The Study of Propeller Cavitation Noise Using Cross-Correlation Methods

Abstract

This paper presents a technique for the study of the mechanisms responsible for the generation of noise from cavitating propellers. The experimental method, which involves the cross-correlation of the pressure gradient in the near-field of the propeller with the far-field sound, allows the determination of the spatial distribution of acoustic source strength on and near the cavitating propeller. The paper describes the mathematical basis for the cross-correlation technique, and then presents some of the results from experiments with propellers specifically designed to produce vortex and bubble forms of cavitation. Cross-correlations performed at a number of points along a track parallel to the axis of the propeller indicate that most of the noise from propellers producing vortex cavitation originates from the region of vortex collapse. A bubble cavitation propeller showed a region of relatively constant source strength distribution from the propeller disk region downstream to the point of vortex collapse.