On Reduction of Cavitation Noise and Pressure Fluctuation Induced by a Cavitating Propeller due to Air Injection

Abstract

In this paper, extensive experiments are described on pressure fluctuations and cavitation noise induced by a cavitating propeller working behind a complete ship model. Model of a conventional propeller and a highly skewed propeller both of which have injection holes near the leading edge, were used to determine the effect of air injection on sheet cavitation noise and pressure fluctuation, and to demonstrate the flow field on an unsteady propeller blade. The experiments were conducted without air injection and with air injected at different air flow rates. The results show that the injection of air into the cavity reduces cavitation noise by about 20 dB maximum. Little effect on pressure fluctuation and cavitation extent was observed. As the air flow rate increased from 04 liter/min, cavitation noise was reduced, but above 4 liter/min there was no further reduction. In this measurement, sophisticated experimental techniques were used to obtain significant data on cavitation extent, pressure fluctuations and noise in a cavitation tunnel. These were the wake simulation technique using flow liners and artificial nuclei seeding.