Calculating mix model parameters from ensemble turbulence experiments in the HED regime

Hydrodynamic instabilities are ubiquitous on interfaces that interact with shocks. These instabilities are often seeded by surface roughness that is too computationally expensive to resolve directly. Furthermore, the instability growth is often initially laminar, so that the best way to initialize sub-grid turbulence models (such as LANL's BHR) isn't readily apparent. Recent campaigns in the HED regime have used spanwise spatial lineout averaging when calculating turbulence quantities such as "b", the density-specific volume covariance. However, during the transition to turbulence the type of averaging used may be an important consideration when comparing experiments to turbulence models. Here, we will present the analysis of Omega-EP experiments in which a nominally identical single mode perturbation (up to surface roughness), heavy-to-light, RM with delayed onset RT experiment was repeated multiple times to generate an ensemble dataset. Experimental radiographs are converted to density maps, which are then registered and finally ensemble averaged in order to calculate 2D maps of density-specific volume covariance.