Computational & Experimental Study of Shallow Bubble Collapse Mechanism in Gas Cells at Various Pressure Conditions

Ejecta production and transport has been generally characterized by the Ricktmyer-Meshkov Instability (RMI). Under certain shock conditions, RMI falls short in predicting the large amount of ejecta observed in experiments. The mechanism responsible for this increase in production has been identified and referred to as Shallow Bubble Collapse (SBC) mechanism. Ejecta produced by SBC is characterized by large areal mass releases (~10X more than RMI), very high temperatures (more than twice that observed in RMI), and higher velocities (~20% to 40% faster than RMI). SBC has been investigated under vacuum conditions. The current study aims to understand the effects of gas on the sourcing, transport and evolution of SBC ejecta. We have performed computations using LLNL's hydrodynamic code, ARES, and fielded experiments on gas guns for tin and cerium samples in various gases at different pressures.