A dynamic SGS combustion model based on fractal characteristics of turbulent premixed flames

Abstract

A dynamic subgrid scale (SGS) combustion model for large eddy simulation (LES) of turbulent premixed combustion is proposed. The model is based on fractal characteristics of turbulent premixed flames of the flamelet regimes and scale separation of turbulence. It dynamically calculates the fractal dimension of the flame surface by using the procedure given by the fractal dynamic SGS (FDSGS) combustion model. The procedure is locally applied to the flame surface and the local fractal dimension is evaluated. The local flame surface area is then computed by using the local fractal dimension, and the turbulent burning velocity is obtained assuming the flamelet concept. Validation of the model is done by using filtered direct numerical simulation (DNS) data of hydrogen-air turbulent premixed flames represented by a detailed kinetic mechanism of 12 reactive species and 27 elementary reactions. The configurations of the DNS are classified into the corrugated flamelets regime and the regime close to the boundary between the corrugated flamelets regime and the thin reaction zones regime. The Reynolds number based on the Taylor micro-scale is set to 97.1 for the both cases. The predictions of the developed SGS combustion model agree quite well with the DNS data. Furthermore, comparison of the present model with other conventional SGS combustion models demonstrates the superiority of the present model to them in terms of accuracy.