Analyses of conditional moment closure for turbulent premixed flames

Direct numerical simulation data sets of turbulent hydrogen-air premixed flames with u'/S-l approximate to 30 are analysed with a view to model development. Conditional moment closure (CMC), an alternative to the flamelet approach for turbulent flames with high u'/S-l, is studied using the above DNS database. Variation of different terms in the CMC equation is studied. A priori tests of the conditional reaction rate closure are carried out. It seems that the first moment closure strategy, the conditional reaction rate as a function of conditional averages, is good. A simple model is proposed for differential diffusion of heat and mass from the CMC point of view and the predictions of the model are found to be very good. Behaviour of conditional streamwise velocity is studied. Three different models for the conditional velocity are tested a priori using the DNS data.