When defining a surface-to-surface radiation model, for the boundaries that radiate only on one side, it is important to make sure each radiating surface receives radiation only on its radiating side. A boundary that radiates on one side should not receive radiation on its back. An optional topology check is enabled by default for the Hemicube and Ray Shooting methods. If it detects that the back side of a radiating boundary can be seen from a point computing the irradiation a warning message is displayed. This may be due to erroneous definition of the boundary radiation directions or the opacity of the adjacent domains. The rad.Fbacksided_res and rad.Fbacksideu_res variables can be plotted to verify the locations where the problem has been detected. One can find them in the plot menu of a Surface-to-Surface Radiation or a Orbital Thermal Loads interface, in the Consistency check section.

This may also be due to the combination of a relatively coarse mesh with the High order mesh elements option selected in the interface settings. Conversely, quadrilateral mesh elements combined with curved boundaries can create inconsistencies in view factor calculations when High-order mesh elements is not selected.

Note that checking the model consistency does not require additional computational time when the Ray shooting method is used. In order to speed up the computation, in particular with the Hemicube method, once the configuration has been verified, it is recommended to deselect Check consistency option.