Numerical Simulation of Post-Detonation Mixing with Detailed Chemical Kinetics

Numerical simulations were performed to examine the post-detonation processes produced by the detonation of a 12 mm-diameter hemispherical PETN explosive charge in air. The simulations captured post-detonation reactions, including air dissociation and afterburning, using a finite rate detailed chemical reaction model. The BKW real-gas equation of state is used for the gas phase to allow for the mixing of reactive species. A programmed burn model that converts the solid to a reactive gas at the CJ composition is used to seamlessly couple the detonation propagation to the reaction processes in the fireball. The computed blast, shock structures, and chemical composition within the fireball agree with measurements. The effects of mixing are explored in both 2D axisymmetric and 3D Cartesian coordinates. The evolution of the flow at early times is shown to be highly gas dynamic and matches well between both dimensions. The flow fields are azimuthally averaged in order to compare the mean and RMS values as time progresses, and allow for a mixing layer analysis to compare the growth of mixing layers based on different species. Soot particles will be included and their effects on mixing will be explored.