On the pressure dependence of ignition and mixing in two-dimensional reactive shock-bubble interaction

We analyse results of numerical simulations of reactive shock-bubble interaction with detailed chemistry. The interaction of the Richtmyer-Meshkov instability and shock-induced ignition of a stoichiometric H₂-O₂ gas mixture is investigated. Different types of ignition (deflagration and detonation) are observed at the same shock Mach number of Ma=2.30 upon varying initial pressure. Due to the convex shape of the bubble, shock focusing leads to a spot with high pressure and temperature. Initial pressures between p₀=0.25-0.75 atm exhibit low pressure reactions, dominated by H, O, OH production and high pressure chemistry driven by HO₂ and H₂O₂. Deflagration is observed for the lowest initial pressure. Increasing pressure results in smaller induction times and ignition, followed by a detonation wave. The spatial and temporal evolution of the gas bubble is highly affected by the type of ignition. The Richtmyer-Meshkov instability and the subsequent Kelvin-Helmholtz instabilities develop with a high reaction sensitivity. Mixing is significantly reduced by both reaction types. The strongest effect is observed for detonation.