Two-dimensional simulations with detailed chemistry are performed for hydrogen-oxygen-argon mixtures in channels with square obstacles to investigate how obstacle configurations influence detonation attenuation and flame acceleration. The results indicate that at a fixed blockage ratio, increasing obstacle dispersion enhances detonation attenuation by fragmenting the detonation front into discontinuous segments. Two distinct reinitiation modes in postobstacle sections are identified: for concentrated obstacles, reinitiation is directly driven by diffracted wave collisions; for dispersed obstacles, secondary reaction zones form behind the leading shock and develop into localized detonations through wave interactions and viscous dissipation. Subsequently, the stable propagation characteristics of detonation waves after sufficient attenuation within an extended obstacle section are examined. As the blockage ratio increases, propagation transitions from quasidetonation to choking regimes. In the quasidetonation regime, detonation undergoes repeated failures and reinitiations. In the choking regime, the attenuated wave degenerates into a nondetonative but coupled shock–reaction-front complex. The critical blockage ratio (${\xi }_{\mathrm{C}}$) determining the propagation regimes is identified, and the results indicate that ${\xi }_{\mathrm{C}}$ decreases with increasing detonation cell width, indicating that detonations with smaller characteristic scales are more capable of sustaining propagation through obstacle sections. The ratio of obstacle gap to cell width (δ/λ) is employed as a scaling parameter to quantitatively characterize velocity deficits and determine critical conditions for regime transitions. Finally, flame acceleration simulations confirm that obstacles corresponding to quasidetonation and choking regimes lead to detonation formation and nondetonative propagation, respectively. This demonstrates that obstacles exert competing effects, namely, shock attenuation and flame acceleration, and their balance determines the eventual propagation regime.

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