Periodic Condition

The node adds a periodic boundary condition that can be used to reduce the model size by using symmetries and periodicities in the geometry and physics interfaces being modeled. This feature works well for cases like opposing parallel boundaries. In other cases, use a subnode to control the destination. By default, it contains the selection that COMSOL Multiphysics identifies.

Periodicity Settings

Select a : (the default), , (Bloch periodicity), or .

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For , also known as Bloch periodicity, enter a kF (SI unit: rad/m) for the , , and coordinates (3D components), the and coordinates (2D axisymmetric components), or and coordinates (2D components).

This condition is used to model infinite periodic structures with nonnormal incident pressure fields or excitations. Use it to model, for example, a large perforated plate with an oblique incident wave with wave vector k (and set kF = k) by only analyzing one hole or one subset of holes that is periodic.

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For select a : (the default) or . For enter a value for θS (SI unit: rad). Enter an m (dimensionless).

This condition is used to model any geometry that has a cyclic periodic structure such as a microphone or a loudspeaker driver. Setting the azimuthal mode number determines what mode is analyzed. The response of the full system to an external excitation is in general a linear combination of many different modes.

In the time domain, both the and the boundary conditions reduce to the continuity condition.


	To optimize the performance of the Floquet periodicity and the Cyclic symmetry conditions, it is recommended that the source and destination meshes are identical. This can be achieved by first meshing the source boundary or edge and then copying the mesh to the destination boundary or edge. When the Periodic Condition stretches across regions with a mix of default material models, PMLs, background pressure fields, or background acoustic fields, it is recommended to add one Periodic Condition for each set of such boundaries.


	The Porous Absorber model uses Floquet periodic boundary conditions to model an infinite porous absorber used for sound proofing. The Application Library path is Acoustics_Module/Building_and_Room_Acoustics/porous_absorber

Constraint Settings

To display this section, select in the dialog box.

Excluded Edges

To display this section, select in the dialog box.

Excluded Points

To display this section, select in the dialog box.

Orientation of Source

To display this section, select in the dialog box.

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See Orientation of Source and Destination in the COMSOL Multiphysics Reference Manual.

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See Excluded Surfaces, Excluded Edges, and Excluded Points in the COMSOL Multiphysics Reference Manual.