Acoustic source strength measurements of cavitation noise in a water tunnel

Abstract

An experimental investigation of the noise generated by cavitation in turbulent shear flow is reported. The cavitation is produced by the flow through a sharp-edged orifice plate mounted in the test section of a 15.25-cm-diam water tunnel. The unique features of this experiment include the direct measurement of acoustic source strength using a reciprocity technique and the development of semi-empirical scaling laws for the noise produced. The source strength measurement method is useful for water tunnel cavitation noise studies because it is nonintrusive; the noise is measured by a reciprocal transducer located outside of the test section, in air. The scaling laws for orifice plate cavitation noise are developed to include the effects of pressure drop across the plate, the mean velocity through the plate, the cavitation number, and the air content level of the water. These scaling formulas were verified by running a similar test in a 30.5-cm water tunnel and comparing the measured source strength spectra to those predicted from the smaller tunnel results. [Work supported by the Applied Research Laboratory.]