Effects of transverse shock waves on early evolution of multi-mode chevron interface

Abstract

Effects of transverse shock waves are important in the evolution of a multi-mode interface. However, the related experimental studies are scarce due to the difficulty in creating a well-defined interface. In the present work, we realized such an experimental study by using the soap film technique to form a multi-mode chevron air/SF6 interface. By changing the shock Mach number and the initial amplitude of the interface, the intensity of the transverse shock waves is varied. It is found that the impact of transverse shock waves together with the shock proximity effects flattens the bubble front and reduces the amplitude growth rate. For small initial amplitudes where the transverse shock waves are weak enough, the interface deforms little and the mode coupling is proven to be weak. For high initial amplitudes, the inverse cascade of modes causes the amplitude increase (decrease) of the first mode (high-order modes) at low Mach numbers. As the Mach number increases, the transverse shock waves and the shock proximity effects introduce external forces to the flow, resulting in the generation of additional high-order modes and the reduction in the first mode amplitude. Specifically, the augment of the second harmonic mode amplitude is crucial to flattening the bubble front.