A numerical analysis of reaction-diffusion effects on species mixing rates in turbulent premixed methane-air combustion

Reactive scalar mixing time scale have been investigated in direct numerical simulation data for turbulent premixed Bunsen flames with reduced methane-air chemistry. Previous conclusions from single step chemistry studies are confirmed regarding the role of dilatation and turbulence-chemistry interactions on the progress variable dissipation rate. Compared to the progress variable, the mixing rates of intermediate species can be several times greater. The variation of species mixing rates are explained with reference to the structure of one-dimensional flamelets. A new model is produced for the ratios of scalar mixing time scales which can be applied, for example, in transported probability density function simulations