Shock acceleration of a vortex-perturbed interface*

Periodic surface roughness has been extensively studied as a source of material mixing at interfaces subject to shock acceleration as found in inertial confinement fusion capsules. However, non-periodic defects like pits, voids, and engineering features like the capsule fill tube have been identified as a significant contributor to mixing. Because of their anisotropic, inhomogeneous, aperiodic nature, these features break many of the assumptions that underpin models of variable-density turbulent mixing driven by the Richtmyer-Meshkov and Rayleigh-Taylor instabilities.

Some recent experimental and computational work has explored the behavior of large-scale defects in laser- or radiation-driven settings, including the formation of vortex-ring-like ejecta. However, the limitations of radiographic imaging have not allowed small spatial scales to be resolved, nor the measurement of density and velocity fields required by turbulence modelling. To provide more detailed measurements of the evolution of large-scale perturbations following shock acceleration, experiments have been developed in the Vertical Shock Tube (VST) at LANL wherein a weak vortex ring is used to deform a planar interface between air and SF₆ before the arrival of a M = 1.3 shock wave. The shock-deposited baroclinic vorticity then acts as the dominant driver in the post-shock flow. Ensemble simultaneous measurements of velocity and density fields will be presented at several post-shock times.