Studying the Interaction of Shocks and Turbulence in a Variable-Density Experiment

Inertial confinement fusion (ICF) capsules are often driven by multiple shocks. As the first shock travels across the ablator-fuel interface, imperfections in the interface give rise to the Richtmyer-Meshkov instability. Additionally, as the capsule accelerates and collapses, the density disparity between the ablator and fuel also creates the Rayleigh-Taylor instability. While questions remain to the nature of this mixing region, i.e., is it turbulent or not, a second shock crossing the layer will drive the mixture turbulent. Any additional shocks will then be crossing a variable-density turbulent mixing layer. Some single fluids studies have previously shown that shocks amplify the turbulence, increasing the velocity fluctuations and decreasing the length scales, while others have observed opposing effects. DNS simulations of shocks interacting with variable-density turbulence indicate an increase in the turbulence is expected. We seek to experimentally study the effect of shocks on variable density turbulence using the Vertical Shock Tube at Los Alamos National Laboratory. We have captured simultaneous velocity and density fields for an Air-SF6 turbulent layer and initial results have found that the turbulent intensity increases while the Taylor microscale decreases, suggesting an increasing in the mixing. We will discuss the results to date, including a comparison on the effects on the vorticity, the turbulent kinetic energy and the mixedness across different Reynolds number flows.