The Fluid and Matrix Properties node adds the equations for Darcy’s law (excluding any mass sources), and contains settings for the fluid properties and the porous matrix properties such as the effective porosity.

These settings can only be edited if the Fluid and Matrix Properties node was added manually. For the default node, the same settings as in the Shell Properties section of the parent interface are applied.

If you clear the Use all layers checkbox, you can select individual layers within one layered material. If you have defined more than one layered material in the model, this means that you would have to add another boundary node to define the physics in the remaining material sections.

This section has fields and values that are inputs to expressions that define material properties. If such user-defined property groups are added, the model inputs appear here. The default model input is the temperature T and the absolute pressure pA.

For Fluid material you can select Boundary material (the default) to use the material defined on the boundary, or another material from the list to use that material’s properties for the fluid.

Specify the density and dynamic viscosity as described in the Fluid section of The Darcy’s Law Interface.

For the porous matrix material, select either Boundary material from the Porous material list (the default) to use the material defined for the porous domain, or select another material to use that material’s properties.

The matrix properties are defined as in The Darcy’s Law Interface, so take a look at the Matrix Properties section for details.