Numerical Simulation Study on Water-exit Motion of Unpowered Ascent Underwater Vehicles

The process of water-exit is the crucial part for the study of the stability of underwater vehicles. This study constructed a fluid-solid model of the underwater vehicle to comparatively study the ascent stability of the two ascent modes, which include the buoyancy drive up and specified speed drive up, and tried to predict the water-exist time. The model was applied for simulating the water-exit process of the two ascent modes through computational fluid dynamics (CFD) technology, and analyzing the effects of the different ocean current speeds and the mass of the underwater vehicle on the buoyancy stability and buoyancy speed. The numerical simulation results showed that the vertical displacement and the velocity of the two ascent modes for the water-exit motion were basically the same, but in terms of the yaw angle, the upward motions under the two ascent modes exhibited different behaviors, with the yaw angle of the buoyancy-driven upward motion being significantly larger than that of the upward motion at a given speed as the ocean current speed increased. Therefore, the numerical simulation method based on buoyancy-driven upward motion, rather than that based on given a speed, should be used for studying the yaw angle of the upward motion of a submerged vehicle.