Computational study of the interactions of two bubbles along an interface undergoing the Richtmyer-Meshkov instability*

In addition to its prevalence in astrophysics, the shock-driven growth of~interfacial perturbations (the Richtmyer-Meshkov instability, or RMI) has~important practical consequences in applications of fusion research. Our~objective is to numerically investigate the generation of vortex dipoles~that escape the confines of the mixing region, as well as the~reacceleration of bubbles, by focusing on the interaction of two adjacent~bubbles of different sizes subjected to the RMI. Our hypothesis is that~the escape of a vortex dipole can be predicted from the initial conditions~based on the vorticity associated with the bubbles. Simulations are~performed using an in-house, high-order accurate Discontinuous-Galerkin~code. We demonstrate deviations from existing bubble merging models in the~non-linear regime caused by the interaction of adjacent pairs of spikes,~which had not previously been considered. We further develop a criterion~that predicts the regime that will emerge for a given interface.