Direct numerical simulation of turbulence-radiation interactions in a statistically one-dimensional nonpremixed system

An important issue in chemically reacting turbulent flows is the interaction between turbulence and radiation (TRI), which arises from highly nonlinear coupling between fluctuations in temperature and species composition of the flow field with the fluctuations of radiative intensity. Here direct numerical simulation (DNS) has been employed to investigate TRI in canonical nonpremixed systems in three-dimensional geometries. A photon Monte Carlo method has been used to solve the radiative transfer equation (RTE), which has been coupled with the flow solver. Radiation properties employed here correspond to a nonscattering fictitious gray gas with a Planck-mean absorption coefficient, which mimics that of typical hydrocarbon-air combustion products. Individual contributions of emission and absorption TRI have been isolated and quantified. The temperature self-correlation, the absorption coefficient-Planck function correlation, and the absorption coefficient-intensity correlation have been examined for intermediate-to-large values of the optical thickness, and contributions from all three correlations were found significant but the relative importance of their contribution varies with optical thickness.