Sound generated by a jet-excited spherical cavity

An analysis is made of the sound generated by the impingement of a high-speed ventilating gas jet on the gas–water interface of a ventilated supercavity. A precise analytical problem is formulated and solved in which the supercavity is modelled by a spherical cavity of equal interior volume and the jet consists of a planar, radially symmetric flow from the centre of the sphere. The gas content of the sphere is assumed to be maintained at a constant mean level by steady exhaust into the water from the ‘rear end’ of the cavity. It is estimated that the damping of jet-induced oscillations by this outflow is negligible compared with conventional losses produced by acoustic radiation and by viscous and thermal dissipation. The sound radiated into the water is omnidirectional at low frequencies, but with increasing frequency it progressively exhibits the directional characteristics of an acoustic dipole with axis centred on the radial axis of the gas jet.