A CRITERION FOR THE INITIATION OF SEDIMENT MOVEMENT UNDER OSCILLATORY WAVES

摘要

In regard to the sediment transport caused by oscillatory waves, the first problem is tornpredict the threshold of sediment movement. Many researchers suggest that the Shieldsrncriterion obtained under unidirectional steady flows should be applicable to the onset ofrnsediment movement under oscillatory unsteady flows. However, the general trend of the datarnobtained under oscillatory flow conditions indicates that the critical value of the Shieldsrnparameters in the transition regime of laminar-turbulent flows are all above the Shields curverndetermined under unidirectional steady flow experiments. It is obvious that this difference isrnsystematic and cannot be attributed to individual differences in determining just when initialrnsediment movement occurs. In this paper, through a better analysis of the Shields curve andrnwave boundary layers, a new criterion curve, which can predict the threshold of sedimentrnunder wave action, is given. It shows satisfactory agreement with the experimental data.