Investigations of the Sound Generated by Supercavity Ventilation
An investigation is made of the sound generated by the impingement of a ventilating jet on the gas-water interface of a ventilated supercavity. A ventilated supercavity is a gaseous envelope generated around an underwater vehicle that allows for order of magnitude increases in vehicle speeds. However, the hydrodynamic noise generated by the supercavity can interfere with successful deployment of the vehicle. One of the principal mechanisms of noise generation is believed to be the impingement
... the cavity ventilating gas jets on the gas-water cavity wall. An understanding of the acoustic field generated by this interaction has been developed by analysis of a series of model problems which approximate the geometry and physical mechanisms involved in the jet-cavity interaction. The first problem is that of a spherical, gas-filled cavity in water whose surface is excited by a planar ring of axially projecting jets originating from the center of the sphere. The second involves a jet of infinitesimal cross-section impinging at normal incidence on the gas-water interface. The final problem makes use of a creeping mode diffraction theory to estimate the 'self-noise' produced by the impinging jets on the solid nose of the vehicle. These problems provided insight into the general characteristics of the field and its dependence on typical flow conditions. To apply these solutions to the problem of the supercavity, experimental studies were made in collaboration with the Applied Research Laboratory (ARL) at Penn State University. These included measurement of the unsteady force exerted by a jet on an interface, the results of which have been used to make theoretical predictions of the self-noise generated by a model-scale supercavity currently in use at ARL. The final results of this project will aid current and future naval research into supercavity noise and methods for its reduction.