The control of ventilated supercavity pulsation and noise

A technique to control ventilated supercavity pulsation and noise is explored analytically and verified experimentally. The technique, which has its roots in parametric oscillators, changes the stiffness and, therefore, resonance frequency of the ventilated supercavity gas/water system by modulating or adding a sinusoidal component to the ventilation rate. This results in the ventilated supercavity effectively being driven off-resonance as the frequency of the interface waves which force the supercavity gas/water system remain largely unchanged. A wide range of ventilation rate modulation frequencies cause the pulsating supercavity to transition into twin vortex closure, typically within 0.25 sec of modulation initiation. Accompanying the transition from pulsation to twin vortex closure is a reduction in the radiated noise, to the continuum at the pulsation frequency, often by 35 dB or more. Other modulation frequencies do not suppress pulsation, but are effective at changing the supercavity pulsation frequency.