Simulations of HED ensemble experiments of shock-driven turbulence in a transitional state*

Shock-driven turbulence may develop when shocks interact with perturbations present at material interfaces. Thus, shock-driven turbulence can drive mixing between the multiple layers inside inertial confinement fusion capsules and play an important role in performance, and often necessitates the use of mix models to simulate these systems. In this work, we evaluate the performance of LANL’s BHR mix model in a transitional state, in which the meaning of ensemble averaging that the model is based on for fully developed turbulence problems is not straightforward. We conduct three-dimensional ensemble simulations of recent Omega-EP experiments in which multiple instances of the same target (same single-mode nominal profile but different surface roughness) are repeated to provide one of the first HED ensemble data sets of coupled Richtmyer-Meshkov and Rayleigh-Taylor instability growth. Turbulence statistics such as the turbulent kinetic energy (TKE) and density-specific-volume covariance are computed and serve as validation quantities for the BHR model. A large suite of two-dimensional simulations with BHR is undertaken, providing estimates for initial values of BHR-relevant parameters such as the initial TKE and initial turbulent length scale, useful for the modeling of future experiments.

This work conducted under the auspices of the U.S. DOE by LANL under contract 89233218CNA000001