Interaction of a collapsing bubble with a gas pocket entrapped in solid

Cavitation bubbles collapsing near boundaries induce high-speed liquid jets due to the asymmetric pressure distribution around the bubbles. The behaviors of the collapsing bubble and liquid jet remarkably differ by the characteristics of the adjacent boundary. Recent studies have revealed that the small gas pockets entrapped on the solid boundary can mitigate the jet momentum and the surface erosion. In this study, we numerically investigate the cavitation bubble collapse near an entrapped gas by varying parameters such as gas compressibility and the volume of the air pocket. In most cases, the liquid jet is directed away from the boundary regardless of the thickness or volume of the gas pocket, indicating notable alleviation of the hydrodynamic loading on the solid surface. Furthermore, the effects of gas compressibility, the distance from the gas pocket to the bubble, and the configuration of the pocket on the bubble-gas pocket interaction are investigated.