Numerical simulations of an inertially collapsing gas bubble with spherical perturbations

The inertial collapse of gas bubbles releases energy that can impact its surroundings which can be beneficial (lithotripsy) or unfavorable (material erosion from hydraulic cavitation). Impurities, external disturbances (e.g. acoustic waves), and/ or heterogeneities in the surrounding material will perturb the bubble interface during its collapse. Our aim is to investigate the inertial collapse of a single gas bubble with varying initial axisymmetric perturbations along the liquid-gas material interface. We initiate these perturbations to determine the amplification or dampening effect during the re-entrant jet evolution. We use the open-source Multi-component Flow Code (MFC) which solves the compressible Navier-Stokes equations using a five-equation multiphase numerical model [Bryngelson et al. Comp. Phys. Comm. (2020)]. Inertia dominates the collapse such that surface tension and phase change can be neglected. A resolution study is used to determine the mesh which captures perturbations of up to the fourth spherical harmonic mode. Considering prior Rayleigh-Plesset-type studies, we then conduct a parametric study of different initial spherical harmonic perturbations of the second and third mode. Simulation results and mode amplitudes of an initially perturbed bubble collapse near a free surface and near wall will be presented.