COUNTER-GRADIENT DIFFUSION IN A CONFINED TURBULENT PREMIXED FLAME

In the present study, we develop a full second order model and a new f lamelet closure relation for the mean chemical source term to describe turbulent reactive flows with premixed reactants. This description en sures that non-gradient and counter-gradient diffusion which can appea r In such flames, are taken into account in 2-D or 3-D geometries. 2-D calculations are performed in the case of a confined turbulent premix ed flame stabilized by a backward Facing step, a configuration which r eveals experimentally counter-gradient diffusion and combustion induce d production of turbulence. Numerical results are found to be in excel lent agreement with measurements of Shepherd et al, [Nineteenth Sympos ium (International) on Combustion (The Combustion Institute, Pittsburg h, 1982)]. The important Influence of counter-gradient diffusion on fi rst order quantities, i.e,. mean velocity and length of the recirculat ion zone is shown. (C) 1997 American Institute of Physics.