Implementing Radiation Model in Axisymmetric domain.
I am trying to model an radiation beam in an axisymmetric domain. The flow is laminar, and energy equation and DO-Radiation is switched on. The domain is rectangular in shape with the bottom wall as the axis of symmetry, and top wall as adiabatic. A small section at the inlet(not a part of it) adjacent to the axisymmetric wall is specified as irradiated wall. The absorption coefficient of the fluid is set to zero, however, I am unable to acheive a collimated beam, as the radiation intensity decreases with increasing axial distance without any attenuation specified by me. Any suggestions on the same?