Predicting the higher-order harmonics of propeller-induced hull-pressure fluctuations by tip-vortex cavitation

Cavitating propellers generate pressure fluctuations on the hull of the ship and emit underwater sound. These pressure fluctuations are usually analysed in the frequency domain with the spectrum composed of tonals at harmonics of the blade passage frequency and a broadband part. The two are often analysed separately through the amplitudes of the tonals and through the power density or power spectrum of the broadband part. The present paper discusses an analytical formulation that shows how the two are related through the variability of the pressure signal between blade passages. The formulation is also used to predict the tonals from the broadband part of the spectrum for which an semi-empirical model for tip-vortex cavitation is available.