Investigating Unsteady Flow Physics Within Shock-Bubble Interactions

Abstract In efforts to elucidate the unsteady physics within shock-bubble interactions (SBI), two rectangular SBI problems were simulated with varying Atwood numbers. The problems of interest are: (a) the unsteady interaction of a Mach 1.17 planar shock wave with a square sulfur hexafluoride (SF6) bubble surrounded by air, and (b) the unsteady interaction of a Mach 1.21 planar shock wave with a square helium bubble surrounded by nitrogen. The expectations are to simulate the morphologies of these SBI fields, as the shock wave propagates throughout the media, and as the bubble is transported and deformed. In addition, plans are to quantitatively observe and document the complicated thermodynamic processes, such as, shock refraction, shock reflection and shock diffraction as they develop, interact and propagate through the field. In the cases of the problems investigated herein, at the edges of the rectangular bubble geometry, vortexes are expected to be induced due to shock compression, the generation of vorticity and the acceleration of the media. Numerous experiments have confirmed that this type of problems contain specific fundamental fluid physics that does not lend themselves to simulations without severe numerical challenges. Simulation challenges of great significance to this analysis are the evolution of known fluid instabilities, such as, the Kelvin-Helmholtz instability (KHI) and the Richtmyer-Meshkov Instability (RMI). The unsteady nature of the flow morphology was studied using the Integro-Differential Scheme (IDS) simulation tool. The IDS captured all known flow characteristics and their interactions. The SBI morphology derived from the IDS simulations closely matches the results obtained from experimental findings and the limited available CFD simulations.