The Periodic Condition can be used to remove particles that make contact with a source boundary and reinsert them at some other boundary, the destination. The boundaries must be planar and cannot be curved. At least two boundaries must be selected.
This section is available for specifying the destination boundaries, if needed, when the Manual Destination Selection option is selected in the context menu for the
Periodic Condition node. You can only select destination boundaries from the union of all source and destination boundaries.
If Continuity is selected, the particle velocity at the destination boundary is equal to the velocity at the source boundary.
If User defined is selected, enter values or expressions for the components of the
Reinitialized particle velocity vr (SI unit: m/s). The default is zero. Expressions for the reinitialized particle velocity are evaluated at the source boundary, not the destination; for example, expressions in terms of tangential and normal vector components will use the directions tangent or normal to the source boundary. If the velocity is such that the particle will immediately leave the modeling domain through the destination boundary, the particle will instead disappear, to prevent the particle from being subjected to an arbitrarily large number of successive boundary interactions.
In other words, if a particle were to get stuck in an infinite loop between the source and destination boundaries in a Periodic Condition, the particle would instead go through a large but finite number of wall interactions, then disappear if the interaction is still not resolved.
To display this section, click the Show More Options button (
) and select
Advanced Physics Options in the
Show More Options dialog box. For information about the
Orientation of Source section, see
Orientation of Source and Destination in the
COMSOL Multiphysics Reference Manual.
This section appears if the setting for Transform to intermediate map in the
Orientation of Source section is changed from the default value,
Automatic, and
Advanced Physics Options is selected in the
Show More Options dialog box. For information about the
Orientation of Destination section, see
Orientation of Source and Destination in the
COMSOL Multiphysics Reference Manual.