Numerical Simulations On The Instability Of Alongshore Currents

Complicated hydraulic environment which will bring difficulty to studying diffusion and transport of the pollution is forced when alongshore currents are induced by the wave breaking in the near shore region.The shear instability of the alongshore currents add to the in shore environment new problem.The article contains the following contents according to the instability of the alongshore currents.Two-dimensional depth-averaged alongshore currents numerical model calculating the instability is built,calculation of the forces and discrete method of the governing equations domain of the model and the boundary conditions are given.Conceptual framework and instability of plane mixing layer and a determining method on the fluid are presented.Linear instability theory and a numerical approach obtaining the unstable modes of the alongshore currents are recommended.The numerical model of the alongshore current instability is validated,instability of alongshore currents is calculated under different averaged alongshore currents and longshore computational length and bottom friction.In addition,the results are compared with former researches.Instability of alongshore currents for regular and irregular waves on two plane beaches with slopes 1:100 and 1:40 in the laboratory are calculated with the model presented hereinbefore,and the results are contrasted with corresponding experimental data.The effect from the bottom fricton and longshore computational length and the lateral momentum mixing to the instability of the alongshore currents is dicussed.