have you checked the solidworks knowledgebase in the customerportal? i believe there is a specific article on it. to which i believe the answer is that the fluid is always transparent with respect to radiation.
that being said, what is your specific application that requires this? and in fluent, which of these methods is used for the fluid absorbtion of radiation?
this should also be in the technical reference.
also regarding flow simluation not being a "professional" CFD code, i don't know if I agree. we see people from every level of company use it for many different problems. many of the names of companies that we work with are high technology and household names that i would consider professional. fluent may have some additional features for very specific situations, but those also come at a dollar cost and computational cost so they generally are grouped together. i'd say you;re talking about tools for designers and tools for analysts. but again, there are differences other than their names that put them in those groups.