Pair Feature
A Pair Feature () is a special feature that defines conditions on pairs. A pair has a source and a destination side, and a pair condition typically connects the dependent variables between them using pointwise constraints.
The most common pair condition is the continuity pair condition, which simply makes the dependent variables equal on both sides. All physics interfaces gets this pair condition by default, so you do not have to add it.
This feature is useful to define other types of pair conditions. The major difference between a pair feature and an ordinary feature lies in subnodes that define selections.
For pair features, there are two extra options in the Selection list of the Selection section; Source and Destination. With these options you can specify to use the source or destination boundaries in the condition of a pair feature; see Specifying Selections for more information.
•
To add a Pair Feature under the Building Blocks branch, Features node: On the Physics Interface toolbar, select it from the More Features menu, or right-click Features and add it from the context menu.
•
To add a Pair Feature under the Physics Interface or Multiphysics Interface, Right-click the Physics Interface or Multiphysics Interface nodes to add this from the Features submenu.
Except for a few excluded sections, the Settings window is similar to the Generic Feature node.
Selection Settings
See Selection Settings for Generic Feature. For a pair feature, you do not have to specify the geometric entity level, because it is always boundary level. The same is true for the domain type setting, because all pairs belong to a special domain type, called Pair. Ordinary features that support this domain type also appear in a pair version among the physics interface’s pair conditions.
All pair features also have a special rule for overriding selections. They are always exclusive to all nonpair features preceding the pair in the list. For all features, pairs and nonpairs that lie below the pair in the list, contribute with the pair condition. As a result, you cannot set the override type for pair features.
Preferences
See Preferences. It is not possible to add a pair feature as a default feature to a physics interface.
•
Identifiers for the Generic Feature node
•
Identity and Contact Pairs in the COMSOL Multiphysics Reference Manual