The following guidelines are helpful when selecting solver settings for models that involve radiation in participating media or radiation in absorbing-scattering media, when solved with the discrete ordinates method. First check the Use reduced Jacobian setting in the Jacobian Contribution section of the Radiation in Participating Media or Radiation in Absorbing-Scattering Media interfaces. It is selected by default, which results in a lumped Jacobian matrix and reduces a lot the required amount of memory and the computation time. There are a few configurations where this formulation may lead to poor convergence. In this case, disabling the option should fix the issue at the price of a much larger memory consumption use, in particular when the number of directions of the quadrature set is large.

The default linear solver when using the discrete ordinates method is Direct, radiation variables. It is expected to be the fastest linear solver in most configurations, for a reasonable amount of memory thanks to the Use reduced Jacobian option. The AMG, radiation variables iterative solver can be preferred in case of memory limitations since it will reduce even more the memory requirements.