Discretization Type of Periodic Interface

newbie384 · March 3, 2014, 15:20

I checked my output file and I realized that the discretization type of periodic interface is 1:1. However, one of the periodic interface has GGI discretization type even though the interface mode is set to rotational periodicity. (See attached picture)

Is there something wrong here? or it is just the result of some automatic procedures by CFX?

ghorrocks · March 3, 2014, 16:19

If the mesh does not match perfectly (or at least to a pretty tight tolerance) then it cannot use 1:1 and rolls back to GGI. Even a single node misplaced can trigger this. Have a very close look at your mesh interfaces to find the unmatched node.

newbie384 · March 3, 2014, 16:29

Thank you for your quick response. Some of the meshes were created in TurboGrid and some were created in ICEM CFD. There is usually no problem with the periodic interface for the meshes created by TurboGrid. However, I found that sometime there will be problem with periodic interface in CFX, for the mesh created by ICEM CFD, even though I have defined periodic vertices in ICEM CFD and everything looks perfect in ICEM CFD(I looked at periodic association for vertices and faces). Is there anyway to overcome this problem?

ghorrocks · March 3, 2014, 16:40

As I said the problem is the mesh does not match exactly. So you have to match the meshes up and find which node does not align. Then you can move the node to where it is meant to be in ICEM.

newbie384 · March 3, 2014, 22:56

Thank you so much for your advise. I solved the problem by removing the periodic in ICEM CFD. It seems that there will be problem in CFX if we pre-defined periodic in ICEM CFD.

singer1812 · March 4, 2014, 10:50

You need to run the check mesh routine in ICEM. It is under the Edit Mesh tab, and will do a series of checks (this will identify problems that might occur down the line).

One of the checks is periodic. It will do through the nodes on the periodic surfaces and line them up if they are off.

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March 3, 2014, 16:19		#2
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,703 Rep Power: 143	If the mesh does not match perfectly (or at least to a pretty tight tolerance) then it cannot use 1:1 and rolls back to GGI. Even a single node misplaced can trigger this. Have a very close look at your mesh interfaces to find the unmatched node.

March 3, 2014, 16:29		#3
newbie384 Member Join Date: Mar 2013 Posts: 68 Rep Power: 13	Thank you for your quick response. Some of the meshes were created in TurboGrid and some were created in ICEM CFD. There is usually no problem with the periodic interface for the meshes created by TurboGrid. However, I found that sometime there will be problem with periodic interface in CFX, for the mesh created by ICEM CFD, even though I have defined periodic vertices in ICEM CFD and everything looks perfect in ICEM CFD(I looked at periodic association for vertices and faces). Is there anyway to overcome this problem?

March 3, 2014, 16:40		#4
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,703 Rep Power: 143	As I said the problem is the mesh does not match exactly. So you have to match the meshes up and find which node does not align. Then you can move the node to where it is meant to be in ICEM.

March 3, 2014, 22:56		#5
newbie384 Member Join Date: Mar 2013 Posts: 68 Rep Power: 13	Thank you so much for your advise. I solved the problem by removing the periodic in ICEM CFD. It seems that there will be problem in CFX if we pre-defined periodic in ICEM CFD.

March 4, 2014, 10:50		#6
singer1812 Senior Member Edmund Singer P.E. Join Date: Aug 2010 Location: Minneapolis, MN Posts: 511 Rep Power: 20	You need to run the check mesh routine in ICEM. It is under the Edit Mesh tab, and will do a series of checks (this will identify problems that might occur down the line). One of the checks is periodic. It will do through the nodes on the periodic surfaces and line them up if they are off.