Investigation of the Behavior of Ventilated Supercavities

A study has been carried out to determine various aspects of the flow physics of a supercavitating vehicle at the Saint Anthony Falls Laboratory (SAFL). For the experimental work presented here, artificial supercavitation behind a sharp-edged disk was investigated for various model configurations. Results regarding supercavity shape, closure, and ventilation requirements versus Froude number are presented. Conducting experiments in water tunnels introduces blockage effects that are not present in nature. As a result, effects related to flow choking must also be considered. Two methods for computing ventilated cavitation number were compared, the first based on direct measurement of pressure and velocity, and the second technique based on measured cavity geometry and the use of previous numerical results. The results obtained are similar in character to previously reported data, but differ in measured numerical values. An attempt is made to correlate results from water tunnel experiments, where blockage has a significant effect, to an unbounded open flow. Supercavitation parameters, especially the minimum obtainable cavitation number are strongly affected by tunnel blockage.