The Unsaturated Porous Medium node adds the Richards’ equation (
Equation 7-6) for flow in variably saturated porous media.
The Unsaturated Porous Medium feature has two default subfeatures — the Fluid subfeature where the fluid density
ρ(SI unit: kg/m
3) and viscosity
μ (SI unit: Pa·s) are defined and the
Porous Matrix subfeature where the permeability
κ (SI unit: m
2)and porosity
εp (dimensionless) are specified as well as the retention model.
Select a coordinate system from the Coordinate system list for the interpretation of directions in anisotropic material properties. The default is the
Global coordinate system, and the list contains any additional orthonormal coordinate system (except boundary coordinate systems) added under the
Definitions node.
The subnodes inherit these coordinate system settings. In particular, the Permeability or
Hydraulic conductivity (in the
Porous Matrix subnode) should be set according to the coordinate system selected in this section.