密度成層領域に入射する表面波の非線形数値計算

抄録

This paper describes propagation of nonlinear water waves through a density-stratified fluid. The governing equations for a multilayer fluid system have been derived by vertical integration in each fluid layer with nonlinear boundary conditions satisfied on the interfaces. These equations, which can treat fluid density distribution inside each layer, are also applicable to compressible fluid motion with additional sets of equations concerning fluid density and pressure. Numerical computation was performed for surface and internal long waves in the vertical section using the simplified set which consists of the continuity equations and Bernoulli's equations for incompressible fluids having horizontally distributed density. The surface and internal waves progressing through the density stratified region, where the lower layer water is heavier than the upper, are simulated and the changing rates of wave height areobtained. The wave profiles change in space and time because of energy transfer between the surface and internal waves, which repeat transmission and reflection through the density stratified region, resulting in generating longer and shorter period waves.