The Periodic Condition node adds a periodic boundary condition that can be used to reduce the model size by using symmetries and periodicities in the geometry and physics interfaces being modeled. This feature works well for cases like opposing parallel boundaries. In other cases, use a Destination Selection subnode to control the destination. By default, it contains the selection that COMSOL Multiphysics identifies.
) and select Advanced Physics Options in the Show More Options dialog box. 
) and select Advanced Physics Options in the Show More Options dialog box. 