Periodic Condition

Use a Periodic Condition to prescribe that the displacements on two different sets of boundaries with the same geometrical shape are related, as in a periodic structure.

Several different types of periodicity properties of the solution can be prescribed using this boundary condition. The Continuity, Antiperiodicity, and User defined periodic conditions directly prescribe relations between displacements and can be used for any type of study.

The two sets of boundaries between which there is a periodicity condition are called the source and destination respectively. It is not required to have the same mesh on the source and destination, but the local accuracy of the solution at the boundaries will be better if you use the same mesh.

Boundary Selection

Select both the source and destination boundaries.

The software automatically identifies the boundaries as either source boundaries or destination boundaries. This works fine for cases like opposing parallel boundaries. In more general cases, use the Destination Selection subnode to specify the boundaries that constitute the destination. By default this node contains the selection that COMSOL Multiphysics has identified.

In cases where the periodic boundary is split into several boundaries within the geometry, it might be necessary to apply separate periodic conditions to each pair of geometry boundaries for the matching to work properly.

Periodicity Settings

With Type of periodicity you select the form of periodicity that your solution should have.

•	For Continuity, the displacements on the destination are set equal to the displacements on the source; . If the source and destination boundaries are rotated with respect to each other, a transformation is automatically performed, so that corresponding displacement components are connected.

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For Antiperiodicity, the displacements on the destination are set equal to the displacements on the source with the sign reversed; . If the source and destination boundaries are rotated with respect to each other, a transformation is automatically performed, so that corresponding displacement components are connected.

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For User defined, select the check box for any of the displacement components as needed. Then for each selection, choose the Type of periodicity—Continuity or Antiperiodicity. Each selected displacement component will be connected by or respectively. If the source and destination boundaries are rotated with respect to each other, a transformation is automatically performed, so that corresponding displacement components are connected.

Constraint Settings

To display this section, click the Show button () and select Advanced Physics Options.

Orientation of Source

For information about the Orientation of Source section, see Orientation of Source and Destination.

Location in User Interface

Context Menus

Solid Mechanics>Connections>Periodic Condition

Solid Mechanics>Connections>Periodic Condition>Destination Selection

Ribbon

Physics Tab with Solid Mechanics selected:
Boundaries >Connections>Periodic Condition

Physics Tab with Periodic Condition node selected in the model tree:
Attributes>Destination Selection