A model for the mixing time scale of a turbulent reacting scalar

Abstract

Current micromixing models in transported PDF (probability density function equation) modeling of initially nonpremixed, turbulent reacting flows ignore the direct influence of chemistry on the dissipation rate of reacting scalar fluctuations. Following mapping closure, a model for the time scale of reactive scalar mixing in the flamelet regime is developed and comparisons made with direct numerical simulations of a turbulent reacting jet. The modeling results show a significant improvement over the generally used estimate of substituting the time scale of the reacting scalar by that of a conserved scalar in traditional transported PDF approaches. The model can readily be applied to many existing mixing submodels used in transported PDF modeling when the time scales of the reacting scalars appear explicitly in the formulation. The submodels allow the transported PDF approach to now encompass the fast as well as slow chemistry regimes.