Thin-Film and Porous Media Flow (Multiphysics Coupling)
The Thin-Film and Porous Media Flow multiphysics coupling node () links bidirectionally the Thin-Film Flow and Darcy’s Law interfaces.
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 (for the first multiphysics coupling feature in the model) is tfpf1.
Boundary Selection
When nodes are added from the context menu, you can select Manual (the default) from the Selection list to choose specific boundaries to define the multiphase flow coupling, or select All boundaries as needed.
When Thin-Film and Porous Media Flow multiphysics coupling node is added by the predefined Thin-Film and Porous Media Flow interface, the selection is the intersection of selections of boundaries of the participating physics interfaces.
Only boundaries that belong to the participating physics interfaces (which are chosen from the Coupled Interfaces selection list) can be selected.
Coupled Interfaces
This section defines the physics involved in the multiphysics coupling. The Thin-film flow and Porous media flow 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 (Mac 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 Multiphase Flow in Porous Media node from a physics interface. If the physics interface is removed from the Model Builder, for example Darcy’s Law is deleted, then the Porous media flow list defaults to None as there is nothing to couple to.
Coupling
This section defines the options available for the Coupling type between the Thin-film flow interface and the Porous media flow interface.
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Choose No-slip condition if the fluid velocity in the Porous media flow interface and the fluid velocities at the wall and base of the Thin-film flow interface are mutually independent. The coupling does not introduce additional velocity constraints in the Thin-film flow interface. However, it ensures the continuity of pressure and accounts for mass flux across the interface.
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Choose Beavers-Joseph slip condition if the development of the boundary layer at the intersection of the physics interfaces needs to be modeled using a small interface slip velocity. The coupling introduces constraints on the fluid velocities at the wall and base in the Thin-film flow interface which depend on the fluid velocity in the Porous media flow interface. Additionally, it ensures the continuity of pressure and accounts for mass flux across the interface. This option is only available when the Film flow model selected in the Fluid Film Properties of the Thin-film flow interface is either No-slip walls or Slip at walls. Also, specify the Beavers–Joseph slip coefficient at the wall and the base boundaries.
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Theory for the Thin-Film Flow Interfaces
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Theory for the Darcy’s Law Interface
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Theory for the Thin-Film and Porous Media Flow Interface
Squeeze Film Between Rectangular Porous and Nonporous Plates: Application Library path CFD_Module/Verification_Examples/squeeze_film_porous
Self-Lubricating Journal Bearing: Application Library path CFD_Module/Verification_Examples/self_lubricating_bearing