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6.8.4 Creating Periodic Zones

FLUENT allows you to set up periodic boundaries using either conformal or non-conformal periodic zones. You can assign periodicity to your grid by coupling a pair of face zones. If the two zones have identical node and face distributions, you can create a conformal periodic zone. If the two zones are not identical at the boundaries within a specified tolerance, then you can create a non-conformal periodic zone. (See Section  6.4 for more information about non-conformal grids.)


Remember to save a new case file (and a data file, if data exist) after creating or slitting a periodic boundary.

Creating Conformal Periodic Zones

To create conformal periodic boundaries, you will use the make-periodic text command.

grid $\rightarrow$ modify-zones $\rightarrow$ make-periodic

You will need to specify the two face zones that will comprise the periodic pair (you can enter their full names or just their IDs), and indicate whether they are rotationally or translationally periodic. The order in which you specify the periodic zone and its matching shadow zone is not significant.

/grid/modify-zones> mp

Periodic zone [()] 1

Shadow zone [()] 4

Rotational periodic? (if no, translational) [yes] n

Create periodic zones? [yes] yes

  computed translation deltas: -2.000000 -2.000000 
  all 10 faces matched for zones 1 and 4.

  zone 4 deleted
 Created periodic zones.

When you create a conformal periodic boundary, the solver will check to see if the faces on the selected zones "match'' (i.e., whether or not the nodes on corresponding faces are coincident). The matching tolerance for a face is a fraction of the minimum edge length of the face. If the periodic boundary creation fails, you can change the matching tolerance using the matching-tolerance command, but it should not exceed 0.5 or you may match up the periodic zones incorrectly and corrupt the grid.

grid $\rightarrow$ modify-zones $\rightarrow$ matching-tolerance

Creating Non-Conformal Periodic Zones

To create non-conformal periodic boundaries, you need to change the non-conformal periodic zones to interface zones. You will then need to set up the origin as well as the axes of the adjacent cell zone. For example, if interface-15 and interface-2 are the two non-conformal periodic zones, the non-conformal periodic boundaries are set up using the make-periodic command in the define/grid-interfaces text menu.

define $\rightarrow$ grid-interfaces $\rightarrow$ make-periodic

For example:

/define/grid-interfaces> make-periodic

Periodic zone [()] interface-15

Shadow zone [()] interface-2

Rotational periodic? (if no, translational) [yes] yes

Rotation angle (deg) [0] 40.0

Create periodic zone? [yes] yes

grid-interface name [] fan-periodic


If non-conformal periodics are used, they should not be intersected by any other non-conformal interfaces. Note that the created non-conformal periodic zones cannot be used with 3-D sliding mesh cases.

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© Fluent Inc. 2006-09-20