Periodic Boundary Conditions
The Wave Optics Module has a dedicated Periodic Condition. The periodic condition can identify simple mappings on plane source and destination boundaries of equal shape. The destination can also be rotated with respect to the source. There are three types of periodic conditions available (only the first two for transient analysis):
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Continuity — The tangential components of the solution variables are equal on the source and destination.
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Antiperiodicity — The tangential components have opposite signs.
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Floquet periodicity — There is a phase shift between the tangential components. The phase shift is determined by a wave vector and the distance between the source and destination. Floquet periodicity is typically used for models involving plane waves interacting with periodic structures.
Periodic boundary conditions must have compatible meshes. This can be done automatically by enabling Physics-controlled mesh in the Sequence Type section in the settings for the mesh or by manually setting up the correct mesh sequence
If more advanced periodic boundary conditions are required, for example, when there is a known rotation of the polarization from one boundary to another, see Nonlocal Couplings and Coupling Operators in the COMSOL Multiphysics Reference Manual for tools to define more general mappings between boundaries.
To learn how to use the Copy Mesh feature to ensure that the mesh on the destination boundary is identical to that on the source boundary, see Band-Gap Analysis of a Photonic Crystal: Application Library path Wave_Optics_Module/Gratings_and_Metamaterials/bandgap_photonic_crystal.
For an example of how to use the Physics-controlled mesh, see Fresnel Equations: Application Library path Wave_Optics_Module/Verification_Examples/fresnel_equations.
In the COMSOL Multiphysics Reference Manual:
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Periodic Condition
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Periodic Boundary Conditions