Development of flame surface density closure for turbulent premixed flames based on a priori analysis of direct numerical simulation data

Abstract

In turbulent premixed flames the modelling of mean or filtered reac tion rate translates to the closure of flame surface to volume ratio, which is commonly referred to as the Flame Surface Density(FSD). The FSD based reaction rate closure is well established in the context of Reynolds Averaged Navier-Stokes (RANS) simulations for unity Lewis numbers. However, models for FSD in context of Large Eddy Simulations (LES) are relatively rare. In this study three-dimensional Direct Numerical Simulations (DNS) of freely propagating statistically planar premixed flames encompassing a range of different turbulent Reynolds numbers and global Lewis numbers was used. The variation of turbulent Reynolds number has been brought about by modifying the Karlovitz and the Damkohler numbers independently of each other. The DNS data has been explicitly Reynolds averaged and LES filtered for a prior assessment of existing FSD models and for the purpose of proposing new models where necessary.