Experimental and staged simulation investigation of sympathetic detonation behavior in unconfined explosive charges

Sympathetic detonation (SD)—the unintended ignition of an explosive (acceptor) caused by the detonation of a nearby charge (donor)—poses critical risks in explosive storage and deployment. This study integrates near-field experiments with staged high-fidelity numerical simulations to investigate SD behavior in unconfined tri-nitrotoluene charges in air. Experiments under two initiation configurations reveal that detonation direction and stand-off distance significantly affect SD occurrence, with measured transmission distances of 40 mm (axial) and 15 mm (lateral), and corresponding safety distances of 100 and 30 mm. A three-dimensional direct numerical simulation framework employing high-order weighted essentially non-oscillatory schemes and multi-stage solvers resolves the coupled shock-to-detonation processes. The ignition and growth model is used to describe chemical kinetics, allowing the simulation of ignition phenomena otherwise undetectable in experiments. Numerical results align well with experimental data and uncover key near-field behaviors, including partial detonations, backblast-induced overpressure spikes, and ignition without macroscopic detonation. These findings highlight the limitations of traditional flow-field-based SD criteria and emphasize the importance of micro-scale reaction modeling in defining accurate safety margins. This multiscale approach offers a robust methodology for evaluating SD hazards and optimizing safety design in explosive systems.