Laminar flamelet expressions for pressure fluctuation terms in second moment models of premixed turbulent combustion

New reading flow models are proposed and tested for all pressure fluctuatio n covariances that are known to play a crucial role in the second moment cl osure of the averaged equations of turbulent flows. The models, which are a pplicable to the thin laminar flamelet regime of premixed turbulent combust ion, are based on a partitioning of each covariance into contributions from reactants, products, and thin flamelets. Intermittency between the conditi onal mean pressure gradients in reactants and products is found to play an important role in the resulting expressions. The proposed models are extens ively tested using two-dimensional direct numerical simulation (DNS) of pre mixed combustion in decaying turbulence. The compressible flow code include s effects of finite heat release controlled by an assumed global reaction r ate mechanism. Good agreement is found between the model expressions and pr essure fluctuation covariances evaluated from DNS. (C) 2000 by The Combusti on Institute.