Study of turbulence-radiation interactions in large-eddy simulation of scaled Sandia flame D

Abstract

The importance of the subgrid-scale contribution for computing the radiative source term in large-eddy simulations (LES) for the scaled Sandia flame D is studied in this work. This study is carried out by employing the flamelet generated manifolds approach as a combustion model in combination with the Eulerian stochastic field method to account for the turbulence-chemistry interaction. Furthermore, the finite volume method is employed to solve the radiative transfer equation with the non-grey weighted-sum-of-grey-gases (WSGG) model for the spectral resolution. In order to take thermal radiation into account in the LES context, the filtered radiative source term should be computed. The contribution of the resolved scales can be explicitly calculated, whereas the terms involving the subgrid-scale contributions are unclosed and require approximations. In this work, the optically thin fluctuation approximation is applied for modelling the filtered absorption term and different methods are used for computing the emission term, in which the subgrid-scales are either considered or omitted. The results show that the difference between the radiative source terms computed by accounting and by neglecting the subgrid-scale contribution is significant only in the regions where this term is small. Besides, no relevant differences are found in the profiles of mean temperature and CO2 species concentration calculated using those two different approaches. These results indicate that the subgrid-scale contribution may be neglected in the context of LES for the flame under consideration.