11.2.1 Requirements and Constraints

Before beginning the problem setup in ANSYS FLUENT, be sure that the mesh you have created meets the following requirements:

• A different cell zone exists for each portion of the domain that is sliding at a different speed.

• The mesh interface must be situated such that there is no motion normal to it.

• The mesh interface can be any shape (including a non-planar surface, in 3D), provided that the two interface boundaries are based on the same geometry. If there are sharp features in the mesh (e.g., 90-degree angles), it is especially important that both sides of the interface closely follow that feature.

• If you create a single mesh with multiple cell zones, you must be sure that each cell zone has a distinct face zone on the sliding boundary. The face zones for two adjacent cell zones will have the same position and shape, but one will correspond to one cell zone and one to the other. (Note that it is also possible to create a separate mesh file for each of the cell zones, and then merge them as described in Section  6.3.15.)

• If you are modeling a rotor/stator geometry using periodicity, the periodic angle of the mesh around the rotor blade(s) must be the same as that of the mesh around the stationary vane(s).

• All periodic zones must be correctly oriented (either rotational or translational) before you create the mesh interface.

• Note the following limitations if you want to use the periodic repeats option as part of the mesh interface:
  • The edges of the second interface zone must be offset from the corresponding edges of the first interface zone by a uniform amount (either a uniform translational displacement or a uniform rotation angle).

  • Some portion of the two interface zones must overlap (i.e., be spatially coincident).

  • The non-overlapping portions of the interface zones must have identical shape and dimensions at all times during the mesh motion.

  • One pair of conformal periodic zones must be adjacent to each of the interface zones. For example, when you calculate just one channel and blade of a fan, turbine, etc., you must have conformal periodics on either side of the interface threads. This will not work with non-conformal periodics.

    Note that for 3D cases, you cannot have more than one pair of conformal periodic zones adjacent to each of the interface zones.

• You must not have a single sliding mesh interface where part of the interface is made up of a coupled two-sided wall, while another part is not coupled (i.e., the normal interface treatment). In such cases, you must break the interface up into two interfaces: one that is a coupled interface, and the other that is a standard fluid-fluid interface. See Section  6.4.4 for information about creating coupled interfaces.

For details about these restrictions and general information about how the sliding mesh model works in ANSYS FLUENT, see this section in the separate Theory Guide.