Investigation of the Behavior of Ventilated Supercavities

Abstract

A study was carried out to investigate various aspects of an axisymmetric, artificially supercavitating vehicle. One of the main focuses of the study was to investigate the effects of blockage introduced when conducting experiments in a water tunnel. Blockage influenced all of the experiments investigated. The effect of blockage was to set a lower limit on the cavitation number attainable. Experimental results were compared to numerical results from previous researchers. Froude number effects on cavitation number and supercavity dimensions were investigated. An advantage of this study over previous supercavitation experiments conducted at Saint Anthony Falls Laboratory is the ability to directly measure the pressure inside the supercavity. This knowledge is important for an underwater vehicle that requires drag reduction, by means of an artificial supercavity, to accelerate to speeds where natural supercavitation is possible. Next, the effects of model configuration are investigated in two ways. The first is the effect of the size of disc cavitator, and the second is the influence of the presence of a body inside the supercavity. For a supercavity, the method of closure and air entrainment is an important design consideration. For this study, a detailed examination of the closure method for various model configurations was explored. Finally, an effort was made to correlate water tunnel experiments with unbounded flow. This was done by computing an equivalent unbounded flow cavitation number from values obtained in a water tunnel.