Study On Numerical Simulations Of Hydrodynamics And Its Application To The Study On Sediment Movement In Coastal And Estuarine Waters

This paper carries out studies on the numerical simulations of hydrodynamics(tidal current, water wave and wave-induced nearshore current) and the resulting sediment movement in coastal and estuarine waters. For scientificaalness and effectiveness, convenience and practicality in engineering applications, on the basis of comprehensive and systematic summing-up and review on the studies of hydrodynamics and sediment movement in coastal and estuarine waters, in accordance of features of coastal and estuarine waters and the drawbacks of the previous numerical methods and through study and improvement in theory and numerical technique, multi-sets of practical mathematical models of hydrodynamics and sediment movement are set up, which are all verified with practical applications. Moreover, a number of practical techniques on irregular triangular grid are developed, and determining methods of a number of parameters in the sediment models are comprehensively presented. Practical applications show that the multi-sets of mathematical models can satisfy the present need for numerical simulations of hydrodynamics and sediment movement in coastal and estuarine waters conveniently and effectively. The main research achievements are as follows: 1.Based on linear component wave theory and wave direction spectrum theory, a governing equation for multi-directional irregular wave transformation in non-uniform current and rapidly-varying topography with the consideration of bottom friction and nonlinear dispersion effect is derived, and then a multi-directional irregular wave transformation mathematical model taking into account multi-factors such as nonlinear dispersion effect, rapidly varying topography, current, wave breaking, island, bottom friction, refraction, diffraction is set up by means of finite difference scheme, which is suitable for wave field computation of large sea area with complicated bottom topography in coastal and estuarine waters. 2.The governing equations of wave-induced nearshore current and wave radiation stress are improved, in which terms reflecting wave breaking effect are added, thus making them more reasonable in the surfzone. 3.With both rectangular grids and triangular grids, multi-sets of finite-difference mathematical models of 2-D tidal current, 2-D tidal current with wave, 2-D wave-induced nearshore current and 2-D sediment are set up. The 2-D tidal current model with wave and the above wave model with current constitute a coupled tidal current and wave mathematical model. 4.By using σcoordinate transformation technique and finite difference numerical method, 3-D tidal current and 3-D sediment mathematical models with both rectangular grids and triangular grids are set up. Besides having advantages from σcoordinate transformation, the 3-D tidal current model has another advantage that it can take vertically–averaged current speed as its open boundaries, which is very convenient for the model operation and for the nesting operations between 2-D and 3-D models. 5.A number of practical techniques on irregular triangular grids are developed. 6.Determining methods of a number of parameters in the sediment models and their value ranges are comprehensively presented.