Dynamically-dominant Subfilter-scale content for application to LES of Turbulence-Flame Interactions in Premixed Turbulent Combustion

In premixed turbulent combustion with strong turbulence, reaction-rate dynamics and heat release concentrate near thin front-like ``reaction zone'' regions with characteristic thickness at diffusion scales that are largely unresolved in large-eddy simulation (LES). Particularly problematic is the prediction of resolved-scale (RS) evolution of the third-order chemical nonlinearities associated with the local generation of species concentrations and thermal energy and second-order advective nonlinearities driven by space-time evolution of momentum within strong turbulence localized to sheet-like reaction zones that are largely unresolved by the LES grid. Using DNS of the interaction between a flame and arrays of rectilinear vortices, we describe the extraction of ``dynamically dominant'' subfilter-scale (SFS) structure near reaction zone sheets and the encapsulation of that structure within physics-based mathematical forms. We quantify the potential increase in accuracy in the application of these ``basis functions'' within the chemical and advective nonlinearities in the evolution of RS momentum, species concentration and thermal energy within the framework of large-eddy simulation. \textit{Supported by AFOSR.}