Title Page
ABSTRACT
Contents
1. Introduction 15
1.1. Background 15
1.2. Objectives 18
2. Previous Studies on Desilting Basin 19
2.1. Literature Review 19
2.2. Design Principle 25
2.2.1. Types of Desilting Basins 25
2.2.2. Hydraulics in Desilting Basin 26
2.3. Design criteria of desander basin 29
2.3.1. Determining Size of Desander 29
2.3.2. Application of Criteria 32
2.3.3. Optimum Particle Size Selection 33
3. Physical Model Test 34
3.1. Model Setup 34
3.2. Model Laws and Scales 35
3.3. Measurements 37
3.3.1. Discharge Measurements 37
3.3.2. Measurement of Water Elevation 38
3.3.3. Velocity Measurements 38
3.3.4. Settling Basins 39
3.4. Modification to enhance performance 41
3.4.1. Divide Wall Extension 41
3.4.2. Pressurized Inlet Transition 43
3.5. Results of Combined Modifications 46
3.5.1. Plot of Measured Data 50
4. Numerical Analysis 64
4.1. Theoretical Background 64
4.1.1. General 64
4.1.2. Governing Equations 65
4.1.3. Turbulence Models 66
4.1.4. FAVOR and Grid Systems 68
4.1.5. Numerical Approximations 69
4.2. Comparison of Numerical and Physical Data 70
4.2.1. Numerical model setup 70
4.2.2. Results for Guide Wall 70
4.2.3. Discrepancy Ratio 71
4.3. Analysis of Flow Characteristics of Desander 80
4.3.1. General 80
4.3.2. Definition of Efficiency 80
4.3.3. Configuration of Model Setup 84
4.3.4. Effects of Inlet Pipe Diameter 87
4.3.5. Effects of Inlet Pipe Bottom Elevation 93
4.3.6. Effects of Lowering Slope (applying step) 95
4.3.7. Effects of Projection from End of Pipe to Step 97
4.3.8. Effect of Transition Length and Slope 100
4.3.9. Effect of Basin Length 104
4.3.10. Effect of Outlet Bottom Height 107
4.3.11. Effect of Outlet Bottom Level 109
4.3.12. Sensitivity of Each Design Parameter 111
4.3.13. Effect of Turbulence Kinetic Energy (TE) 113
4.3.14. Porous Plate Applicability 121
4.3.15. Required Settlement Length for Design Particle 124
5. Design Application 136
5.1. Design Flow of Underground-Type Desander 136
5.2. Application to UT1 HEP 139
5.2.1. Introduction of UT1 HEP 139
5.2.2. Design Procedure Application to UT1 HEP 146
6. Conclusions and Recommendations 147
1) Divide wall and guide wall 147
2) Comparison of numerical and physical model results 148
3) Application of newly proposed basin efficiency 148
4) Priority of parameters in desander design 148
5) Turbulence energy 149
6) Porous plate application 149
7) Design practice 149
8) Particle tracing 149
9) Future study 150
7. References 151
요지 157
Table 2-1. Maximum forward velocity for particle diameter 29
Table 2-2. Example dimensions of hydro-power projects 33
Table 3-1. Scale ratio according to Froude's model law 36
Table 3-2. Average velocities of dye in settling basins 39
Table 3-3. Velocities found using ADV 60
Table 4-1. Comparison of physical and numerical results for case 1 73
Table 4-2. Comparison of physical and numerical results for case 3 76
Table 4-3. Base case for numerical test 85
Table 4-4. Test cases of sensitivity analyses of parameters 86
Table 4-5. Test run cases for inlet tunnel diameter 88
Table 4-6. Boundary conditions 88
Table 4-7. Fluid properties of 15℃ water 88
Table 4-8. Run cases for inlet diameter 91
Table 4-9. Run cases for inlet pipe bottom level 93
Table 4-10. Run cases for application of steps 95
Table 4-11. Run cases for projection from pipe to step 97
Table 4-12. Run cases for transition length and slope 101
Table 4-13. Run cases for basin length 104
Table 4-14. Run cases for outlet bottom height 107
Table 4-15. Run cases for outlet bottom level 109
Table 4-16. Deviations of parameters in basin efficiency 111
Table 4-17. Cross-sectional velocity distribution 125
Table 4-18. Tracing particle starting from elevation of 1255.0 m 130
Table 4-19. Tracing particle starting from elevation of 1254.1 m 130
Table 4-20. Tracing particle starting from elevation of 1253.1 m 131
Table 4-21. Tracing particle starting from elevation of 1252.1 m 131
Table 4-22. Tracing particle starting from elevation of 1251.1 m 132
Table 4-23. Tracing particle starting from elevation of 1250.2 m 132
Table 4-24. Non-resuspension trajectory of particle starting from elevation of 1255.0 m 135
Table 5-1. Salient features of UT1 HEP 141
Figure 2-1. Schematic of desilting basin 27
Figure 2-2. Schematics of settling velocity 28
