On the modeling of the filtered radiative transfer equation in large eddy simulations of lab-scale sooting turbulent diffusion flames

This study investigates the influence of some approximations on the modeling of the filtered absorption and emission terms in an ethylene/air turbulent jet flame. Filtered radiative quantities along characteristic diametric optical paths are computed from corresponding instantaneous radiative quantities obtained by using a stochastic space and time series model. Model results show that the subgrid-scale radiative absorption can be disregarded whatever the filter size. The effects of subgrid-scale fluctuations on the filtered emission term are dominated by the subgrid-scale absorption coefficient-blackbody intensity correlation and the subgrid-scale temperature self-correlation. The former reduces the filtered emission term in regions where soot radiation dominates and enhances it in regions where gas radiation prevails. The latter always increases the filtered emission term. For a filter size typical of engineering applications, model results suggest that the effects subgrid-scale fluctuations on the filtered emission term have to be modeled.