There are two ways to create and use the available predefined multiphysics couplings: using Predefined Multiphysics Interfaces or
Adding Predefined Multiphysics Couplings to Physics Interfaces using
The Add Multiphysics Window or in
The Multiphysics Branch. You can also create multiphysics couplings, in the physics interface settings, using a model input or by directly typing an expression using a dependent variable from another physics interface, for example (see
Specifying Equation Coefficients and Material Properties for information about what you can include in such expressions).
The Joule Heating Interface is an example of a predefined multiphysics interface. Many other multiphysics interfaces are available depending on the products included in your COMSOL license. After
Joule Heating is selected from
The Model Wizard, the
Heat Transfer in Solids interface, the
Electric Currents interface, and a
Multiphysics node, including the default feature applicable to the multiphysics coupling (
Electromagnetic Heating), are displayed under the
Added physics interfaces list as in
Figure 3-14.
Figure 3-15 shows you what is included in the Model Builder when a predefined multiphysics interface is added. Compare to
Figure 3-16 where individual physics interfaces are added, and these features are initially accessible only from the context menu. There can also be moving mesh nodes added as part of a multiphysics interface; they then appear under
Definitions in the
Added physics interfaces list.
An empty Multiphysics node is added automatically when two (or more) physics interfaces are set up in a model and when there is the possibility to couple the physics interfaces. In other words, if you add physics interfaces one at a time, and the software identifies these physics interfaces as being of the multiphysics category, the
Multiphysics node is automatically added to the Model Builder. The relevant predefined multiphysics coupling features are then available from the context menu (right-click the
Multiphysics node) as well as from the
Physics toolbar, in the
Multiphysics menu. See
Figure 3-16. You can also add predefined multiphysics couplings from the
Add Multiphysics window (see
The Add Multiphysics Window), which then adds all necessary multiphysics coupling nodes under the
Multiphysics node. Using a workflow where you add physics interfaces and multiphysics couplings manually makes it possible to analyze and validate one physics at the time before solving the full multiphysics model.