Effect of compressibility on bubbly cavitating flows

Abstract

Cavitating bubbly flows can form in separated flows and shear layers leading to local regions high vapor void fraction, and these flows often exhibit periodic shedding of vaporous clouds. Historically, the presence of a liquid re-entrant flow, driven by the kinematics of liquid flow stagnation, has been identified as an important mechanism leading to cavity shedding. However, high local vapor void fractions can also result in a reduced mixture speed of sound and a possible supersonic flow. Our recent findings on different geometries indicate that propagating bubbly shocks in these flows are a primary mechanism of flow instability. In this study, we discuss the effect of compressibility on four geometries, mainly in the generation of propagating bubbly shocks that can influence the cavitation shedding dynamics. In order to elucidate the differences and similarities of the observed cavitation dynamics, and the influence of compressibility, we report observations from a backward facing step, backward facing wedge, NACA0015 hydrofoil, and a bluff body with a wedge cross section.