Differential diffusion modelling in transported PDF simulations of turbulent flames

Honoring Ted O'Brien. The modelling strategy to incorporate differential diffusion effects in transported density function method (PDF), particularly in the context of large eddy simulation (LES) is proposed. Differential diffusion at the filter scale is resolved by the mean drift term in composition equations, while subgrid differential diffusion is modelled by the augmented mixing models that can account for differential mixing rates for each individual species. Both RANS/PDF and LES/FDF simulations of a jet-in-hot-coflow methane-hydrogen flame have been performed to investigate the effects of differential diffusion on flame characteristics.