Compressible turbulent mixing evolving from Richtmyer-Meshkov and Rayleigh-Taylor instabilities and Bell-Plesset effects has been investigated using high-resolution implicit large eddy simulations of fundamental spherical implosion problems. Broadband (BB) and narrowband (NB) initial perturbations consisting of multimode cosine perturbations are considered at a high Atwood number ($A_t=0.9$) corresponding to a density ratio of 20. This research examines the turbulent transport and budgets of turbulent kinetic energy, turbulent mass flux, and density self-correlation, and the balance of the terms in the transport equations is used to approximate the numerical discretization effect on the derived equations. Strong non-Boussinesq effects and asymmetries were observed in the distribution of the anisotropy terms and budgets within the mixing layer. The production and destruction terms dominate the late stages of the mixing process in all the equations compared to the other transport terms. The BB layer showed higher levels of density self-correlation compared to the NB case, which showed larger destruction levels relative to the state of the layer. Higher levels of turbulent mass flux and turbulent kinetic energy (e.g., larger potential to kinetic energy conversion rates) were observed in the BB case due to the longer-wavelength perturbations in the BB layer that dominate the growth at late times. The numerical discretization terms implicitly modeling the effect of the unresolved scales contribute to both diffusion and dissipation and the current study shows that their effect may be both examined indirectly through residuals and quantified directly through observed destruction.

• Received 28 October 2022
• Accepted 31 January 2024

DOI:https://doi.org/10.1103/PhysRevFluids.9.034501