COMSOL 6.4 - Thin Barrier (Multiphysics Coupling)

) interface contains an optional multiphysics coupling feature on edges (in 2D) or surfaces (in 3D). The coupling node can be used to avoid meshing interior permeable structures that are less permeable than the adjacent porous domains. It links bidirectionally the and interfaces.

The is the default multiphysics coupling feature name.

The default (for the first multiphysics coupling feature in the model) is tbls1.

When nodes are added from the context menu, you can select (the default) from the list to choose specific boundaries, or select as needed.

This section controls which individual interfaces are coupled by the current coupling feature. 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 correct physics interface again from the or lists

The multiphysics coupling feature is designed to be only applicable for a . Select the to be used for the thin barrier from the list. The of the thin barrier is set in the section of the window of the . Also use this section to set the number of that are used in the Extra Dimension to solve the equations through the thickness of the thin barrier layer.

The material properties of the different phases, such as density and viscosity, can be defined through user inputs, variables, or by selecting a boundary material. For the latter option, additional inputs, for example temperature or pressure, may be required to define these properties. These model inputs appear in this section.

Select the material to use as porous matrix inside the thin barrier. Select (the default) from the list to use the material defined for the thin barrier boundary. Select another material to use that material’s properties.

The default εp (a dimensionless number between 0 and 1) uses the value , defined by the selected. For the default is 0.5.

The default κ (SI unit: m2) uses the value , as defined by the selected. For the default is 1e-9 m2.

Select a — (the default), , , or . The and options are only available when there are not more than two phases present in the model.

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For , enter an expression for the pc (SI unit: Pa) for the phases that are not computed from the volume constraint. The pressure of the corresponding phase is equal to the pressure of the phase computed from the volume constraint plus the capillary pressure supplied for this phase.

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For , enter an pec (SI unit: Pa), the mvG (dimensionless), and lvG (dimensionless).

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For , enter an pec (SI unit: Pa) and the λp (dimensionless).

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For , enter a capillary diffusion coefficient Dc (SI unit: m2/s) for the phases that are not computed from the volume constraint.

Select the material to use for each phase. Select (the default) from the list to use the material defined for the domain. Select another material to use that material’s properties.

Enter the ρ (SI unit: kg/m3), μ (SI unit: Pa·s) and κr (a dimensionless number between 0 and 1) for each phase. The defaults for the and are , and for the . For , the default values are 1000 kg/m3, 0.001 Pa·s. and

, respectively.

The input fields are only available when the is set to or . In the other cases ( or ) the relative permeabilities are defined by the or model. For the and model, specify the sri (dimensionless, default value 0) for each phase.