Numerical simulation for water entry and exit of rigid bodies based on the immersed boundary-lattice Boltzmann method

The investigation on water entry and exit of rigid bodies is of great significance to prevent the marine equipment from hydrodynamic impact in ocean engineering. It is challenging to simulate this kind of problems in the framework of immersed boundary method because the rigid bodies are not always immersed in the fluid domain. In this paper, we propose a new method for simulating water entry and exit problems, by means of coupling the immersed boundary-lattice Boltzmann method with the single-phase free surface model. The key treatment in present method is the artificially filling interior algorithm, which is firstly developed in this paper to keep complete implementation of the immersed boundary condition. The accuracy, flexibility and effectiveness of the present method are verified through the water entry of a circular cylinder, the water entry of a wedge, and the water exit of a circular cylinder. The present numerical results are in good agreement with reference solutions. Additionally, for the water entry of a bow-flare section with various roll angles, severe numerical oscillations of impact forces appear in the solutions of traditional bounce-back lattice Boltzmann method, while the present method can accurately predict the impact forces with few oscillations. These numerical results well demonstrate that the present method is an effective tool for simulating the water entry and exit of rigid body problems.