A LAYER-INTEGRATED NUMERICAL MODEL OF LONGSHORE CURRENT FOR A VERTICAL PLANE

摘要

Details are given of the refinement and application of a three-dimensional layer-integrated numerical model of longshore currents due to water waves. The mode splitting strategy has been used in the numerical scheme. The depth-integrated 2-D equations are first solved, using the alternating direction implicit (ADI) algorithm with the depth mean velocity being obtained from integrating the layer mean velocity. The layer-integrated 3-D equations are then solved to obtain the vertical distributions of the flow velocities. In order to calculate 3-D wave-induced current, the critical structure of radiation stress must be given. The traditional concept of radiation stress in water waves is used to its vertical profile in a new technical way. A relatively simple two-layer mixing turbulence model has been used to calculate the vertical eddy viscosity. The spatial variation of wave height, required to determine the gradient of the radiation stress, is modeled using to regular waves. We are compared the results obtained by the model for longshore current over a slightly modified plane beach. The profile of mean sea level for the laboratory experiment shown the good agreement between the values of the set-up and set-down. Wave-induced current of the vertical current occur strong vertical currents. Inside the surf zone, the currents are offshore along the seabed, and onshore directions at the water surface. Results of the present model are shown by the good agreement with the theory prediction and laboratory experiment.