Subgrid Combustion Modeling for Premixed Turbulent Reacting Flows *

Two combustion models for turbulent premixed combustion in the flamelet regime are developed for unsteady simulations. The first model is a convensional G equation flamelet model and the main issues discussed are the subgrid closure. The second model is based on the Linear-Eddy Model. Both models are used in simulation of turbulent stagnation point flames. The heat release and turbulence intensity are varied. Time averaged statistics from convensional simulations show good qualitative agreement with experiments and the normalized turbulent flame speed agrees well with the experimental data. Counter-gradient scalar diffusion is observed in high heat release, low turbulence intensity flames. This raises the question about how important the gradient diffusion approximation is to these results. Preliminary results from LES-LEM simulations involving moderate heat release and high turbulence intensities are reported. The key role of the front tracking algorithm is demonstrated. Qualitative trends in the burning rates with varying turbulence intensity is also demonstrated.