Analysis of high-speed water entry in semi-sealed cylindrical shells: Cavity formation and self-disturbance characteristics

Abstract

The high-speed water entry of a semi-sealed cylindrical shell is a complex unsteady process involving the multiphase flow. In order to study the influence of special structure of the semi-sealed cylindrical shell, the fluid-structure interaction method based on Star-CCM+ and ABAQUS is adopted. The results show that semi-sealed cylindrical shells with different structures all form nested cavities, among which the shell with a shorter length forms a nearly spherical cavity, while the shell with a smaller diameter forms a cavity that is close to a long strip shape. When the Mach number of the initial impact velocity is lower than 0.16, the top wall of the shell can be completely restored as the jet leaves the top wall. The von Mises stress at the top wall of the shell is higher than that at the side wall position. The deformation at the top of shells with larger diameter, shorter length, and smaller thickness is greater. The high-speed vertical water entry process of the semi-sealed cylindrical shell exhibits unique self disturbance characteristics, indicating that shells with thicker thickness and a longer length will exhibit obvious deflection after the self-jet phenomenon occurs.