Numerical Simulations of Detonation Re-initiation Behind an Obstacle

Abstract

This numerical study explored the mechanisms responsible for the re-initiation of a detonation, which quenched while diffracting over a half-cylinder obstacle. Its purpose was to accurately predict when detonation re-initiations occur, determine roles of re-initiation mechanisms, and compare effects of chemical models. The model used reactive Euler equations with the one-step Arrhenius or two-step chain-branching chemical models, calibrated to post-shock conditions to reproduce the ignition delay. Simulations were validated using the stoichiometric methane-oxygen experiments of Bhattacharjee et al.. The model accurately predicted detonation re-initiation conditions found in experiments with good qualitative and quantitative agreement. While the one-step model was sufficient in predicting re-initiation, the two-step model reproduced finer details. Kelvin-Helmholtz and Richtmyer-Meshkov instabilities did not appear to influence detonation re-initiation of the Mach stem. Detonation re-initiation occurred due to adiabatic compression of the Mach stem, or transport of a flame along the wall jet. Transverse detonations were poorly reproduced.