# Cyclic Symmetry¶

The **cyclic symmetry** constraint enables to model only a sector of a 360° cyclic periodic
structure and reduces the computation time and memory consumption considerably.
The user defines the center and axis of the cyclic symmetry as well as the sector angle.
The *master* and *slave* surfaces define the cyclic periodicity boundaries.

## Selection of master and slave faces¶

Generally the more refined of the two periodic boundary surfaces should be chosen to be the **slave**.
In the case of a cyclic symmetry this will in the most cases not matter since both faces should be
meshed with nearly the same element sizes.

## Definition of the cyclic symmetry axis and sector angle¶

The user has to define the axis of revolution and the sector angle explicitly.
The **sector angle** has to be given in degrees. Available ranges for the angle are from 0° to 180°
and only values that divide 360° to an integer number are valid.
The axis is defined by the **axis origin** and the **axis direction**.
The Definition of Axis and Angle has to be in accordance with the right hand rule
such that it defines a rotation that maps the slave to the master surface.

For an example see the picture below:

Important remarks:

- All DOFs of the slave nodes will be constrained, adding an additional constraint on those nodes could lead to an overconstrained system.
- This is a
**linear**constraint, so no large rotations or large deformations are allowed in the proximity of cyclic symmetry boundaries. - A cyclic symmetry condition is only valid if geometry
**and**loading conditions are symmetric.