Experiments studying the impact of the initial conditions on multimode HED hydrodynamic instability growth*

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 isn't readily apparent. Here, we present recent Omega-EP experiments designed to address the impact of initial conditions on mix by resolving multimode Richtmyer-Meshkov with delayed onset Rayleigh-Taylor growth at both linear and deeply non-linear times. Three initial conditions are compared. The wavelengths of the nine modes present and overall perturbation amplitude are kept constant across perturbations, whereas the weighting between long and short modes is varied across perturbations.