A priori analysis of subgrid mass diffusion vectors in high pressure turbulent hydrogen/oxygen reacting shear layer flames

Abstract

Evaluation of an unsteady flamelet progress variable model for autoignition and flame development in compositionally stratified mixtures Phys. Fluids 24, 075115 (2012) Intermittency in premixed turbulent reacting flows Phys. Fluids 24, 075111 (2012) Recirculation zone dynamics of a transversely excited swirl flow and flame Phys. Fluids 24, 075107 (2012) Short-term prediction of dynamical behavior of flame front instability induced by radiative heat loss Chaos 22, 033106 (2012) Route to chaos for combustion instability in ducted laminar premixed flames Chaos 22, 023129 (2012) Additional information on Phys. Fluids Direct numerical simulations of high pressure (100 atm), turbulent H 2 /O 2 nonpremixed temporally developing shear layer flames are conducted at initial Reynolds numbers ranging from 850 ≥ Re δ0 ≥ 4500, with up to ∼3/4 ×10 9 grid points. A real gas equation of state, real property models, detailed chemistry, and generalized diffusion models are included. The results of the simulations focus on the mass diffusion vectors and their subgrid contributions relevant to large eddy simulation of turbulent combustion. Comparisons of the actual filtered mass flux vectors with their corresponding forms evaluated with filtered primitive variables are shown through correlation coefficients, probability density functions (PDFs) of the ratios between the vector magnitudes, and PDFs of the angles between the vectors. The results show a reasonable correlation (≥0.75) for all species and simulations when evaluated globally. However, the correlations weaken substantially in regions of large temperature subgrid scale (SGS) variance and filtered SGS scalar dissipation. Within these regions, the correlations are also shown to vary inversely with Reynolds number. Vector analysis indicates that evaluating the mass flux vector using only the filtered primitive variables accurately predicts the direction of the actual filtered flux; however, the magnitude is poorly predicted in the aforementioned regions. Comparisons of the subgrid mass fluxes to the subgrid scalar fluxes are also represented as PDFs of the ratios between the vector magnitudes. These results show the subgrid mass flux to be significantly smaller ( 5%) than the subgrid scalar flux, and this ratio is shown to diminish with increasing Reynolds number. A final comparison of the divergence of the subgrid mass fluxes to the subgrid scalar fluxes are also represented as PDFs of the ratios between the magnitudes. At lower Reynolds numbers, these ratios suggest comparable values between the subgrid diffusion and turbulent stirring terms in regions of large temperature SGS variance and filtered SGS scalar dissipation. However, this ratio is shown to diminish, but remain significant, with increasing Reynolds number. C 2012 American Institute of Physics. [http://dx.

Numerical Benchmark for High-Reynolds-Number Supercritical Flows with Large Density Gradients

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