Shock-driven discrete vortex evolution on a high-Atwood number oblique interface*

The shock acceleration of interfaces drives hydrodynamic instability growth, which in turn drives mixing across interfaces. This is an important yield degradation mechanism in inertial confinement fusion (ICF) implosions, where mixing across interfaces leads to the injection of high-Z material into the hot spot, quenching ignition. When shocks are oblique (i.e. the shock front is non-normal to the interface), a shear flow is driven across the post-shock interface, altering the subsequent instability growth. For some combinations of tilt, perturbation amplitude, and perturbation wavelength, the resulting instability growth exhibits mixed characteristics of the Richtmyer-Meshkov (RM) and Kelvin-Helmholtz (KH) instabilities. The growth is impulsive early in time, like RM, but exhibits the morphology and late-time behavior of KH. I will present new theory, simulations, and data showing that this complex instability growth can be understood as a consequence of the vorticity distribution created by the oblique shock-interface interaction. This work opens the door to future experiments in the HED regime where control over initial interface structure can be used to create arbitrary vorticity distributions on interfaces. Such a schema can used to create vortices with independently varying spatial scale, strength, and sign, which will enable a new generation of experiments studying the vortex-merger dynamics which dominate late-time behavior of mixing layers.