Richtmyer–Meshkov instability at gas/viscoelastic interfaces

This work investigates the Richtmyer–Meshkov instability (RMI) at gas/viscoelastic interfaces with an initial single-mode perturbation both experimentally and theoretically. By systematically varying the compositions and concentrations of hydrogels, a series of viscoelastic materials with tuneable mechanical properties is created, spanning from highly viscous to predominantly elastic. Following shock impact, the interface exhibits two distinct types of perturbations: small-amplitude, short-wavelength perturbations inherited from initial single-mode condition, and large-amplitude, long-wavelength perturbations arising from viscous effects. For hydrogels with high loss factors, viscosity dominates the interface dynamics, leading to pronounced V-shaped deformation of the entire interface accompanied by a rapid decay of the initial single-mode perturbation. In contrast, for hydrogels with low loss factors, elasticity plays a prominent role, leading to sustained oscillations of the single-mode perturbation. By employing the Maxwell model to simultaneously incorporate both viscous and elastic effects, a comprehensive linear theory for RMI at gas/viscoelastic interfaces is developed, which shows good agreement with experimental results in the early stages. Although deviations arise at later times due to factors such as the shear-thickening feature of hydrogels and three-dimensional effects, the model well reproduces the oscillation behaviour of single-mode perturbations. In particular, it effectively captures the trend that increasing elasticity reduces both oscillation period and amplitude, providing key insights into the role of material properties in interface dynamics.