Numerical study of water entry of vehicle under near free surface caused by underwater explosion

Abstract

Water entry of a high-speed vehicle with a small angle can easily cause such phenomena as bouncing and unstable trajectory. Underwater explosion near the free surface can provide better wave conditions for vehicle, which may significantly reduce slamming loads and improve trajectory stability. In this paper, numerical models of underwater explosion near free surface and water entry of a high-speed vehicle are established based on Coupled Euler-Lagrange (CEL) method of ABAQUS software. The feasibility of water entry of vehicle with small angle in underwater explosion bubble is verified by CEL numerical method. First, in order to verify the effectively of CEL method for solving problems of water entry and underwater explosion, experiment on water entry of projectile is carried out, a numerical models of a small projectile entering water and free-field underwater explosion are established. The obtained numerical results are compared with those of experiments or empirical formulas. Then, a water entry model of a high-speed vehicle with a small angle under static water surface conditions is established; and its slamming loads and motion trajectory during entry process are analyzed. Finally, numerical model water entry of a vehicle in an underwater explosion bubble is developed. The obtained results for the trajectory and slamming load characteristics are compared with those under static water surface conditions. The results show that underwater explosion near free surface can provide a cavity before water entry can significantly reduce the overload of the vehicle and effectively improve its trajectory stability during entry process. This study provides an innovative approach to reducing loads of a high-speed vehicle with small angle, which has a significant value for solving cross-media entry problems in the field of ships and ocean engineering.