Shock-Induced Cavitation Inside Droplets*

Droplet aero-breakup is a complex phenomenon that yields a rich set of interface and hydrodynamic instabilities and potentially cavitation, especially when breakup is initiated by shock waves. Depending on the incident-shock intensity, internally reflected expansion waves form regions of metastable liquid that cavitate and couple to the droplet dynamics. Previous studies investigated the effects of the vapor cavity size and position on the droplet overall morphology and movement as well as the evolution of wave structures in the liquid region. An investigation on early-stage cavitation induced by shock waves is nonetheless missing. We present results of the interaction between a shock wave and a water droplet, focusing on early-stage cavitation. Simulations are carried out on MFC, a multi-component, multi-phase, bubbly compressible flows open-source tool. The homogeneous part of the 6-equation mixture model is solved by a flux-splitting approach and an explicit TVD RK time-marching scheme. HLLC- approximate Riemann solvers are used with proper correction for the quasi-conservative form of the equations and a high-order WENO scheme reconstructs the primitive variables. The nonhomogeneous part is solved by enforcing infinitely fast mechanical, thermal, and chemical relaxation procedures.