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The Continuity, Antiperiodicity, and User defined periodic conditions directly prescribe relations between displacements and can be used for any type of study.
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The Floquet periodicity can be used for frequency domain problems with a spatial periodicity of the geometry and solution. The structure is typically a unit cell of a repetitive structure.
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The Cyclic symmetry is a special case of a Floquet condition, intended for structures that consist of a number of sectors that are identical when rotated around a common axis, like a blade in a turbine.
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The software usually automatically identifies the boundaries as either source boundaries or destination boundaries, as indicated in the selection list. This works fine for cases like opposing parallel boundaries. In other cases, right-click Periodic Condition and select Manual Destination Selection to control the destination. By default it contains the selection that COMSOL Multiphysics identifies.
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For Continuity the displacements on the destination are set equal to the displacements on the source;
 . If the source and destination boundaries are rotated with respect to each other, a transformation is automatically performed, so that corresponding displacement components are connected. |
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For Antiperiodicity the displacements on the destination are set equal to the displacements on the source with the sign reversed;
 . If the source and destination boundaries are rotated with respect to each other, a transformation is automatically performed, so that corresponding displacement components are connected. |
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For Floquet periodicity enter a k-vector for Floquet periodicity kF. This is the wave number vector for the excitation.
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For Cyclic symmetry choose how to define the sector angle that the geometry represents using Sector angle. If Automatic is selected, the program attempts to find out how many full repetitions of the geometry there will be on a full revolution. If User defined is selected, enter a value for the sector angle θS. In both cases, also enter an Azimuthal mode number for the mode to be studied. It can vary from 0 to N/2, where N is the total number of sectors on a full revolution.
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For User defined select the check box for any of the displacement components as needed. Then for each selection, choose the Type of periodicity — Continuity or Antiperiodicity. Each selected displacement component will be connected by ui(xd) = ui(xs) or ui(xd) = −ui(xs). If the source and destination boundaries are rotated with respect to each other, a transformation is automatically performed, so that corresponding displacement components are connected.
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) and select Advanced Physics Options in the Show More Options dialog box.
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In the COMSOL Multiphysics Reference Manual:
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) and select Advanced Physics Options in the Show More Options dialog box. For more information about these sections, see Excluded Surfaces, Excluded Edges, and Excluded Points in the COMSOL Multiphysics Reference Manual.
) 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.
) and select Advanced Physics Options in the Show More Options dialog box. For information about the Mapping Between Source and Destination section, see Mapping Between Source and Destination in the COMSOL Multiphysics Reference Manual.
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Vibrations of an Impeller: Application Library path Structural_Mechanics_Module/Dynamics_and_Vibration/impeller
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