# Porous Materials

I am trying to simulate air flowing though a 1/4 inch wire mesh that uses wire of a diameter of about 1/16th of an inch.

There are 3 factors to adjust for the porous material but it is not clear to me how they apply.

Are they constants for a second order polynomial that represent pressure drop as a function of fluid velocity?

Thanks

Ken

### Thin Porous Media

For a thin porous medium, as in this case, you need to apply the Conditions->Porous tool to a both sides of a double-sided face. It can be tricky to get the geometry correct:

1. Make sure the edges of the porous face are part of the enclosing volume - assuming the edges of the porous face touch the surrounding faces within the volume
2. In Caedium you need to use the Edges->Connect tool to connect the edges of the porous face with the identical edges in the surrounding volume
3. Use the Booleans->Subtract tool with the Topology Only option enabled to subtract the porous face from the surrounding volume
4. Use the Faces->2-Sided tool to make the porous face double sided

You need to assign the Conditions->Porous to both sides of the porous face (i.e., the face and its shadow).

The parameters for a thin porous face are:

• L - Porous material thickness
• d - 1 / permeability (k), in Darcy's Law
• f - 2 / inertial permeability (k1), in Darcy's Law with Forchheimer term, sometimes referred to as inertial resistance (C2)

Note these descriptions are presented in Caedium as tooltips when you left-click the respective properties and are displayed in the status bar - bottom left hand of the application.

Darcy's law is a universal way to present a porous material. In terms of a power law, this is only available for a volume-based porous medium.

So you have to relate your screen to a permeability factor using data on the screen from the manufacturer.

### Reference for porous media permeability

After some research it appears the go to reference for permeability of various porous media, including mesh screens is:
"Handbook of Hydraulic Resistance", I.E. Idelchik