there are other ways to define porous mediums, check the help
but i think they all need porosity
but even then, if your provider doesn't have porosity, will they have other properties to set it up differently?
the effect that porosity has is on velocity
so you may have to do some physical tests to come up with porosity to match whats happening in the simulation
however from what i remember, it only affects velocity inside the porous medium but that is something you could check pretty easily in flow simulation
You are right that there are other ways of setting up the porous mediums, and they all require entering a porosity. My supplier has been able to provide data for the flow rates and pressure drops, but I'm concerned that the guess at porosity is creating inaccurate results. The goal of the project is to create laminar flow through a channel within a target velocity range (not specifically within the filter), so as long as the porosity does not affect the velocity before and after the filter then I should be good no matter what porosity I use, right?
setup a test case and look at how porosity affects things and then make a decision based on a known solution