5002 SGS Modeling of Hierarchical Structures in Turbulent Premixed Flames

Abstract

A new SGS combustion model is proposed based on hierarchical structure of turbulent premixed flames. The hierarchical structure is clarified by the detailed analysis of direct numerical simulation (DNS) data of three-dimensional hydrogen-air turbulent premixed flame. SGS flame surface area strongly correlates with GS strain rate of turbulent velocity field, which is related to the cluster of coherent fine scale eddy. As the GS strain rate of the turbulent combustion field includes dilatation effects intrinsically, a physical consideration is introduced to give the lower limit of dilatation effects in GS. To represent the relation between GS flame surface area and GS strain rate, a new SGS combustion model is proposed under assumptions of fractal characteristics of flame fronts and the scale separation of turbulence. The results predicted by the proposed model coincide very well with DNS results.