Comparison of Observed and Calculated Shapes of Travelling Cavitation Bubbles

Abstract

Recent observations of the geometries of growing and collapsing bubbles in typical cavitating flows (van der Meulen and van Renesse 1989, Briancon-Marjollet and Franc 1990, Ceccio and Brennen 1991, Kuhn de Chizelle et al. 1992) have revealed the complexity of the "microfluidmechanics" associated with these flows. Clearly the interaction of individual bubbles with the nearby solid surface and its boundary layer produce features in the dynamics of growth and collapse which were not present in experiments on bubbles in a quiescent liquid. These include several mechanisms for bubble fission prior to collapse and the role played by the concentration of accumulated vorticity in producing a hybrid vortex/bubble during collapse. The current paper presents a methodology for the calculation of the interaction between an individual bubble and the irrotational flow exterior to the boundary layer on a body. Comparison is made between computed bubble geometries and those previously observed experimentally. The calculations also reveal the effect which the bubble has on the irrotational flow around the body and consequently permits some preliminary evaluation of the interactions between neighbouring bubbles.