Numerical study of detonation propagation in a semi-confined nonuniform layer bound by an inert gas

This study investigates detonation propagation through a stoichiometric hydrogen-oxygen layer stratified above an inert gas, i.e., argon, with a diffuse interface at atmospheric pressure. A simple model capable of replicating the detonation inert gas diffuse layer interaction was developed that simulates previously conducted experiments. Detonation propagation is modeled by solving the two-dimensional reactive Euler equations for a calorically perfect gas with single-step Arrhenius chemistry. The acoustic impedance gradient associated with the argon diffusion into the hydrogen-oxygen results in a nonuniform initial density. Because of the perfect gas assumption, for a uniform initial pressure, as in the experiment, results in an initial temperature that is artificially nonuniform. The activation energy is adjusted for the imposed temperature nonuniformity in order to yield the correct ZND reaction zone length for the local argon dilution. Numerical soot foils are compared to experiments. Detonation propagation is possible due to the generation of triple points along the diffuse layer interface. These triple points, that generate new detonation cells, form from inflections in the reaction zones that develop because of the local increases in detonation strength.