Flow Instability: Richtmyer-Meshkov and Pulsating Flows

Aperiodic features like pits, voids, and engineering features like capsule fill tubes represent a critical yet incompletely understood source of material mixing in shock-accelerated interfaces relevant to inertial confinement fusion. Unlike well-studied periodic surface roughness, these anisotropic and inhomogeneous features violate the assumptions in classical models of Richtmyer-Meshkov and Rayleigh-Taylor-driven turbulent mixing. Their three-dimensional nature and lack of periodicity demand new experimental approaches to capture the complex flow physics they generate.

To provide detailed measurements of the evolution of large-scale perturbations following shock acceleration, we have conducted experiments 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. We present complete ensemble measurements of simultaneous velocity and density fields at four post-shock stations, capturing the temporal evolution of the mixing process. These measurements reveal the development of turbulent structures and provide critical data for validating models that must account for the inherently three-dimensional and anisotropic nature of feature-driven mixing. Preliminary results from ongoing reshock experiments, where the evolved mixing layer encounters a reflected shock wave, will also be discussed, potentially offering new insights into the compounded effects of multiple shock interactions on feature-driven turbulence.

Funding acknowledgement

This work was supported by the U.S. Department of Energy through the Los Alamos National Laboratory. Los Alamos National Laboratory is operated by Triad National Security, LLC, for the National Nuclear Security Administration of U.S. Department of Energy (Contract No. 89233218CNA000001)