10.4 Mesh Setup for a Single Rotating Reference Frame

It is important to remember the following coordinate-system constraints when you are setting up a problem involving a rotating reference frame:

• For 2D problems, the axis of rotation must be parallel to the $z$ axis.

• For 2D axisymmetric problems, the axis of rotation must be the $x$ axis.

• For 3D geometries, you should generate the mesh with a specific rotational axis in mind for the rotating cell zone. Usually it is convenient to use the $x$, $y$, or $z$ axis, but ANSYS FLUENT can accommodate arbitrary rotational axes.

With 3D geometries, it is also important to note that if you wish to include walls which have zero velocity in the stationary frame, these walls must be a surface of revolution with respect to the axis of rotation. If the stationary walls are not surfaces of revolution, you must encapsulate the rotating parts with interface boundaries, thereby breaking your model up into multiple zones, and use either the MRF or mixing plane models for steady state solutions (see Sections  10.3.1 and 10.3.2), or the sliding mesh model for unsteady interaction (see Chapter  11).