The Richtmyer-Meshkov instability of a “V” shaped air/helium interface subjected to a weak shock

Abstract

The Richtmyer-Meshkov instability of a “V” shaped air/helium gaseous interface subjected to a weak shock wave is experimentally studied. A soap film technique is adopted to create a “V” shaped interface with accurate initial conditions. Five kinds of air/helium “V” shaped interfaces with different vertex angles (60°, 90°, 120°, 140°, and 160°), i.e., different amplitude-wavelength ratios, are formed to highlight the effects of initial conditions, especially the initial amplitude, on the flow characteristics. The interface morphologies identified by the high-speed schlieren photography show that a spike is generated from the vertex after the shock impact, and grows constantly with time accompanied by the occurrence of the phase reversal. As the vertex angle increases, vortices generated on the interface become less noticeable, and the spike develops less pronouncedly. The linear growth rate of the interface mixing width of a heavy/light interface configuration after compression phase is estimated by a linear model and a revised linear model, and the latter is proven to be more effective for the interface with high initial amplitudes. It is found for the first time in a heavy/light interface configuration that the linear growth rate of interface width is a non-monotonous function of the initial perturbation amplitude-wavelength ratio. In the nonlinear stage, it is confirmed that the width growth rate of interface with high initial amplitudes can be well predicted by a model proposed by Dimonte and Ramaprabhu [“Simulations and model of the nonlinear Richtmyer-Meshkov instability,” Phys. Fluids 22, 014104 (2010)].