Numerical study of converging shock wave interaction with offset gas bubble containing different gases - Ne, Ar or CO₂

This study presents a numerical investigation of the interaction between a converging shock wave and an offset cylindrical gas bubble containing Ne, Ar, or CO₂. Based on the good agreement with experimental findings shown in our previous study, we explored how these gases influence shock wave patterns when a converging shock wave propagating at a Mach number of 1.18 impacts a 50 mm diameter cylindrical bubble. The results reveal complex shock wave dynamics that differ from those observed when planar shocks impact on a cylindrical gas bubble or when a converging shock wave impacts a cylindrical gas bubble located at the center of its focus. Notably, in the case of a Ne-filled bubble, the shock wave focus is outside of the initial bubble location. Each gas produced distinct shock wave behaviors: the Ne bubble exhibited lens-like shock patterns, while in the Ar bubble's case the transmitted and converging shock waves were circular. A second shock wave focusing of the transmitted shock wave was observed inside the Ar bubble, similar to the case of the CO₂ bubble, which experienced earlier focusing than in the SF₆ case (previously studied) but later than Ar. The position of the transmitted shock wave's focus within the bubble varies with gas density, showing that heavier gases result in a focal point located further inside the bubble.