NATURAL AND VENTILATED CAVITATING FLOW OVER HIGH-SPEED UNDERWATER VEHICLE

Abstract

Cavitation occurs around the underwater vehicle when the vehicle moves fast. We conducted the numerical calculation of natural and ventilated cavitating flow. The mechanism of the free surface and bottom wall effects on the cavity profile and stability are studied. Then we present a new passive flow control method using small protrusions as cavitators. Compared with the case without the cavitator, the supercavitating hydrofoil controlled by the cavitator shows a significant difference in the lift, while the drag changes little. Such a passive flow control method can only be applied when the cavitation number is low. At moderate cavitation number, air ventilation is needed. The ventilated cavitating flow over an axisymmetric projectile is investigated at a wide range of natural cavitation numbers, which is much more stable than the natural cloud cavitating flow. The results show that air ventilation can prevent pressure fluctuations and reduce drag significantly.