Model inputs can appear in an equation node’s or material model node’s
Model Inputs section. Model inputs are fields such as temperature and velocities that act as inputs for material models and model equations. They appear in the
Model Inputs section if a material is defined so that a material property becomes a function of the temperature, for example. COMSOL Multiphysics connects the model input to an existing field (dependent variable) within the physics interface (but not to available fields in other physics interfaces). For common multiphysics couplings, predefined multiphysics couplings are available under the
Multiphysics node (see
The Multiphysics Node). The following section is mostly useful for cases when such predefined couplings are not available.
With more than one physics interface in the model, coupling of the fields is easy: all applicable fields that can serve as inputs in another physics interface automatically appear in the other physics interface’s Settings window’s
Model Inputs section. For example, with a Heat Transfer in Fluids (ht) interface and a Laminar Flow (spf) interface, you can select
Velocity field (spf), which the
Fluid Properties 1 {fp1} node in the
Laminar Flow branch defines, from the
Velocity field list in the
Model Inputs section of the
Settings window for
Heat Transfer in Fluids. For a coupling in the other direction (if you use temperature-dependent fluid properties, for example), you can select
Temperature (ht) from the
Temperature list in the
Model Inputs section of the
Settings window for
Fluid Properties.
When you have selected a model input from one of the lists, click the Go to Source button (
) next to the list to move directly to the node in the other physics interface that provides the model input. If more than one node contribute to the model input, choose which one to got to in the
Contributing Entities dialog box. Then click
OK to move to the selected node.
A list in the Model Inputs section becomes unavailable if the physics itself defines the field because it is then automatically connected to that field. For example, with a Heat Transfer in Fluids (ht) interface the
Temperature list is unavailable in the
Heat Transfer in Fluids 1 {fluid1} node. This automatic connection selects the
Temperature (ht) field. As long as the list is unavailable, you cannot change it. If you want to use another temperature field or an expression, you first make the list editable by clicking the
Make All Model Inputs Editable button (
).
