In this paper the influence of radiation heat transfer in mixed convection buoyant turbulent flows is considered. The results show that in thermal driven flows radiation heat transfer is an essential part of the total flow system and must be considered for accurate flow predictions. A parallel
ethod (DTRM), which simulates surface to surface radiation heat transfer, is coupled with the DLR THETA code, an unstructured incompressible Navier-Stokes-Solver developed by the German Aerospace Center (DLR). The THETA code supports convective heat transport, very large grids, high complex geometries and massive parallel computations.