Volumetric Velocimetry Study of Cavitation Inception in a Stretched Vortex

Cavitation inception in turbulent shear flows occurs in the weaker stream-wise vortical structures more readily than in the stronger span-wise vortices. Vortex stretching of the weaker (secondary) by the strong primary vortex leads to transient reduction in pressure in the cores of the weaker (secondary) vortical structures, causing inception. This work is an experimental study of this phenomenon of cavitation inception during the interaction of two line vortices experiencing the Crow instability. A pair of initially parallel tip vortices are produced with hydrofoils in a re-circulating water channel. Cavitation inception is studied with high speed video and acoustic measurements. Based on single phase flow velocity measurements with high speed Shake the Box and Tomographic PIV velocimetry measurements, pressures within the vortex cores are estimated. The nuclei distribution of the water channel is measured with a Cavitation Susceptibility Meter (CSM), and the observed inception rate is then compared to that predicted by the measured pressure fields and nuclei content.

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