1. 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

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) Birkemeier (1985)
annul mean significant wave height + standard deviation
Birkemeier (1985)

6. cross-shore sediment transport
Madsen and Grant (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 ( ) 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

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

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

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

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

40. Recent study-1
Steady sheet-flow