When modeling a semitransparent medium, it can be important to account for radiation that is internal to the fluid. Ansys Polyflow allows you to model internal radiation using the discrete ordinates (DO) model. The DO model requires a fixed geometry domain, in which the mesh encapsulates the radiative domain. Note that the DO model does not perform ray tracing.

The DO model can achieve more accurate results than those achieved by specifying the Rosseland correction at the boundary (see Radiative (Rosseland) Correction), but it is more expensive computationally. When you apply the DO model on a domain via an internal radiation sub-task, you should not apply the Rosseland correction to any of the boundaries.