Morphology of Micro-Jets in Fully Three-Dimensional vs. Narrow-Channel Detonations

Micro-jetting plays a central role in governing detonation cell growth, ignition dynamics, and global wave behavior. Although two-dimensional and narrow-channel configurations are widely used to study these mechanisms, it remains unclear how faithfully such reduced configurations capture the true three-dimensional micro-jetting dynamics. To address this, we perform high-resolution simulations of hydrogen detonations in fully three-dimensional and narrow-channel domains. Free-slip walls are first applied in the narrow-channel case to remove wall-loss effects and isolate the influence of confinement alone. A single detonation cell is tracked in each configuration, and the evolution of micro-jets and their associated vortex structures is examined. The fully three-dimensional detonation exhibits fundamentally different jetting morphology, where the collision of four transverse triple lines produces a closed vortex ring and a characteristic mushroom-shaped jet, in contrast to the counter-rotating vortex pair generated by two triple-line collisions in the narrow-channel case. The consequences of these morphological differences for global detonation properties are quantified. To further assess the role of wall-losses, an additional narrow-channel simulation with no-slip boundaries is performed, revealing weaker shock front and transverse waves, reduced jet strengths, and lower mean pressure and temperature. Together, the results delineate how dimensionality and wall-losses jointly shape micro-jetting and detonation properties.