Direct numerical simulation of turbulent reacting flow using a reduced hydrogenoxygen mechanism

Abstract

Results of direct numerical simulations of hydrogenoxygen combustion using a partial-equilibrium chemistry scheme in three-dimensional, constant density, decaying, isotropic turbulence are reported. The simulations qualitatively reproduced many features of experimental results, such as superequilibrium radical species mole fractions, with temperature and major species mole fractions closer to chemical equilibrium. Areas of high reaction rate occurred in the simulations in sheetlike zones where regions of high scalar dissipation intersected the stoichiometric surface, as would be expected for near-equilibrium or flamelet combustion. Simulation results were compared with predictions of the Conditional Moment Closure model. This model was found to give good results for all quantities of interest when the conditionally averaged scalar dissipation was used in the prediction. When the nonconditioned average dissipation was used, the predictions compared well with the simulations for most of the species and temperature, but not for the reaction rate. The comparison would be expected to improve for higher Reynolds number flows, however.