Title Page
Abstract
Contents
Nomenclature 19
Subscripts 20
Superscripts 20
Greek Symbols 21
CHAPTER 1. Introduction 22
1.1. Background 22
1.1.1. Current Status and Ocean Energy Trends 22
1.1.2. Types and Features of Hydropower 25
1.2. Development of Water Wheel Turbine 28
1.2.1. Water Turbine Classifications 28
1.2.2. Water Wheel Turbine 30
1.3. Study Aims and Objective 36
CHAPTER 2. Theory and Numerical Approach 37
2.1. Theory 37
2.2. Numerical Approach 41
2.2.1. Computational Fluid Dynamics 41
2.2.2. Governing Equations of Fluid Motion 42
2.2.3. Turbulence and Near-Wall Modelling 46
2.2.4. Analytical Solutions 48
2.2.5. Uncertainty and Errors in CFD Simulation 49
CHAPTER 3. Experimental Apparatus and Procedure 51
3.1. Experimental Apparatus 51
3.2. Test Procedure 58
CHAPTER 4. Computational Method 61
4.1. Meshing Strategy 61
4.2. Calculation Domain and Boundary Conditions 62
4.2.1. Calculation Domain 62
4.2.2. Boundary Conditions 63
CHAPTER 5. Computational and Experimental Results 65
5.1. Effect of Blade Numbers 65
5.1.1. CFD Benchmarking 65
5.1.2. Evaluation of Turbine Performance 67
5.1.3. Analysis of Flow Fields and Velocity Triangles 72
5.2. Effect of Blade Angles of Inclination 86
5.2.1. Performance Curves 86
5.2.2. Analysis of Flow Characteristics 89
5.3. Effect of Bottom Clearance 97
5.3.1. Performance Curves 97
5.3.2. Flow Visualizations 100
5.4. Effect of Blade Shapes 107
5.4.1. Performance Curves 107
5.4.2. Comparison of Flow Fields 112
5.5. Discussion 116
CHAPTER 6. Concluding Remarks 119
Future Work 121
Citation to Previously Published Work 123
References 124
Table 3.1. General turbine design parameters 52
Table 3.2. Experimental equipment specifications 57
Table 3.3. Specifications for turbines with different numbers of blades 58
Table 3.4. Specifications for turbines with different bottom clearances 59
Table 3.5. Specifications for turbines with different blade angles of inclination 59
Table 4.1. Calculation domain setups 64
Table 4.2. Boundary conditions 64
Table 5.1. Specification of test runners by Nishi et al. 109
Fig. 1.1. World energy consumption by energy source, 1990-2040 23
Fig. 1.2. Estimated renewable energy share of total final energy... 24
Fig. 1.3. An illustration of a conventional dammed-hydro facility 26
Fig. 1.4. An illustration of a tidal turbine extracting energy from tidal streams 27
Fig. 1.5. Kaplan turbine runner 29
Fig. 1.6. Overshot water wheel 30
Fig. 1.7. Breast-shot water wheel 31
Fig. 1.8. Undershot water wheel 31
Fig. 1.9. Stream waterwheel designed by Batten et al. 33
Fig. 2.1. Theory of a stream water wheel 38
Fig. 2.2. Definition of the blade movement 39
Fig. 2.3. "Three Dimensions" of fluid dynamics 41
Fig. 2.4. Example of CFD application 42
Fig. 2.5. Near-wall region illustration 47
Fig. 3.1. Test model of water wheel turbine 52
Fig. 3.2. Schematic diagram of experimental setup 53
Fig. 3.3. Working principle of Pitot tube 55
Fig. 3.4. Differential pressure flowmeter 55
Fig. 3.5. Electromagnetic brake 56
Fig. 3.6. An illustration of bottom clearance 58
Fig. 3.7. Differing blade inclined angles 59
Fig. 4.1. Calculation domain 62
Fig. 5.1. Mesh dependence test 65
Fig. 5.2. Fine numerical grids of the wheel domain 66
Fig. 5.3. Turbulence model dependence test 67
Fig. 5.4. Comparison of efficiency among different blade numbers 69
Fig. 5.5. Torque variation in a cycle 70
Fig. 5.6. Difference in water level, △d between the upstream and downstream... 71
Fig. 5.7. Water volume fractions at the wheel's outer circumference 73
Fig. 5.8. Velocity triangles at the wheel inlet and outlet 75
Fig. 5.9. Comparison of absolute velocity v at outer circumference (TSR 0.4) 76
Fig. 5.10. Distribution of velocity vectors at rotational angle θ=0˚ 79
Fig. 5.11. Distribution of velocity vectors at rotational angle θ=30˚ 80
Fig. 5.12. Distribution of velocity vectors at rotational angle θ=60˚ 81
Fig. 5.13. Distribution of velocity vectors at rotational angle θ=90˚ 82
Fig. 5.14. Reference plane of water level 83
Fig. 5.15. Comparison of velocity vectors at different tip-speed ratios 84
Fig. 5.16. Comparison of power coefficient among all types of blade angles 87
Fig. 5.17. Comparison of torque among all types of blade angles 88
Fig. 5.18. Comparison of water volume fraction at the wheel's outer circumference 91
Fig. 5.19. Comparison of absolute velocity v at outer circumference (TSR 0.4)(이미지참조) 92
Fig. 5.20. Reference planes in depthwise direction for flow analysis 93
Fig. 5.21. Velocity vectors and contours at 0.15m depth 94
Fig. 5.22. Velocity vectors and contours at 0.35m depth 95
Fig. 5.23. Performance curves of different bottom clearances (ε) 99
Fig. 5.24. Velocity contours for different bottom clearances 101
Fig. 5.25. Pressure contours for different bottom clearances 103
Fig. 5.26. Distribution of velocity vectors for different bottom clearances 105
Fig. 5.27. Test runner of the turbine designed by Nishi et al. 107
Fig. 5.28. Experimental apparatus for the study by Nishi et al. 108
Fig. 5.29. Three types of blade shape used for the present study 109
Fig. 5.30. Performance curves of different blade shapes 112
Fig. 5.31. Velocity vectors at middle plane along the channel 114
Fig. 5.32. Visualization results in an experiment by Nishi et al. 115
Fig. 5.33. Visualization results in computation by Nishi et al. 115