Turbulence generation by shock interaction with a highly nonuniform medium

An initially planar shock wave propagating into a medium of nonuniform density will be perturbed, leading to the generation of postshock velocity perturbations. Using numerical simulations we study this phenomenon in the case of highly nonuniform density (order-unity normalized variance, sigma(p)/(rho) over bar similar to 1) and strong shocks (shock Mach numbers (M-s) over bar greater than or similar to 10). This leads to a highly disrupted shock and a turbulent postshock flow. We simulate this interaction for a range of shock drives and initial density configurations meant to mimic those which might be presently achieved in experiments. Theoretical considerations lead to scaling relations, which are found to reasonably predict the postshock turbulence properties. The turbulent velocity dispersion and turbulent Mach number are found to depend on the preshock density dispersion and shock speed in a manner consistent with the linear Richtymer-Meshkov instability prediction. We also show a dependence of the turbulence generation on the scale of density perturbations. The postshock pressure and density, which can be substantially reduced relative to the unperturbed case, are found to be reasonably predicted by a simplified analysis that treats the extended shock transition region as a single normal shock.

Automated summary

This study investigates the phenomenon of an initially planar shock wave propagating into a medium of nonuniform density through numerical simulations. The results show that highly nonuniform density and strong shocks result in perturbations and turbulent flow. The analysis reveals that the properties of postshock turbulence are influenced by the initial density configuration and shock drive.