Some recent developments in the theory of premixed turbulent flames

The application to the description of premixed turbulent flames of simple geometry of a recently developed theory based on second order closure and avoiding gradient transport assumptions throughout, is reviewed. It is shown that the gradient normal to the flame of the mean pressure acts differentially on parcels of heavy reactant and light product to cause significant effects absent in constant density turbulence; countergradient diffusion and the production of turbulent kinetic energy. A similar phenomena is predicted for oblique flames with undeflected mean streamlines; in this case the gradient tangent to the flame of the Reynolds stress acts differentially so as to cause parcels of reactant and product to follow mean streamlines which differ from one another and from the mean streamline. The implications of these results for experimental combustion research and for the development or predictive methods for turbulent combustion are emphasized