Compressibility effect on shock-induced air/helium chevron interface evolution

Shock tube experiments of a periodic air-helium chevron interface impacted by a planar shock wave are conducted. Effects of the compressibility and the initial amplitude on the perturbation growth are highlighted. For small initial amplitudes, the shock Mach number has limited effects on the reliability of the linear model. For high initial amplitudes, however, the linear model is generally invalid because the high amplitude effect will reduce the linear growth rate. Under the high initial amplitude condition, the increase of the shock Mach number further aggravates the discrepancy of the experimental result with the theoretical prediction. By considering the high amplitude effect and the high Mach number effect, the linear growth rate of the interface with high initial amplitude impacted by a strong shock wave can be well predicted. The compressibility effect induced by the incident shock wave can be illustrated by the material compression and the geometric compression of the interface, and the latter is found to be dominant. In the nonlinear regime, some nonlinear models proposed for single-mode interfaces are verified to be valid only at very early stages.