KR116: How to Repair Rotationally Periodic Zones in FLUENT?
For cases with periodic boundary conditions, the minimum, maximum, average, and prescribed periodic angles are computed and reported when you perform Grid /Check. Many times the reported average angle is incorrect and could lead to convergence issues if not rectified.
Suppose you have a periodic boundary zone (zone ID = 3) with periodic angle of 180 and for some reason during Grid/Check, FLUENT reports the following:(check the image)
Note that the average angle reported is -171.0 which is significantly off from the correct value of 180 deg. To correct this you will use repair-periodic.
Now if you perform Grid/Check to see the corrected rotation angle you will see the following:(check the image)
When you answer "no" to the input "Repair rotational periodic angles?` FLUENT puts you into the pre-6.3 mode where you can specify an angle to repair the periodic. This will try to move the nodes to fix the problem. It may also end up ruining the mesh if the angle disparity is too large (i.e. node movement > cell size). If you answer "yes" it will merely ensure that all periodic angles have the same sign.