A novel formulation for the large-eddy simulation (LES) of turbulent combustion flows is presented. The formulation is based on coupling LES equations for mass and momentum, with the corresponding 1D stochastic governing equations using the One-Dimensional Turbulence (ODT) model. ODT domains, or elements, on which fine-grained ODT simulations are implemented, are embedded in the flow to represent unresolved scalar and momentum statistics. The formulation is designed to address important coupling between turbulent transport and molecular processes (reaction and diffusion) over a wide range of length and time scales. This coupling poses difficult challenges for the LES modeling of turbulent mixing and combustion flows. The LES-ODT approach is implemented for the problem of autoignition in non-homogeneous mixtures. The LES-ODT model yields excellent agreement with direct numerical simulations (DNS) of reactive scalars' statistics at different turbulence and Lewis number conditions. Comparisons of the LES-ODT results with DNS show that the model represents adequately turbulent transport through its filtered advection and stochastic stirring. Molecular transport exhibits important roles in determining the rate of heat and mass dissipation from the autoignition kernels and their propagation. IntroductionThe state-of-the-art approaches for the large-eddy simulation (LES) of turbulent combustion may be classified under the following three categories: (1) moment methods such as the ones based on the flamelet approach [43] and the conditional moment closure (CMC) approach [34], (2) filtered mass-density function (FDF) methods [16,45], and (3) one-dimensional stochastic approaches, such as the linear-eddy model (LEM) [25] and the one-dimensional turbulence (ODT) model [29]. In moment methods, reactive scalar closure for source terms or scalar moments are resolved in a reduced parameter space; moments for these parameters are transported within the context of the LES governing equations. Important limitations have already been recognised for moment approaches as related to the adequacy of a limited number of moments to predict non-equilibrium effects, such as extinction and reignition, the
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