Effects of initial condition spectral content on shock-driven turbulent mixing

Area of Science:

• Fluid Dynamics and Plasma Physics
• Computational Physics

Background:

• The Richtmyer-Meshkov instability drives material mixing and turbulence in systems like fusion and astrophysics.
• Previous studies explored shock-driven mixing using numerical and laboratory experiments.

Purpose of the Study:

• To investigate how varying initial interface perturbations affect shock-driven mixing.
• To understand the transition to turbulence in a shock tube with differing fluid densities.

Main Methods:

• Three-dimensional (3D) numerical simulations using the rage code with implicit large eddy simulation.
• A shock-tube configuration with a sulfur hexafluoride (SF6) gas band in air, subjected to Mach 1.26 shocks.
• Systematic variation of initial spectral modes at the fluid interface while keeping perturbation properties constant.

Main Results:

• Decreasing the density of initial spectral modes led to up to 25% less total mixing at later times.
• Observed transition to turbulence driven by the Richtmyer-Meshkov instability.
• Analyzed the effects of rarefaction waves and reflected secondary shocks on the mixing process.

Conclusions:

• The number of initial modes significantly influences the extent of shock-driven material mixing.
• Findings suggest that simplifying initial conditions in simulations can reduce computational costs and improve accuracy.
• Implications for modeling material interfaces in 3D and reduced dimensionality simulations across various scientific fields.