Threshold condition of sand praticles under co-directional combined wave-and-current flow

Knowledge about the movement of sediment on the sea bed is highly important for the design of coastal structures and dredged navigation channels. In many cases sediment on the sea bed is moved by the combined influence of waves and currents. But so far the work done on the threshold condition of sediment movement under combined flow is rather limited because of its complex turbulence structure. In the present report some results obtained by laboratory flume tests have been given. Experiments have been carried out on rippled and flat beds with five different sizes of sand.