DNS analysis of propagation speed and conditional statistics of turbulent premixed flame in a planar impinging jet

Abstract

DNS is performed for turbulent premixed flames stabilized in planar impinging jets. Test cases are defined to allow independent evaluation of the effects of turbulent intensity and mean strain rate. Conventional NSCBCs are extended to allow multidirectional flow and compatibility of different types of boundaries. The turbulent displacement speeds are well predicted by the asymptotic relationship in terms of turbulent diffusivity and 1/L-w at the leading edge. Higher speeds of stagnating flames are due to higher 1/L-w's of the stretched flame brushes than those of freely propagating ones. Gradient diffusion may occur with a negative slip velocity throughout the flame region for a high turbulent intensity and a high mean strain rate. Turbulent intensities are anisotropic with the axial component increasing by production in unburned gas, while there is not much production of turbulence in burned gas near the wall. (C) 2010 The Combustion Institute. Published by Elsevier Inc. All rights reserved.