 64
5.1.1. CFD Benchmarking 64
5.1.2. Evaluation of Turbine Performance 66
5.1.3. Analysis of Flow Fields and Velocity Triangles 71
5.2. Effect of Blade Angles of Inclination 85
5.2.1. Performance Curves 85
5.2.2. Analysis of Flow Characteristics 88
5.3. Effect of Bottom Clearance 96
5.3.1. Performance Curves 96
5.3.2. Flow Visualizations 99
5.4. Effect of Blade Shapes 106
5.4.1. Performance Curves 106
5.4.2. Comparison of Flow Fields 111
5.5. Discussion 115
CHAPTER 6. Concluding Remarks 118
Future Work 120
Citation to Previously Published Work 122
References 123
Table 3.1. General turbine design parameters 51
Table 3.2. Experimental equipment specifications 56
Table 3.3. Specifications for turbines with different numbers of blades 57
Table 3.4. Specifications for turbines with different bottom clearances 58
Table 3.5. Specifications for turbines with different blade angles of inclination 58
Table 4.1. Calculation domain setups 63
Table 4.2. Boundary conditions 63
Table 5.1. Specification of test runners by Nishi et al. 108
Fig. 1.1. World energy consumption by energy source, 1990-2040 22
Fig. 1.2. Estimated renewable energy share of total final energy... 23
Fig. 1.3. An illustration of a conventional dammed-hydro facility 25
Fig. 1.4. An illustration of a tidal turbine extracting energy from tidal streams 26
Fig. 1.5. Kaplan turbine runner 28
Fig. 1.6. Overshot water wheel 29
Fig. 1.7. Breast-shot water wheel 30
Fig. 1.8. Undershot water wheel 30
Fig. 1.9. Stream waterwheel designed by Batten et al. 32
Fig. 2.1. Theory of a stream water wheel 37
Fig. 2.2. Definition of the blade movement 38
Fig. 2.3. "Three Dimensions" of fluid dynamics 40
Fig. 2.4. Example of CFD application 41
Fig. 2.5. Near-wall region illustration 46
Fig. 3.1. Test model of water wheel turbine 51
Fig. 3.2. Schematic diagram of experimental setup 52
Fig. 3.3. Working principle of Pitot tube 54
Fig. 3.4. Differential pressure flowmeter 54
Fig. 3.5. Electromagnetic brake 55
Fig. 3.6. An illustration of bottom clearance 57
Fig. 3.7. Differing blade inclined angles 58
Fig. 4.1. Calculation domain 61
Fig. 5.1. Mesh dependence test 64
Fig. 5.2. Fine numerical grids of the wheel domain 65
Fig. 5.3. Turbulence model dependence test 66
Fig. 5.4. Comparison of efficiency among different blade numbers 68
Fig. 5.5. Torque variation in a cycle 69
Fig. 5.6. Difference in water level, Δd between the upstream and downstream... 70
Fig. 5.7. Water volume fractions at the wheel's outer circumference 72
Fig. 5.8. Velocity triangles at the wheel inlet and outlet 74
Fig. 5.9. Comparison of absolute velocity v at outer circumference (TSR 0.4) 75
Fig. 5.10. Distribution of velocity vectors at rotational angle θ=0˚ 78
Fig. 5.11. Distribution of velocity vectors at rotational angle θ=30˚ 79
Fig. 5.12. Distribution of velocity vectors at rotational angle θ=60˚ 80
Fig. 5.13. Distribution of velocity vectors at rotational angle θ=90˚ 81
Fig. 5.14. Reference plane of water level 82
Fig. 5.15. Comparison of velocity vectors at different tip-speed ratios 83
Fig. 5.16. Comparison of power coefficient among all types of blade angles 86
Fig. 5.17. Comparison of torque among all types of blade angles 87
Fig. 5.18. Comparison of water volume fraction at the wheel's outer circumference... 90
Fig. 5.19. Comparison of absolute velocity v at outer circumference (TSR 0.4) 91
Fig. 5.20. Reference planes in depthwise direction for flow analysis 92
Fig. 5.21. Velocity vectors and contours at 0.15m depth 93
Fig. 5.22. Velocity vectors and contours at 0.35m depth 94
Fig. 5.23. Performance curves of different bottom clearances(ε) 98
Fig. 5.24. Velocity contours for different bottom clearances 100
Fig. 5.25. Pressure contours for different bottom clearances 102
Fig. 5.26. Distribution of velocity vectors for different bottom clearances 104
Fig. 5.27. Test runner of the turbine designed by Nishi et al. 106
Fig. 5.28. Experimental apparatus for the study by Nishi et al. 107
Fig. 5.29. Three types of blade shape used for the present study 108
Fig. 5.30. Performance curves of different blade shapes 111
Fig. 5.31. Velocity vectors at middle plane along the channel 113
Fig. 5.32. Visualization results in an experiment by Nishi et al. 114
Fig. 5.33. Absolute velocity vectors in computation by Nishi et al. 114