Prediction of Propeller Cavitation Noise and Its Comparison with Full Scale Measurement

Abstract

Propeller cavitation noise predicted both from theoretical calculation and from model experiment and compared with full-scale measurements performed on two ships, a cargo liner and a training ship. The tonal noise presenting discrete frequencies consisting of propeller blade frequency and its harmonics - associated with volumetric fluctuation of total cavitation bubble volume - and the broadband noise - associated with random growth and collapse of individual cavitation bubbles - are caused by different mechanisms. For this reason they should be treated separately in the theoretical and experimental prediction procedures. In model experiment, the principle of acoustic -mechanical reciprocity is applied for estimating the tonal noise. For the broadband noise a semi-empirical formula is applied for estimation in low frequencies. Full-scale measurements on actual ships were conducted to acquire far-field noise and to eliminate extraneous noise reflected from sea surface. The comparison between predictions and full-scale measurements has shown good agreement enough to prove that the present methods of cavitation noise prediction are valid for practical purposes.