REIGNITION OF DETONATIONS BY REFLECTED SHOCKS

Numerical simulations are used to study the diffraction, decay, and re ignition that occurs when a detonation propagates past an increase in cross-sectional area in a rectangular tube. The computations solve the time-dependent two-dimensional equations describing a reactive flow i n an argon-diluted stoichiometric hydrogen-oxygen mixture at atmospher ic pressure. Previous studies have shown that soon after transmission to a larger area, the reaction front decouples from the leading shock and forms a decaying blast wave (''bubble'') in the larger tube. Then, depending on the initial conditions, the detonation either continues to decay or is reignited as the bubble reflects off confining surfaces . For a strongly overdriven initiating detonation, reignition occurs t hrough an interaction between the bubble and the original contact surf ace. For a more weakly driven system, reignition can occur in two ways : either in the slip line and Mach stem of the Mach reflection formed when the bubble reflects off the bottom surface of the tube, or by mul tiple shock interactions that occur when the reflected bubble overtake s the initial detonation front. The computations show the evolution an d development of the cellular structure of the steady detonation front .