Measurements of Pressure and Nuclei in a Pair of Interacting, Cavitating Vortices

Incipient cavitation in turbulent shear flows typically first occurs in the weaker stream-wise vortical structures rather than in the stronger span-wise vortices. The weaker (secondary) vortical structures are stretched by the stronger (primary) structures, leading to a transient drop in the core pressures of the weaker vortices. This work studies this phenomenon experimentally by examining the interaction of two initially parallel line vortices experiencing the Crow instability. The tip vortices of a pair of hydrofoils set in a recirculating cavitation channel are used to form this interaction. Inception in the vortices is interrogated with high speed video and acoustic measurements. Pressures and vortex properties are measured in the single phase flow of the vortex interaction using Shake-the-Box particle tracking velocimetry. The nuclei content of the water channel is measured with a Cavitation Susceptibility Meter (CSM). The inception rate observed with acoustic and high speed video measurements is then compared to that predicted by the measured pressure fields and nuclei distributions.

This work was supported by Office of Naval Research, under program managers Dr. Ki-Han Kim and Dr. Julie Young, MURI Grant Number N00014-17-1-2676.