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Hi. I am studying about porous media modeling. From Ergun equation
Rv = [150*(1-e)^2/phi^2*D^2*e^3]
and
Ri = [2*1.75*(1-e)/phi*D*e^3]
where Rv and Ri are viscous resistance and inertial resistance, respectively, and they are input parameters into fluent for porous media. As can be seen these equations depend on Porosity (e).
My question is, if the above equations include "e" (porosity) then why in Fluent "Porous Zone" there is a separate input space for Fluid Porosity. Is this porosity different from the one in the equations?

I also modeled a 2d tube as porous media and assigned some fixed value to Rv and Ri. I checked with different "Fluid Porosity" but found no effect on results.
Please if someone can explain. Thanks