NUMERICAL-SIMULATION OF 3D QUASI-HYDROSTATIC, FREE-SURFACE FLOWS

Numerical models that assume hydrostatic pressure are usually sufficie ntly accurate for applications in civil engineering where the vertical component of the velocity is relatively small. Nevertheless, the vert ical momentum, and, hence, the nonhydrostatic pressure component, cann ot be neglected when the bottom topography of the domain changes abrup tly as in cases of short waves, or when the flow is determined by stro ng density gradients. In this paper a numerical method for the three-d imensional (3D) quasi-hydrostatic, free-surface flows is outlined. The governing equations are the Reynolds-averaged Navier-Stokes equations with the pressure decomposed into the sum of a hydrostatic component and a hydrodynamic component. The momentum equations, the incompressib ility condition, and the equation for the free surface are integrated by a time-splitting method in such a fashion that the resulting numeri cal solution is mass conservative and stable at a minimal computationa l cost. Several applications serve to illustrate the effect of the dev iation from the hydrostatic pressure.