1Engineering Physics, University of Wisconsin 2WCI, Lawrence Livermore National Laboratory
A nominally two-dimensional interface, unstable to the Rayleigh-Taylor or Richtmyer-Meshkov instability (RMI), will become three-dimensional at high Reynolds numbers due to the growth of background noise and 3D effects like vortex stretching. This three-dimensionality changes macroscopic features, such as the perturbation growth rate and mixing, as it enhances turbulent dissipation. In this study a 2D perturbation with small- scale, 3D fluctuations is modeled and allowed to evolve through time (Fig. 1) using the hydrodynamics code Miranda. A Mach 1.95 shockwave accelerates a helium/SF6 interface, similar to the experiments of Motl et al. [1], to explore the regime where a 2D dominated flow will experience 3D turbulent effects. We report on the structure and growth of the post-shocked interface, as well as mixing measurements and energy spectra. These metrics are compared against 2D simulations to probe the influence of three-dimensionality on the evolution of the RMI.
Figure 1. Time-evolution of the mass fraction isovolume of SF6 between 0.05 and 0.95 concentration
[1] Motl et al., “Experimental Validation of a Richtmyer-Meshkov Scaling Law Over Large Density Ratio and Shock Strength Ranges” Phys. Fluids (2009)
