Oblique Detonation Waves Exhibit Micro-jetting*

A highly-resolved 2-D Direct Numerical Simulation (DNS) of a wedge-induced Oblique Detonation Wave (ODW) using a detailed 9-species 21-reaction chemical kinetic mechanism for a H2-air mixture is conducted. Adaptive Mesh Refinement (AMR) is leveraged to obtain a sub-micron resolution of ∆x = 0.78μm at the finest level (which spans the ODW front and its transverse waves). The simulation is performed for an extended domain to unravel the different instability patterns observed on the ODW front. We capture, for the first time, the onset of microscopic hypersonic jets far downstream of the wedge-tip that lead to cellular instabilities resembling those of a Normal Detonation Wave (NDW). A "psuedo-cellular" zone devoid of the classical NDW triple-points and the micro-jets is also spotted upstream of the cellular zone. A detailed investigation into the shock structure downstream reveals that a pair of transverse waves are critical to the jetting phenomenon. The absence of one of the pair of transverse waves in the upstream region results in the observed pseudo-cellular "half-cell-like" instabilities. Detailed temporal analyses on the divergence of the velocity field is conducted to elucidate further on the origin of these transverse waves in an ODW.