Phase transition dynamics during a single cavitation bubble growth inside a water droplet

Understanding of secondary phase transitions during non-spherical bubble growth and collapse remains limited in the current literature. Such transitions can be triggered by rarefaction waves resulting from reflected shock waves or rapid flow acceleration during bubble growth and rebound. In this study, a fully compressible three-phase flow solver with high-resolution interface capturing schemes and a phase change model is utilized to accurately capture the dynamics of secondary cavitation formation and collapse. The model is validated through simulations of a laser-induced cavitation bubble inside a millimetric water droplet. Results demonstrate the occurrence of secondary cavitation formation and collapse due to the rarefaction wave reflected from the droplet's surface, consistent with experimental observations. Additionally, simulations reveal that the phase transitions focus and lead to explosive cavitation events occurring at a similar distance from the bubble's center but on the opposite side of the droplet. Furthermore, the influence of droplet surface stand-off and curvature parameters on phase transition dynamics is also discussed. Notably, curved drop geometries give rise to more intricate rarefaction waves and phase transition dynamics.