The Periodic Flow Condition splits its selection into a source group and a destination group. Fluid that leaves the domain through one of the destination boundaries enters the domain through 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 velocity vector is automatically transformed.
A value or expression should be specified for the Pressure difference,
psrc − pdst. This pressure difference can, for example, drive the fully developed flow in a channel.
To set up a periodic boundary condition, both boundaries must be selected in the Periodic Flow Condition node. COMSOL Multiphysics automatically assigns one boundary as the source and the other as the destination. To manually set the destination selection, a
Destination Selection subnode is available from the context menu (by right-clicking the parent node) or from the
Physics toolbar,
Attributes menu. All destination sides must be connected.
) and selecting Advanced Physics Options in the Show More Options dialog box.