Figure 2-3. Fall velocities of spherical quartz in water and air from Rouse 30
Figure 2-4. Schematic drawing of underground-type desander 32
Figure 3-1. Plan of desilting basin 34
Figure 3-2. Profile of desilting basin 34
Figure 3-3. CD5-Box calibration curve 38
Figure 3-4. Longitudinal section view 40
Figure 3-5. Plan of divide wall upstream of trifurcation 42
Figure 3-6. Flow area ratios after introducing divide wall 42
Figure 3-7. Advance of dye after introducing divide wall 43
Figure 3-8. Advance of dye before modification of inlet 44
Figure 3-9. Original section without guide wall 45
Figure 3-10. Modified section with guide wall 45
Figure 3-11. Advance of dye with combined modification 46
Figure 3-12. Flow after transition in left basin with guide wall of 10 m 47
Figure 3-13. Flow after transition in right basin with guide wall of 10 m 47
Figure 3-14. Advance of dye after modification of inlet with 20-m guide wall 48
Figure 3-15. Longitudinal section of desander 48
Figure 3-16. Cross sections of desander 49
Figure 3-17. Case 1 (guide wall of 0 m)-longitudinal velocity 50
Figure 3-18. Case 2 (guide wall of 10 m)-longitudinal velocity 50
Figure 3-19. Case 3 (guide wall of 20 m)-longitudinal velocity 50
Figure 3-20. Velocity profiles in depth direction for case 1 52
Figure 3-21. Velocity profiles in depth direction for case 2 53
Figure 3-22. Velocity profiles in depth direction for case 3 54
Figure 3-23. Case 1: C 55
Figure 3-24. Case 1: D 55
Figure 3-25. Case 1: E 56
Figure 3-26. Case 1: F 56
Figure 3-27. Case 1: G 56
Figure 3-28. Case 1: H 56
Figure 3-29. Case 1: I 57
Figure 3-30. Case 2: D 57
Figure 3-31. Case 2: E 57
Figure 3-32. Case 2: F 57
Figure 3-33. Case 2: G 58
Figure 3-34. Case 2: H 58
Figure 3-35. Case 2: I 58
Figure 3-36. Case 3: E 58
Figure 3-37. Case 3: F 59
Figure 3-38. Case 3: G 59
Figure 3-39. Case 3: H 59
Figure 3-40. Case 3: I 59
Figure 4-1. Streamline results for case 1 71
Figure 4-2. Streamline results for case 3 71
Figure 4-3. Frequency over discrepancy ratio for case 1 79
Figure 4-4. Frequency over discrepancy ratio for case 3 79
Figure 4-5. Turbulent velocity profile in open channel 82
Figure 4-6. Velocity magnitude in 200-m-long ideal channel 83
Figure 4-7. Velocity profiles at x = 200 m 83
Figure 4-8. Configuration of desander 84
Figure 4-9. Planar view of desander 84
Figure 4-10. Stream line of desander 89
Figure 4-11. Longitudinal profiles for several inlet diameters 90
Figure 4-12. Efficiency results for inlet pipe diameter 92
Figure 4-13. Efficiency results for inlet pipe bottom elevation 94
Figure 4-14. Efficiency results for application of steps 96
Figure 4-15. Efficiency results for length from pipe to step 98
Figure 4-16. Combined efficiency results for length from pipe to step 99
Figure 4-17. Efficiency results for transition slope 102
Figure 4-18. Combined efficiency results for transition slope 103
Figure 4-19. Efficiency results for basin length 105
Figure 4-20. Combined efficiency results for basin length 106
Figure 4-21. Efficiency results for outlet bottom height 108
Figure 4-22. Efficiency results for outlet bottom level 110
Figure 4-23. Ranges of maximum and minimum efficiencies 112
Figure 4-24. Turbulence energy values for different basin lengths 114
Figure 4-25. Maximum turbulence energy values for different basin lengths 115
Figure 4-26. Turbulence energy distribution along ideal channel 116
Figure 4-27. TE distribution along desander 117
Figure 4-28. Turbulence energy values for different inlet diameters 117
Figure 4-29. Vertical variation in TE along basin 119
Figure 4-30. Schematic of porous plate installation 121
Figure 4-31. Turbulence energy values for different lengths of porous plates 122
Figure 4-32. Maximum TE values for different lengths of porous plates 123
Figure 4-33. Longitudinal and sectional measuring points 124
Figure 4-34. Velocity distribution of y-z plane 128
Figure 4-35. Particle trajectories calculated at different elevations 133
Figure 4-36. Potential areas of re-suspension 134
Figure 4-37. Trajectory of particle considering re-suspension area 135
Figure 5-1. Diagram of design process 138
Figure 5-2. Project location 139
Figure 5-3. Project layout 140
Figure 5-4. Headwork layout of UT1 HEP project 143