A Priori Assessment of Two-Level Simulation Model for Numerical Investigation of Turbulent Premixed Flames

Turbulent premixed flames are marked by the presence of large-scale (LS) and small-scale (SS) processes and their interactions in form of chemical reactions, molecular and turbulent mixing, convective processes, and thermal expansion, which makes computational modeling a challenging task. In this study, the two-level simulation (TLS) modeling strategy developed earlier for incompressible turbulent flows and passive scalar mixing in such flows is assessed for its capabilities to model turbulent premixed flames. In comparison to the conventional large-eddy simulation (LES) strategy, where the effects of the unresolved small-scales of motion on the large-scales of motion are modeled by employing subgrid-scale (SGS) closures, in the TLS model, both large- and small-scales are explicitly evolved in a coupled manner. In the present study, a comprehensive a priori assessment of the TLS model is performed using direct numerical simulation (DNS) datasets corresponding to two canonical temporally evolving methane/air turbulent premixed flames. The assessment is carried out in terms of examining the behavior of the large- and the small-scales of the reacting flow field in the physical and the spectral space, verifying the modeling assumptions, and analyzing the prediction of SS quantities relevant for modeling of such flames such as the scalar dissipation rate and counter-gradient turbulent transport.