Cavitation inception following shock wave passage

Cavitation bubble nucleation following the passage of an extracorporeal shock wave lithotripter pulse is investigated experimentally and numerically. In the experiments two configurations are considered: Free passage of the shock wave, and reflection of the shock wave from a rigid reflector. The nucleation and the early growth phase of the bubbles including radial and translatory motion is compared with a commonly used model for bubble dynamics, the Gilmore model, which is coupled to a one-dimensional model for translatory motion. Reasonable agreement is found for the predicted translatory motion of the bubble center; however, considerable disagreement between a simple cavitation inception theory and the experiment exists: Cavitation bubbles expand later than predicted pointing to a more complex inception scenario than a single stabilized gas pocket. A hypothesis is proposed to explain the delayed growth of the bubbles. Additional findings are the formation of bands with diminished bubble activity, which very much resemble the structure found by Sokolov et al. (2001). High-speed photographs suggest that bubble¿bubble interaction plays an important role in the formation of structured bands.