Matching Conditional Moments in PDF modelling of non-premixed combustion

The rate of generation of fluctuations with respect to the scalar values conditioned on the mixture fraction, which significantly affects turbulent non-premixed combustion processes, is examined in the paper. Simulation of the rate in major mixing model is investigated and the derived equations can assist in selecting the model parameters so that level of conditional fluctuations is better reproduced by the models. A more general formulation of the Multiple Mapping Conditioning (MMC) model that distinguishes the reference and conditioning variables is suggested. This formulation can be viewed as methodology of enforcing certain desired conditional properties onto conventional mixing models. Examples of constructing consistent MMC models with dissipation and velocity conditioning as well as of combining MMC with Large Eddy Simulations (LES) are also provided in the paper.