Numerical study on the dynamic characteristics of water entry of cavity body using two-phase SPH method

The air usually has a major influence on the water entry of a typical cavity body (cavity body is a hollow, cylindrical, semi-closed structure), which not only lowers the slamming load but also affects the dynamic characteristics of water entry. In this paper, a two-phase smoothed particle hydrodynamics (SPH) model for simulating the water entry of cavity body is presented. The SPH model combined with Riemann solver is improved to deal with the two-phase flows with the discontinuous quantities across the interface. One-sided Riemann problem is used to impose the fluid–structure interaction and a switch-function-based Riemann solver dissipation is formulated to improve the interfacial instability owing to the strong impact. The motion equations of rigid body are incorporated into two-phase SPH model to describe the motion of cavity body. The proposed model is validated by research on the test cases in the published literature. Finally, this work presents a study of water entry of cavity body by experiment and this two-phase SPH method. The dynamics phenomena in the coupling process between cavity body and two-phase flow are investigated. And the effects of air, mass, the sizes and incline angles of cavity body on the dynamic characteristics of cavity body and two-phase flows are shown. Graphic abstract: An improved two-phase SPH model was used to simulate the water entry of cavity body. The cavity body impacts the water surface and the cavity body is closed by the flooding water. It comes into being open air cavity and water jets. The jet walls protrude and the air cavity is closed. With the increase of the water entry depth, the complex hydrodynamic phenomena can be seen again. The sinking depth shows the law of fluctuation up and down with time.[Figure not available: see fulltext.]