Dynamics analysis of high-speed water entry of axisymmetric body using fluid-structure-acoustic coupling method

The high-speed water entry problem of a rotating body has instantaneous and strong nonlinear characteristics. In order to study the unsteady evolution of the multiphase flow field entering the water and the coupling effect of multiple media and analyze the influence of the noise of different structures, the fluid–structure-acoustic coupling method is used to analyze the numerical simulations of high-speed vertical water entry with different structures are carried out. In this article, we use different materials and structural forms of rigid cylinder, elastic cylinder and concave-head cylinder to analyze the unsteady evolution of the flow field during the water entering process, the dynamic response of the structure and the water flow noise. Through the comparison and analysis of different materials and structural forms, it can be found that the impact load of the rigid cylinder to the water has increased significantly and appeared earlier, the diameter of the cavity contour of the rigid cylinder is small, and the cavity and contraction of the tail of the concave-head cylinder faster. At the same time, the stress distribution of the elastic cylinder and the bottom of the concave-head cylinder is annular, and expands outward along the bottom center, and the stress transmission of the side surface of the concave-head cylinder is faster. Finally, the overall sound pressure level (OSPL) of the three different structures inflow noise at different distances in the four azimuths has basically the same change, and shows a ”saddle-shaped” trend. The research results in this paper can provide a certain reference for the study of multiphase flow field evolution, structural dynamic response characteristics and noise characteristics of high-speed entering water.