# Centrifugal Force¶

This boundary conditions is used to apply the forces that act on a structure when it rotates around a fixed axis. The axis itself has to be fixed, but the rotational speed is allowed to vary with time (or frequency for a harmonic analysis). The user has to specify a volume on which the force acts as well as the rotational speed (in radians per second) and the axis of rotation.

## Rotational speed¶

The rotational speed can be either constant, or a time-dependent (or frequency-dependent respectively). The variable speed has to be given by a function or a table.

## Rotational axis¶

The rotational axis is defined by its direction and a point on the axis.

### Point on axis¶

The user has to define an arbitrary point on the axis of rotation in the global coordinate system of the mesh.

### Axis direction¶

The direction of the rotational axis is defined by three directional values in the global coordinate system. This direction vector doesn’t need to have unit length.