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Cross-shore sediment transport

Cross-shore sediment transport. Chang Hsien Kuo. 國立交通大學土木工程學系 中華民國 102 年 5 月 9 日. cross- and long-shore sediment. beach profile vs. cross-shore sediment . beach profile vs. cross-shore sediment. depth of closure. Hallermerier (1978, 1981).

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Cross-shore sediment transport

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  1. Cross-shore sediment transport Chang HsienKuo 國立交通大學土木工程學系 中華民國102年5月9日

  2. cross- and long-shore sediment

  3. beach profile vs. cross-shore sediment

  4. beach profile vs. cross-shore sediment

  5. depth of closure Hallermerier (1978, 1981) annul mean significant wave height + standard deviation Birkemeier (1985)

  6. cross-shore sediment transport Madsen andGrant (1976): sediment transport for half wave period Watanabe et al. (1980): net sediment transport

  7. cross-shore sediment transport Sunamura (1982): Dominant sediment transport

  8. Bar formation Keulegan (1945)

  9. Bar formation Six types of longshore bars

  10. Bar formation Keulegan (1945)

  11. Bar formation Keulegan ratio=ht/hc ~1.69

  12. Bar formation Nayak’s criterion for longshore bars: Wave steepness (H/L) vs. wave height (H/h)

  13. Bar formation Standing wave and wave reflection

  14. Bar formation Partterns of secondary currents associated with different types of three dimensional longshore bar

  15. Beach cusp Beach cusps were first described by Palmer (1834)

  16. Beach cusp Cusp spacing is about one-half the wavelength of edge waves

  17. transverse sand bars

  18. transverse sand bars Ten years (1987-1996) of time exposure vidieo images of nearshore region at Duck, NC were used to study transverse sand bars.

  19. transverse sand bars Transverse bar spacing : mean longshore current and beach slope Komar (1998)

  20. transverse sand bars Predicted values were much less than the measured values

  21. Bed shear stress

  22. Bed shear stress

  23. Bed shear stress Soulsby, 1997: free stream velocity

  24. Bed shear stress Nielsen, 2002: shear velocity

  25. Bed shear stress Dick and Sleath, 1991: Momentum-integral method Sedimment/fluid mixture Dixen at al., 2008: Log-fit method (Law of the wall) The velocity profile can be approximated by a logrithmic function

  26. Bed shear stress Phase lag fluctuation

  27. Application to predict sand transport rate Nielsen, 2006: Bedload formulation Momentum integral method Symbols : tests Top: skewness of shear stress Bottom: phase lead of shear stress to free stream velocity

  28. Bed shear stress Four kinds of formulas for shear velocity

  29. Recent study-1 Net transport rate : velocity-load equation

  30. Recent study-1 Watanabe and Sato, 2004: Half-wave cycle

  31. Recent study-1 Shields parameter

  32. Recent study-1 Wave-current friction factor (Ribberink, 1998)

  33. Recent study-1 Sediment load between half cycles: Phase lag parameter Phase lag parameter

  34. Recent study-1

  35. Recent study-1 For velocity-skewed oscillatory sheet flows with d > 0.2mm Data: 32 Goodness: R2:0.78 Fac2%:97% Fac5%:100%

  36. Recent study-1 For acceleration-skewed oscillatory sheet flows with d > 0.2mm Data: 32 Goodness: R2:0.87 Fac2%:84% Fac5%:97%

  37. Recent study-1 For oscillatory sheet flows with d < 0.2mm Data: 29 Goodness: R2:0.80 Fac2%:86% Fac5%:93%

  38. Recent study-1 For oscillatory sheet flows over rippled bed Data: 50 Goodness: R2:0.65 Fac2%:62% Fac5%:89%

  39. Recent study-1 For oscillatory sheet flows with colinear currents Data: 50 Goodness: R2:0.84 Fac2%:70% Fac5%:86%

  40. Recent study-1 Steady sheet-flow

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