The Thin Barrier, Interface condition models interior permeable interfaces like membranes, permeable walls, geotextiles, or perforated plates as thin permeable barriers. It can only be applied on interior interfaces of layered shells.

where n is the vector normal to the interface, u the Darcy velocity, ρ the density and p the pressure. Subscript d denotes the downside of the interface, and u denotes the upside of the interface. κb is the permeability of the thin barrier material, db the barrier thickness.

Set the interface for which the Thin Barrier, Interface node should be specified. Note that it can only be applied to interior interfaces of layered shells.

The settings are the same as for the Interface Selection section of the Interior Wall, Interface node.

The Global coordinate system is selected by default. The Coordinate system list contains any additional coordinate systems that the model includes. It can be used when prescribing the direction of the interface normal and of the velocity.

Enter a value or expression for the Permeability κb (SI unit: m2). The default Permeability κb uses the value From material. For User defined select Isotropic to define a scalar value or Diagonal, Symmetric, or Full to define a tensor value and enter another value or expression in the field or matrix.

Enter a value or expression for the Thickness db (SI unit: m, the default is 0.1 m).