SCALAR DISSIPATION RATE TRANSPORT AND ITS MODELING FOR LARGE EDDY SIMULATIONS OF TURBULENT PREMIXED COMBUSTION

Statistical behavior of Favre-filtered scalar dissipation rate (SDR) transport has been analyzed using direct numerical simulations (DNS) data of freely propagating statistically planar turbulent premixed flames. The DNS data has been explicitly filtered using a Gaussian filter to obtain the unclosed terms of the Favre-filtered SDR transport equation, arising from turbulent transport (T-1), density variation due to heat release (T-2), strain rate contribution due to the alignment of scalar and velocity gradients (T-3), correlation between the gradients of reaction rate and reaction progress variable (T-4), molecular dissipation of SDR (-D-2), and diffusivity gradients f (D). It has been found that T-2, T-3, T-4, (-D-2), and f (D) are the leading order contributors to the SDR transport and the magnitude of T1 remains smaller than the magnitudes of T-2, T-3, T-4, (-D-2), and f (D) irrespective of the filter width. Models are proposed for these terms in the context of large eddy simulations (LES) and their performances have been assessed with respect to their corresponding values obtained from explicitly filtered DNS data. These newly proposed models are found to satisfactorily predict both the qualitative and quantitative behaviors of these unclosed terms for a range of different values of filter widths Delta, heat release parameter tau, and turbulent Reynolds number Ret.