Transient dynamics of shock-induced cavitation bubbles inside the spherical droplet

Laser-induced explosions inside droplets can generate cavitation. This study investigates the transient cavitation process induced by laser-induced shock waves in spherical droplets. Modeling a mixed fluid of water, vapor, and air using a barotropic equation of state. And all phases are compressible. Using an explicit density based solver, 3D (three-dimensional) simulations were conducted for two eccentricity conditions of ε=0.4 and ε=0.6. The results successfully captured the coupling effect between shock waves and two-phase interfaces, as well as the development law of cavitation bubble clouds inside spherical droplets. A prediction of wavefront evolution process was established using ray parameter equations, providing a path diagram for the development of shock/rarefaction waves. Experiments, 3D simulations, and ray parameter equations confirm each other, revealing the core physical mechanism behind the generation of cavitation bubble clouds: the spatial convergence of rarefaction waves within spherical droplets leads to cavitation.