Experimental and numerical studies on detonation failure and re-initiation behind a half-cylinder

Abstract

Mach reflection causes the re-initiation of decoupled detonation owing to changes in the boundary. A complementary series of experiments and numerical simulations, illustrating detonation failure and subsequent reinitiation processes, have been presented. Immediately across the half-cylinder, the decoupled detonation owing to the diffraction effect wave is reflected on the bottom wall to form a regular reflection, and then changes into the Mach reflection, which further determines the detonation reinitiation. Two different reinitiation modes after detonation wave diffraction were observed for the stable mixtures: the direct Mach reflection re-initiation mode and Mach reflection combined with the transverse detonation. However, for unstable detonations, a different reinitiation mode was obtained, whereby the development of intrinsic instabilities resonates with the reflection on the bottom wall, rendering the Mach reflection randomly occurring or even absent. The critical limit of detonation failure is characterized by the radius of the half-cylinder and the cell size. In addition, the transition length from regular to Mach reflection was measured to reveal the length-scale effect on the process. • Two re-initiation mechanisms are proposed for stable and unstable mixtures respectively. • The detonation failure limit is dominated by the radius and detonation cell size. • The transition from regular to Mach reflection shows the existence of length-scale effect.