The Porous Medium node adds the equations for modeling flow through porous domains. By default these are
Equation 7-1 and
Equation 7-2 (excluding any mass sources).
The Porous Medium feature has two default subfeatures — the
Fluid subfeature where the fluid density
ρ(SI unit: kg/m
3) and dynamic 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.
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.
where the nonlinear parameter β (SI unit: 1/m) is further specified in the
Porous Matrix subfeature.
Equation 7-1 can also be formulated with respect to a storage term.
The storage coefficient S can be interpreted as the weighted compressibility of the porous material and the fluid. Define the time dependent storage term by selecting one of the following options from the drop-down menu:
Note that the option to choose a different Flow model and
Storage model is only available in some modules. For a detailed overview of the functionality available in each product, visit
https://www.comsol.com/products/specifications/.