| Direct Numerical Simulations (DNS) of high pressure, turbulent H2/O2 non-premixed flames employing real gas effects, detailed chemistry, multicomponent, differential, and cross diffusion are conducted. The results of these simulations are analyzed to provide important subgrid information relevant to Large Eddy Simulation (LES) of turbulent combustion. Subgrid filtered scalar dissipation and scalar variances, species concentrations, reaction rates, and flame temperature are presented as a function of mixture fraction. The analysis also includes a detailed comparison of the actual filtered mass flux vectors with their corresponding forms evaluated with the filtered primitive variables. The results show a reasonable correlation when evaluated globally. However, the correlations weaken substantially in regions of large subgrid kinetic energy, subgrid mixture fraction variance, subgrid temperature variance, and subgrid scalar dissipation. This suggests that much weaker global correlations may occur in more realistic high Reynolds number flames. Vector analysis indicates that modeling the mass flux vector using only the filtered variables tends to accurately predict the direction of the filtered flux, however, the magnitude is poorly predicted in the aforementioned regions. The results provide important physical insight into the subgrid and suggest future modeling efforts are needed to accurately predict the filtered mass flux vector in LES of combustion. |
