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.