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.
No input is required when Compressible flow (Ma<0.3) is selected for
Compressibility under the
Physical Model section for the physics interface. Typically when a periodic boundary condition is used with a compressible flow, the pressure is the same at both boundaries and the flow is driven by a volume force.
This section is available when Incompressible flow is selected for
Compressibility under the
Physical Model section for the physics interface.
The Flow Condition at the boundary is specified through a value or expression for either the
Pressure difference,
, or the
Mass flow,
. The mass flow option ensures a pressure difference is achieved across the source and destination boundaries. 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