Cavitation Inception During the Interaction of a Pair of Vortices*

Cavitation inception in shear flows often occurs in secondary stream-wise vortices (braids) stretched by spanwise vortices. Stretching of the weaker secondary stream-wise vortices can lead to a rapid drop in core pressure below the vapor pressure, and thus inception of captured cavitation nuclei in the core.  To better understand this inception mechanism, we will examine the interaction of two parallel vortices of unequal strength created by two hydrofoils mounted in a re-circulating water channel following the study of Chang et al. (2012). We will use tomographic Particle Image Velocimetry to examine the stretching of the secondary vortex and to analyze the flow field to estimate the transient core pressure. Experimental observations of the twin vortex instability will be compared to analytical predictions using methods suggested by Crouch (1997).