Detonation Initiation upon Interaction of a Shock Wave with a Combustible Gas Bubble

In this paper, we perform a numerical simulation of the interaction of a shock wave in a gas with an ellipsoidal combustible gas bubble of increased density in a two-dimensional plane and with axisymmetric formulations based on the Euler equations. Three qualitatively different modes of detonation initiation were found: direct detonation initiation in the front part of the bubble at sufficiently high Mach numbers of the incident wave and detonation initiation as a result of wave refraction and focusing of secondary shock waves in the rear part of the bubble at lower Mach numbers. The detonation initiation mode is shown to depend significantly on both the shock wave intensity and the bubble shape. The elongation of the bubble leads to a decrease in the threshold Mach numbers: moderately in the axisymmetric case and significantly in the case of plane symmetry. The effect of focusing the shock wave allows achieving successful detonation initiation at a fundamentally lower intensity of the incident wave compared to direct initiation.