Periodic Condition

The Periodic Condition node for this physics interface splits its selection in two groups: one source group and one destination group. Displacements and/or Electric Potentials on the destination boundaries are set equal to those on the corresponding source boundary. This corresponds to a situation where the geometry is a periodic part of a larger geometry. If the boundaries are not parallel to each other, the periodic dependent variable is automatically transformed.

The feature sets ui(x0) = ui(x1) for a displacement ui or similarly for the electric potential. The Periodic Condition splits its selection in two groups: one source group and one destination group. If two boundaries are selected COMSOL Multiphysics automatically assigns one boundary as the source and the other as the destination. To manually set the destination selection, for example if more than two boundaries are selected, add a subnode, which is available from the context menu (right-click the parent node) or from the toolbar, menu. All destination sides must be connected. If the source and destination boundaries are rotated with respect to one other, a transformation is automatically performed, so that corresponding displacement components are connected.

The software automatically identifies the boundaries as either source boundaries or destination boundaries.

	This works fine for simple geometries such as opposing parallel boundaries. In other cases add a Destination Selection subnode to manually specify the destination boundaries. By default it contains the selection that COMSOL Multiphysics has identified. In cases where each periodic boundary is split into several boundaries within the geometry, it can be necessary to apply separate periodic conditions to each pair of geometry boundaries.

By default, there is no periodic condition is active in any of the directions or the electric potential. Select one or more of the , , , or check boxes to activate a periodic condition for the displacements in the x-, y-, and z-directions or for the electric potential (depending on the number of dimensions of the model, some of these options are not available).