Poroelasticity, Layered (Multiphysics Coupling)
The Poroelasticity, Layered multiphysics coupling node () links bidirectionally the Layered Shell and Layered Darcy’s Law interfaces to account for poroelastic deformation on layered shells.
Settings
The Label is the default multiphysics coupling feature name.
The Name is used primarily as a scope prefix for variables defined by the coupling node. Refer to such variables in expressions using the pattern <name>.<variable_name>. In order to distinguish between variables belonging to different coupling nodes or physics interfaces, the name string must be unique. Only letters, numbers, and underscores (_) are permitted in the Name field. The first character must be a letter.
The default Name is poro, followed by the number of defined multiphysics couplings, that is poro1 for the first multiphysics coupling feature in the model.
Boundary Selection
When Poroelasticity, Layered is added to the Multiphysics node as an effect of adding a Poroelasticity, Layered Shell interface, the selection is the same as for the participating physics interfaces. In the Boundary Selection menu you can choose between Manual and All boundaries, the latter being the default option. Note that only boundaries that are active in the physics interfaces selected in the Coupled Interfaces section can be selected.
Coupled Interfaces
This section defines the physics involved in the multiphysics coupling. The Layered shell and Flow in porous media lists include all applicable physics interfaces.
The default values depend on how the coupling node is created.
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If it is added from the Physics ribbon (Windows users), Physics contextual toolbar (macOS and Linux users), or context menu (all users), then the first physics interface of each type in the component is selected as the default.
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If it is added automatically when a multiphysics interface is selected in the Model Wizard or Add Physics window, then the two participating physics interfaces are selected.
You can also select None from either list to uncouple the Poroelasticity node from a physics interface. If the physics interface is removed from the Model Builder, for example Darcy’s Law is deleted, then the Flow in porous media list defaults to None as there is nothing to couple to.
If a physics interface is deleted and then added to the model again, then in order to reestablish the coupling, you need to choose the physics interface again from the Layered shell or Flow in porous media lists. This is applicable to all multiphysics coupling nodes that would normally default to the once present interface. See Multiphysics Modeling Workflow in the COMSOL Multiphysics Reference Manual.
Shell Properties
Here you select on which layers of a layered material the physics interface should be active. By default, the Use all layers checkbox is selected. This means that all layers in all layered materials on the selected boundaries are used.
If you clear the Use all layers checkbox, you can select individual layers within a single layered material. This means that the physics interface is restricted to the boundaries on which a specific layered material is defined.
For a general description of layer selections, see The Shell Properties and Interface Selection Sections in the Structural Mechanics Module User’s Guide.
Poroelastic Coupling Properties
In the Reference pressure level field, enter a reference pressure pref (SI unit: Pa) at which the pore pressure does not affect the porous matrix deformation. The default value is 1 atm.
For the Biot–Willis coefficient list, the default is to take its value From material. Choose User defined to enter a Biot–Willis coefficient αB (dimensionless) in the text field.