Cavitation Bubble Collapse and Wall Shear Stress Generated in a Narrow Gap

Cavitation bubble dynamics in narrow gaps confined by rigid boundaries greatly differs from a liquid half-space. There exists a regime, where the bubble is created on one side of the gap and collapses on the opposite side. Additionally, the jet velocities may be considerably larger. The oscillating bubble and the impacting jets form complex boundary layer flows with greatly increased wall shear stress. The observations have implications for cleaning applications in narrow spaces. The experimental results show that the shear flow generated is active much longer after the collapse of the bubble. The results show approximately a 3-fold increase of the shear stress as compared to a liquid half space. We also present a space-time graph from numerical simulations. Additionally, the fluid dynamics is studied with the motion of particles attached to a substrate and the effect of shear on adherent biological cells.