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.

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A general review of turbulent combustion modeling closures applicable to large eddy simulations (LES) is provided. The focus is on "regime-independent" models able to provide turbulent combustion closures ranging from purely premixed to purely non-premixed and all regimes between these two limits. Special emphasis is placed on primary propulsion applications, including liquid rocket engines, diesel engines, gas turbines, and scramjets. These applications span a large range of physical phenomena including both ideal-and real-gas behavior, single-phase and multi-phase combustion, relatively low Mach number to supersonic and hypersonic combustion, and relatively simple geometries to highly complex geometries. Three classes of models are identified as possibly providing such broad based modeling closures: flamelet-library/presumed probability density function (PDF) models, linear eddy based models (LEM), and transported PDF or filtered density function (FDF) based models. This review focuses both on fundamental physical assumptions that apply across all of the models and assumptions that apply to each of the models individually. Namely, assumptions regarding the presumed size of the large dimensional turbulent scalar manifold apply to all of the models; however, flamelet models almost always presume only a few dimensions are necessary to yield adequate representation of the larger, turbulent manifold. In contrast, LEM and FDF models are not, in theory, bound by any manifold size assumptions (i.e. direct calculation of the turbulent scalar manifold is possible); however, due to current computational limitations, these models often employ manifold reduction techniques which are usually not as restrictive as those used by flamelet models. Individual assumptions associated with the specific formulation of each model are also analyzed. From these discussions, additional novel results testing some of the fundamental physical assumptions associated with each model are provided from a unique database of DNS of high pressure turbulent reacting temporally developing shear flames. The DNS database includes simulations of H2/O2, H2/Air, and Kerosene/Air flames with both detailed and reduced chemistry. The DNS include real property models, a real-gas equation of state, and generalized heat and mass diffusion derived from non-equilibrium thermodynamics. The simulations span a large range of Reynolds numbers and pressures (up to 125 atm), with resolutions approaching 1 billion grid points. Finally, some general comments towards the future challenges related to LES combustion modeling are offered. NomenclatureA m , B m = mixture parameters for the equation of state C Ω = modeling constant dW = differential increment of the Wiener process D = molecular diffusivitytotal energy (internal plus kinetic) E = modeling term F L = filtered mass density function F stir = triplet mapping advection model G = filter kernel H ,α = partial molar enthalpy of species α J i,α = mass flux vector of species α k sgs = subgrid turbulence kinetic energy M...

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