Some ways of hydrodynamic fin application for underwater supercavitating vehicles

The paper deals with considering the two non-traditional ways of application of hydrodynamic fins for a high-speed underwater supercavitating vehicles. The techniques for active roll stabilization and course control of the moving supercavitating vehicle are developed that use the regulation of the roll angle by means of both the special roll fin, and the automatic error-closing control system. The examples of a computer simulation of the course of maneuvering of the supercavitating vehicle controlled with the vertical hydrodynamic fins having zero roll angle stabilization are given along with the cases of the roll angle regulation. A method for determining the equilibrium motion parameters (balancing) of the supercavitating vehicle is developed for the case when a pair of identical horizontal cavity-piercing fins is used for complete or partial compensation of the vehicle's weight. The examples of a computer simulation of the motion of the supercavitating vehicle with horizontal fins in both the planing avoidance mode, and the combined mode are presented. It is shown that the steady-state longitudinal motion of the balanced supercavitating vehicle in the planing avoidance mode is stable "in the small", in contrast to its motion with planing in the cavity. It is found that, the horizontal fins in the combined motion mode can play a damping role suppressing the supercavitating vehicle motion instability "in the small", however, after a long time interval, the motion loses the global stability. The computer simulation suggests that the activation of the automatic depth stabilization makes the supercavitating vehicle motion stable in general in all the examined cases. Also it is revealed that course maneuverability of the supercavitating vehicle controlled with the vertical fins is maximal when starting the balancing in planing avoidance mode, but it deteriorates dramatically when starting the balancing in the combined mode.