Numerical study of thermal nonequilibrium effects on Richtmyer-Meshkov flow driven by a heavy forward-triangular bubble.

This paper investigates the thermal nonequilibrium effects on Richtmyer-Meshkov (RM) flow driven by a heavy forward-triangular bubble. Numerical laminar simulations are performed by utilizing the compressible dimensionless Navier-Fourier equations obtained from the Boltzmann-Curtiss transport equation of nonmonatomic gases that consider translational energy-rotational energy transfer. Three distinct gases, including monatomic argon, diatomic nitrogen, and polyatomic methane, envelop a forward-triangular bubble that is filled with sulfur hexafluoride. Simulations are performed with a shock Mach number of 1.2. The simulations demonstrate that the thermal nonequilibrium and flow characteristics of nonmonatomic gases cause significant changes in the flow fields, which lead to complicated wave patterns, bubble deformation, and vortex dynamics. Using contours and spatially integrated fields of vorticity generation, degree of nonequilibrium, enstrophy, dissipation rate, and kinetic energy, a thorough analysis of nonmonatomic gases is conducted. The nonmonatomic gases produce larger rolled-up vortex chains, longer outward jet forms, and enormous mixing zones with strong, large-scale expansion in contrast to monatomic gases. Furthermore, a quantitative analysis of the time variations of interface features reveals that nonmonatomic gases have enhanced interface features. Lastly, a quantitative investigation is conducted into the consequences of thermal nonequilibrium characteristics. Two patterns are seen in spatially integrated fields: a rising trend in response to an increase in the bulk viscosity ratio and a falling trend in response to an increase in the inverse power-law index.