Turbulence-Combustion Interactions in a Reacting Shear Layer

Abstract

Turbulence-combustion interactions are analyzed using results of a numerical simulation of a reacting shear layer. Premixed combustion at finite activation energy, moderate chemical kinetic rates and finite diffusivities is considered. The transport element method, a numerical scheme based on the accurate discretization of the vortiCity and the scalar gradient fields into Lagrangian finite elements, is used to perform the numerical simulation. Processes that lead to burning enhancement, flame deceleration or possible extinction are analyzed. We find that the rollup of the shear layer accelerates burning by stretching the reaction surface. However, by comparing the local burning velocities within the shear layer to that of a laminar flame, we find that stretch, which accompanies the rollup, decelerates the rate of burning per unit area. This is due to the local cooling effects associated with the enhanced heat flux out and mass flux into the reaction zone. Both phenomena are strong functions of the turbulence field and the Damkohler number.