The Initialization of Vortical Free-Surface Flows

Numerical simulations of vortical free-surface flows are prone to developing spurious high-frequency dispersive waves unless the flow field is given sufficient time to adjust. At low Froude numbers, the high-frequency waves obscure the true hydrostatic balance of the free-surface elevation with the component of the pressure that is induced by the vortical portion of the flow. The high-frequency waves must be eliminated for remote sensing applications because otherwise the roughening of the free surface and the predicted radar backscatter will be incorrect. A procedure is developed for reducing the initial impulse of the pressure and the subsequent generation of high-frequency waves. Numerical simulations of whirls illustrate the effectiveness of the procedure. The pressure field of the whirls forms dimples on the free surface.