Non-premixed turbulent jet mixing using LES with the FMDF model

Many practical combustion devices and uncontrolled fires involve high Reynolds number nonpremixed turbulent flames that feature non-equilibrium finite-rate chemistry effects, e.g., local flame extinction and reignition, where enhanced transport of mass and heat away from the flame due to rapid turbulent mixing exceeds the local burning rate. Probability density function methods have shown promise in predicting piloted nonpremixed CH₄-air flames over a range of Reynolds numbers and varying degrees of flame extinction and reignition. A study was carried out to quantify and characterize the kinetics of localized extinction and reignition in the Sandia flames D, E, and F, for which detailed velocity and scalar data exists. PDF methods in large eddy simulation to predict the filtered mass density function (FMDF) was used. A simple idealized mixing simulation was performed of a nonpremixed turbulent fuel jet in an air co-flow. Mixing statistics from the Monte Carlo-based FMDF solution of the chemical species scalar were compared to those from a more traditional Eulerian mixing simulation using gradient transport-based subgrid closure models. The FMDF solution will be performed with the Euclidian minimum spanning tree mixing model that uses the phenomenological connection between physical space and state space for mixing events. This is an abstract of a paper presented at the 30th International Symposium on Combustion (Chicago, IL 7/25-30/2004).