Counter-Gradient Scalar Transport in Large Eddy Simulation of Turbulent Premixed Flames

Counter-gradient transport is examined in a priori large eddy simulations of turbulent premixed combustion using direct numerical simulations (DNS) of 3D planar flames. It is found that the size of the LES filter, and consequent resolution of the flame, have an important effect on the scalar flux and that this can be considered explicitly by decomposing the flux into flame interior and non-reacting components. The LES form of a scalar flux transport equation was written and models developed for the two main counter-gradient terms, the pressure gradient and velocity-reaction rate correlation.