Micro-detonation: can rapid reaction waves result from void-void interactions in shocked energetic crystals?

Mesoscale reactive calculations typically capture hotspots due to the collapse of micron-sized voids in HMX where the burn front velocities are ~100 m/s. However, recent continuum calculation cases have reported detonation-like behavior for multiple pores in proximity, where local pressures could rise to von Neumann spike (vN) values approaching 50 GPa and burn front velocities exceed 5 km/s. This phenomenon is akin to shock-to-detonation transition (SDT) but occurs at micron length scales, hence termed micro-detonation in this work. Macroscale SDT predictions relying on burn models agnostic of such mesoscale phenomena may yield unreliable metrics for run-to-detonation distances and go/no-go criteria. We ask what factors (void size, relative distance, orientation, etc.) might be responsible for triggering the burn-front to couple with the overpassing incident shockwave. The computations are performed using a sharp-interface framework that combines high-order schemes, Riemann-based interfacial treatments, an advanced MD-informed material model, and a Tarver 3-step reaction model for capturing the reactive flow dynamics. The study aims to probe the physics behind the rapid reaction waves approaching detonation velocity, shedding light on the influence of neighboring instances of collapsing voids as seen in clusters of pores/cracks versus uniformly distributed heterogeneity on hotspot ignition and growth.