Amplitude impact on single-mode Richtmyer–Meshkov flow in a stratified heavy fluid layer

This study presents a systematic numerical investigation of the amplitude-dependent evolution of the Richtmyer–Meshkov instability (RMI) in a shock-driven stratified heavy-fluid layer. A high-order modal discontinuous Galerkin method is employed to solve the two-dimensional compressible Euler equations for a binary gas mixture, enabling accurate resolution of shock–interface interactions and the ensuing nonlinear flow dynamics. Grid refinement studies and validation against benchmark experiments confirm numerical convergence and robustness. The analysis focuses on how variations in the initial perturbation amplitude influence baroclinic vorticity deposition, interface deformation, and the coupling between RMI and Kelvin–Helmholtz instabilities. Flow visualizations and integral diagnostics—including circulation, enstrophy, and kinetic energy—demonstrate that increasing amplitude significantly enhances baroclinic torque, accelerates the transition from linear to nonlinear regimes, and promotes early vortex roll-up and intensified interfacial mixing. The interplay between amplitude and key flow parameters, such as shock Mach number, layer thickness, and Atwood number, is quantified, revealing that stronger shocks, thinner layers, and higher density contrast further amplify vorticity generation and instability growth. The results highlight amplitude as a critical control parameter governing the onset, strength, and morphology of RMI-induced mixing.