Dolphin-leap of the torpedo and the selection of the initial rotational angular velocity

Abstract

The process which the torpedo, with relying on its inertia, jumps out of water in a certain gesture and falls into water, is called dolphin-leap. According to the dolphin-leap, the torpedo is required to get into the water at its zero angle of attack, but this gesture cannot be controlled during the torpedo moving in air. In order to solve the problem, a solution to control the initial water-exit rotational angular velocity is developed according to the proposed dolphin-leap model. The variables like added mass, buoyancy, buoyant center, wetted area, wetted volume, etc. are dependent on water-exit gesture and process. The derivative term of each physical quantity is fully considered in the dolphin-leap model, and the relationship between torpedo's hydrodynamic drag coefficient and attack angle is analyzed, then the motion model is built and the torpedo's dolphin-leap law is obtained. The optimal search algorithm is used to obtain the initial rotational angular velocity which makes the torpedo dolphin-leap fall into the water at its zero angle of attack. Simulation results show the validity of the proposed model and the solution for controlling the initial rotational angular velocity.