Simulations of nonlinear waves generated by an air-cushion vehicle

Abstract

One major area of interest in air-cushion vehicle (ACV) hydrodynamics is ACV-generated waves. However, the nonlinear effects of varying cushion pressures on the wake system remain unclear. This study presents a fast time-domain method that simulates nonlinear waves. The paper uses a pressure distribution to represent the ACV, models the nonlinear waves by the high-order spectral method, and saves computational effort with damping and domain reconstruction techniques. We simulate the nonlinear waves generated by a constant-speed/accelerating ACV in calm water and by ACV in regular waves, and compare our time-domain results with experimental, CFD, and perturbation theoretical ones. The results show that the nonlinear effects are more pronounced in shallow water and low-speed cases. In the constant-speed case, the maximum wave drag predicted by the nonlinear method is lower than the linear prediction; in the accelerating case, the nonlinear method shows a slight decrease in the Froude number when the resistance reaches the maximum during acceleration. For ACV in waves, nonlinear simulations show a second-order wave component resulting from the interaction between the air cushion and incident waves. This component has little effect on wave force but does contribute to the near-field wave pattern.