Numerical investigation on cavity dynamics of water-entry bodies with different shape parameters

Abstract

The cavity that occurs when a body enters water has a huge effect on the underwater motion of the body. Based on the theory of incompressible potential flow, a model for the study of water-entry cavity dynamics is established. The numerical process is divided into two phases. In the first phase, no cavity forms and the fluid slides continuously upward along the body surface. When the fluid particles on the body surface separate from the body during the flow, a cavity forms and the calculation enters the second phase. Calculating the change in the flow field around the cavity and the pressure of the air flow in the cavity allows us to determine the morphological changes in the cavity. When the cavity contracts and collides with the surface of the body, the cavity is cut into two parts. To verify the accuracy of the proposed model, the simulation results are compared with experimental results from a set of spheres entering the water. The model is used to simulate the water entry of bodies with different nose shapes and length-to-diameter ratios. The simulation results show that the cavity breaks into an annular shoulder cavity and tail cavity when the cavity collides with the body.