Influence and mechanism analysis of spatial heterogeneity on the propagation characteristics of near-limit detonation

The present work numerically investigates the effects of periodic sinusoidal and more realistic random spatial heterogeneities on near-limit detonation propagation in a thin explosive slab confined by inert layers and analyzes the mechanisms of these effects. Random heterogeneity is modeled by superimposing sinusoidal ripples with random center coordinates. Results demonstrate that sinusoidal and random heterogeneities with appropriate sizes, particularly 5-50 times the half-reaction zone length, produce clear regular and irregular cellular-like complex shock structures, respectively, and enhance propagation velocity, thus narrowing the critical thickness corresponding to the thinnest reactive layer for self-sustained detonation. Larger amplitudes or random distributions, representing higher degrees of heterogeneity, further extend propagation limits. In contrast, heterogeneities with wavelengths smaller than the reaction zone are rapidly averaged out, and the detonation characteristics converge to those of the homogeneous case. When the size of individual perturbations is comparable to the charge thickness, a velocity deficit occurs. The mechanisms of the impact of appropriate-sized and large-sized heterogeneities on detonation propagation are explained from the perspectives of energy release and loss. Appropriate-sized heterogeneities cause localized energy release inhomogeneity, inducing unstable transverse waves and triple-point structures that accelerate reaction rates, while elevated inert layer impedance mitigates lateral losses. The influence mechanism of large-scale heterogeneities lies in the alteration of sonic surface positions. As the detonation wave passes through the high-density zone, a significant portion of the heat is released outside the sonic surface, and more explosives at the edge of the high-density zone are driven into the inert layer.