A solution-adaptive method for efficient compressible multifluid simulations, with application to the Richtmyer-Meshkov instability

The evolution of high-speed initially laminar multicomponent flows into a turbulent multi-material mixing entity, e.g., in the Richtmyer-Meshkov instability, poses significant challenges for high-fidelity numerical simulations. Although high-order shock- and interface-capturing schemes represent such flows well at early times, the excessive numerical dissipation thereby introduced and the resulting computational cost prevent the resolution of small-scale features. Furthermore, unless special care is taken, shock-capturing schemes generate spurious pressure oscillations at material interfaces where the specific heats ratio varies. To remedy these problems, a solution-adaptive high-order central/shock-capturing finite difference scheme is presented for efficient computations of compressible multi-material flows, including turbulence. A new discontinuity sensor discriminates between smooth and discontinuous regions. The appropriate split form of (energy preserving) central schemes is derived for flows of smoothly varying specific heats ratio, such that spurious pressure oscillations are prevented. High-order accurate weighted essentially non-oscillatory (WENO) schemes are applied only at discontinuities; the standard approach is followed for shocks and contacts, but material discontinuities are treated by interpolating the primitive variables. The hybrid nature of the method allows for efficient and accurate computations of shocks and broadband motions, and is shown to prevent pressure oscillations for varying specific heats ratios. The method is assessed through one-dimensional problems with shocks, sharp interfaces and smooth distributions of specific heats ratio, and the two-dimensional single-mode inviscid and viscous Richtmyer-Meshkov instability with re-shock.