Theoretical Research Of Sediment Transport By Combined Tide Currents And Waves And Its Mathematical Model

In this paper, the theoretical research has been done about the mechanism of sediment transport by combined tide—currents and waves, and on this base, a set of tide—currents and waves' sediment transport mathematical model has been founded and which can be applied to engineering practice directly.According to the differences among physical scales about tide-current, wave and turbulence in nearshore zone and estuary, from Navier—Stokes equations and transport equation in fluid mechanics, the flow field and sediment diffusion equations are deduced by using Reynold's decomposition method, then through simplification, the shallow water current equations under the effecting of waves and the shallow water wave equations under the effecting of variance of tide level and velocity are obtained. In order to express the effect of turbulence, the dynamics eddy viscosity and sediment diffusivity coefficients are determined by solving K—ε turbulence model equations. In order to simulate the combined effects of tide—currents and waves in large area, the equations of wave ray and it's separation factor under the effects of flow velocity and tide level variance are first set up completely, and all around parameters of wave in this situation have aslo been obtained, which make the computing of combined tide—currents and waves carry out successefully.During solving sediment transport equation, by inducting the critical conditions for inception of suspended sediments and considering the random character of pulsation in the near—bed turbulence, the probability and statistics method is adopted in this paper to determine the quantities of suspended sediment picked up from and deposited on the bed by flow and gravity, which represent the exchanges of near-bed suspended sediment, then we use them as the source and sink terms to work out sediment diffusive equation and accomplish computations of the nonequilibrium sediment transport under joint effects of tide-currents and waves.According to the difference of sediment transportation by the single wave or wave current and the unidirect flow, two key factors are mainly grasped to consider the influ-...