If you wanted to model a filter in an airflow using CFD, how would you go about it? I imagine that an exact model of a filter would be way too complex to model and take vast amounts of time to solve, so there must be some kind of simplification? I was thinking that maybe some known properties of a filter could be applied as an input to the airflow. But the question is then, how do these filter properties become known? Experimentally? Another CFD program? And that's assuming that that actually is the method for solving! Also, can anybody recommend some decent reading material on filters and CFD and filters?