DNS and LES of turbulence–radiation interactions in canonical systems

A number of DNS and LES studies have focused on radiative heat transfer and turbulence–radiation interactions in canonical (highly idealized, and usually not physically realizable) turbulent reacting or nonreacting systems. In contrast to an actual combustion system or device, this allows direct manipulation and isolation of the physical processes of interest, and removes ambiguities in the interpretation of the results. While one must exercise caution in extrapolating the results from these highly simplified problems to practical turbulent flames, such investigations are useful for physics discovery and for providing data that can be used to develop and/or calibrate models that are subsequently applied to real turbulent flames and combustion devices. In this chapter, examples of DNS and LES studies of radiation and TRI in canonical configurations are presented and discussed. This includes some results for nonreacting systems, and studies with both uncoupled radiation (no feedback of the radiative source term into the CFD simulation) and with coupled radiation. Most experimental and modeling studies of TRI have focused on how turbulence affects radiative heat transfer, but the investigations with coupled radiation also allow one to explore at a fundamental level how radiation and TRI modify the structure of the turbulent flow field. These studies provide useful insight and guidance on what one should look for and expect in the more realistic turbulent reacting flows that are considered in the next two chapters.