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?



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