Numerical Simulation of Water Entry Process of Trans-Medium Vehicles

The trans-medium water entry process of vehicles is often accompanied by multiphase flow, cavitation, phase change, and turbulence instability, which not only heighten the complexity of the flow field, but also render the forces highly unsteady and nonlinear. A numerical model for the water entry process of vehicles was developed. The volume of fluid(VOF) model was employed to capture the gas-liquid interface, and the Schnerr-Sauer model was utilized to describe the cavitation that occurred during the trans-medium process. The simulation of the water entry process of the trans-medium vehicle under different ventilation flows and deflection angles of the cavitator was carried out to investigate the flow field and cavity evolution laws during the trans-medium process. In addition, the fluid dynamics characteristics, as well as the kinematic characteristics of the vehicle during trans-medium process were analyzed. The simulation results show that the vehicle will present two different attitude change modes with the change of the ventilation flow during the water entry process: the increasing angular velocity leveling mode and the periodical pitching-type leveling mode. The water entry leveling process of the vehicle in different modes will show different motion characteristics. Moreover, an increase in the deflection angle of the cavitator and a decrease in the ventilation flow can improve the attitude change rate of the vehicle during the trans-medium water entry process.