Investigation on nonspherical bubble dynamics in a compressible fluid fully confined by a solid boundary

This study investigates the dynamics of a nonspherical bubble confined within a spherical solid structure boundary. A bubble dynamics model accounting for fluid compressibility and solid elasticity is developed for the boundary condition of full confinement. Using this numerical model, the influence of the bubble's eccentric position, confinement size, and boundary material on the bubble's nonspherical pulsation is explored. Four bubble behavior patterns are identified: quasi-spherical oscillation, internal jet fragmentation, post-collapse jet impact, and pre-rebound jet impact. The characteristics and evolution mechanisms of these behaviors are analyzed based on flow field pressure. The wall effect and fluid accumulation phenomenon are identified as the primary factors responsible for generating local high pressure on the bubble surface, which triggers the different pulsation behaviors. Furthermore, we summarize the dependence of these behaviors on various governing parameters, and the jet dynamics at the moment of jet impact are quantitatively analyzed. Finally, the structural pressure characteristics and stress distribution induced by the bubble behaviors are studied. We find that changes in the bubble's eccentric position not only lead to variations in bubble behavior patterns but also result in significant differences in structural pressure evolution. In terms of structural stress distribution, in addition to the structure surfaces near the bubble being prone to high stress, surfaces far from the bubble are also subjected to local high stress caused by fluid accumulation, which poses potential risks to the structural strength in that region.