Vectorial structure of the near-wall premixed flame

The turbulent premixed flame-wall interaction (FWI) has been numerically analyzed in a head-on quenching configuration at statistically stationary state under different boundary conditions. When the wall temperature is not high enough, the near wall flame isosurfaces become broken because of local flame extinction within the quenching and influence zones of FWI. According to the relative orientation of the flame normal and the wall normal, the flame can be either head-on or entrained. Outside of the influence zone the head-on flame elements are predominant, while inside the quenching zone flames are more likely to be entrained. The alignment relations among important vectors, including the principal axes of the strain rate tensor, the flame normal vector and vorticity have been investigated. Outside of the influence zone the normal vector of the progress variable isosurfaces aligns with the most extensive principle axis in the reaction zone and with the most compressive axis in the unburned and burned gas regions. Within the quenching zone, the preferential orientation with the most extensive principal axis disappears, once the flame dilatation and flame-normal strain rate decrease. Conditional alignment statistics demonstrate the distinctly different properties between the entrained flame and the head-on flame parts. In summary, the alignment relations are primarily determined by the relative strengths of chemical heat release, turbulent staining, and wall heat flux.