Water entry of a floating body into waves with air cavity effect

Abstract

Based on a fully nonlinear time-domain higher-order boundary element method (HOBEM), the present paper investigates a semi-circular floating body entering obliquely into Stokes wave with air entrapment. In this model, a fifth-order analytical solution is used to simulate the Stokes wave as incident boundary condition. A long and thin jet layer is simulated and assumed to separate from wetted body surface along its tangential direction, which avoids fluid particular leaving or invading body surface. When inner free surfaces on both sides of body collide with each other, a closured air cavity is formed based on the assumption of adiabatic. Dual local stretched coordinate systems are applied to resolve the impact with air cavity effect and downward motion of inner jet due to the local impacts between two water surface which is mainly dynamic effects. Some auxiliary functions are employed to obtain the pressure distribution induced by wave impact. The developed model is verified against the published numerical results for water entry with air cavity effect in the absence of waves. Then, numerical simulations are undertaken to investigate the mechanism of wave entry with air cavity formation through designed parameters, i.e. wave amplitude, wave length, initial wave phase, initial air pressure, prescribed floating body velocity. Numerical results indicate that the presence of wave delays the formation of air pocket and leads to more asymmetric shape of air pocket with the increase of wave nonlinearity when the body impacts the wave peak. After the occurrence of air pocket, the fluid pressure sharply increases.