Numerical Simulations Of Three Dimensional Suspendend Sediment Transport With Wave-current Co-existing And Its Application In Huanghe Delta

Coastal and estuary regions are such regions where the interaction between land and sea is obvious and the sediment becomes a big problem for coastal engineering. Coastal and estuary regions are characterized by intensive interaction between wave and current. Moreover, these regions are of great economic significance to mankind. Therefore, the simulation of sediment with wave and current as well as their mutual interactions in coastal and continental shelf waters has great economic value. In this dissertation, a three dimensional suspended sediment model is setup and is coupled with the combination of COHERENS and SWAN. In the end, a coupled hydrodynamic-sediment model is obtained and is adopted to simulate three dimensional current and suspended sediment of Huanghe delta. The damping function of suspended sediment on turbulence and the equilibrium assumption of turbulence are accounted for in coupled three dimensional hydrodynamic-sediment model. The turbulence energy expression of one equation turbulence close model k — ε is derived and adopted as the boundary condition of turbulence energy. Wave dependent surface drag coefficient, wave induced surface mixing length, wave-enhanced bottom stress and radiation stress are introduced into the coupled model and are analyzed through numerical experiments. Moreover, a bed model being able to stand for horizontal or vertical variant bed properties is setup in the present work, which is reasonable to the practical situation of field bed.The major contents in this dissertation are shown as following:I AS for hydrodynamic model COHERENS, the works of this dissertation are as follows: The introduction of the angle between current direction and wave propagation direction into COHERENS; Accounting for sediment damping function in turbulence close model; Abandon the well-known equilibrium between turbulence production and dissipation near the bottom and adopt the equilibrium assumption betweenturbulence production, dissipation and buoyancy induced destruction. According to the assumption, the expression of bottom boundary conditions for k - e is derived;> Accounting for the breaking wave induced surface mixing length in calculation of the mixing length;> Introduction of wave dependent surface drag coefficient;> Introduction of radiation stress;II Combine COHERENS and the third generation wave model SWAN and account for the influences of surface elevation and current velocity on wave calculation.III Setup and develop the numerical model of three dimension suspended sedimentwith wave and current co-existing;IV Discover the existence of three dimensional structures of shear front in Yellowdelta. The shear front of top and bottom layer show some obvious differences in tidal phase, duration and strength between each other, which can be attributed the difference of tidal phase and effects of river discharge.