THE BMC GIEM MODEL FOR MICROMIXING IN NON/PREMIXED TURBULENT REACTINGFLOWS/

A novel beta mapping closure (BMC)/generalized IEM (GIEM) model is pro posed to close the micromixing term in the joint composition probabili ty density function (PDF) transport equation for nonpremixed, multisca lar turbulent reacting flows. Because the beta PDF gives an excellent description of binary inert scalar mixing, it is used to approximate t he mixture fraction PDF. The proposed model thus effectively extends p resumed PDF methods to handle finite-rate chemistry without introducin g ad hoc assumptions about the form of the joint composition PDF. The BMC/GIEM model can be solved efficiently using a particle-based Monte- Carlo code. The model is first compared with the amplitude mapping clo sure (AMC)/GIEM model and homogeneous reaction-diffusion data for scal ar mixing with a two-step reaction. Its application to inhomogeneous f lows is demonstrated by simulating a reacting scalar mixing layer with a one-step reaction using a Lagrangian composition PDF(LCPDF)code. Th e linear-mean-square-estimation (LMSE) model is also evaluated for com parison. The results from the BMC/GIEM model are in excellent agreemen t with experimental data, whereas the LMSE model gives errors in highe r-order statistics.