Fluid-Pipe Interaction
The Fluid-Pipe Interaction () multiphysics node provides a way to transfer fluid loads from the Pipe Flow interface to the Pipe Mechanics interface.
Settings
The Label is the multiphysics coupling feature name. The default Label (for the first multiphysics coupling feature in the model) is Fluid-Pipe Interaction 1.
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 fpipe1.
Edge Selection
By default, the selection is set to All edges. However, only edges that belong to both the Pipe Flow and Pipe Mechanics interfaces are applicable. This is deduced automatically using the selections made on the coupled physics interfaces.
Coupled Interfaces
This section defines the physics interfaces involved in the coupling. The Fluid and Structure lists include all applicable physics interfaces.
The default values depend on how the node is created.
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.
If it is added automatically when the physics interface is chosen 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 Fluid-Pipe Interaction node from a physics interface. If the physics interface is removed from the Model Builder, for example Pipe Mechanics is deleted, then the Structure 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 re-establish the coupling, you need to choose the physics interface again from the lists. This is applicable to all multiphysics coupling nodes that would normally default to the once present physics interface. See Multiphysics Modeling Workflow in the COMSOL Multiphysics Reference Manual.
Fluid Load
In this section, you specify the load contributions that are transferred from the Pipe Flow interface to the Pipe Mechanics interface.
Select the Drag Force check box to include the forces from viscous drag along the pipe.
Select the Centrifugal Force check box to include centrifugal forces from the fluid in curved pipes.
Select the Pipe flow pressure check box to include effects of the internal pressure in the pipe. When Pipe flow pressure is selected, you can also enter an external pressure. Select a method for entering the External pressure, po, — User defined or Common model input.
For User defined, enter a value or an expression for the external pressure.
Select the Junction forces check box to include local forces occurring at various connections and components in the piping system.
The check boxes in this section interact with any Fluid Load node on the same selection. When a check box is selected, the corresponding entry in the Fluid Load node is made unavailable.