# [ICEM] Setting Periodic Boundary Conditions

 Register Blogs Members List Search Today's Posts Mark Forums Read

January 27, 2012, 11:04
Setting Periodic Boundary Conditions
#1
New Member

Arjun
Join Date: Jan 2012
Posts: 4
Rep Power: 14
Hi I am pretty new to ICEM CFD and need you help. I would like to set periodic boundaries on the sides of this simple geometry.

[IMG]file:///tmp/moz-screenshot.png[/IMG]
Could anyone tell me how to do it? I tried the following.

Went into Mesh --> Global Mesh Setup -----> Global Mesh Parameters ----> Setup periodicity ----------> Rotational Periodicity -------> Rotational Axis ---- User Defined --->

Base : 0 0 0 ( I did not understand its physical meaning so set to origin)
Axis: 1 0 0 (I needed the object to be rotated about x-axis)
Angle: 90 ( as the sector makes 90 degrees)

Is this the right way to do ? I also tried the edit block periodic vertices but could not really understand how to use it. SO could anyone tell me how to set periodic faces. Thanks
Attached Images
 7.jpg (47.9 KB, 425 views)

 January 27, 2012, 15:10 #2 Super Moderator   Sijal Join Date: Mar 2009 Location: Islamabad Posts: 4,553 Blog Entries: 6 Rep Power: 54 Check this

 January 29, 2012, 22:37 #3 Super Moderator   Sijal Join Date: Mar 2009 Location: Islamabad Posts: 4,553 Blog Entries: 6 Rep Power: 54 This is the what I found from the ICEM 10 tutorial guide. 3.15. Periodicity Periodic definition may be applied to the model in Hexa. The Periodic nodes function, which is found under Blocking > Periodic nodes, plays a key role in properly analyzing rotating machinery applications, for example. Typically, the user will model only a section of the rotating machinery, as well as implement symmetry, in order to minimize the model size. By specifying a periodic relationship between the inflow and outflow boundaries, the particular specification may be applied to the model -- flow characteristics entering a boundary must be identical to the flow characteristics leaving a boundary. 3.15.1. Applying the Periodic Relationship The periodic relationship is applied to block faces and ensures that a node on the first boundary have two identical coordinates to the corresponding node on the second boundary. The user is prompted to select corresponding vertices on the two faces in sequence. When all vertices on both flow boundaries have been selected, a full periodic relationship between the boundaries has been generated. I am also confused in term Base.

January 30, 2012, 07:39
#4
New Member

Arjun
Join Date: Jan 2012
Posts: 4
Rep Power: 14
Dear Far, thanks a lot for both of your kind replies. I still could not figure out the order to set the periodicity. I have attached this very basic setup of the case. I have already set the periodic condition in the global mesh set up. Then I went into the vertex periodicity in the blocking. I also activated the solid blocking and show periodic face in the blocking section of the model tree to understand. But after every time I finishing selecting the vertices, I get the periodic faces weirdly highlighted. I tried seclecting the vertices in different ways but still wrong periodic faces. Can you please tell me the sequence to set up the periodic boundary condition. Could you please let me know how to do this periodicity?
Attached Files
 Simple_periodic.tar.gz (14.8 KB, 85 views)

 January 30, 2012, 07:49 #5 New Member   Arjun Join Date: Jan 2012 Posts: 4 Rep Power: 14 Far ! I have found the answer. I went into vector defined in Global parameters and then selected two points in the axis of rotation. Then I went into vertices association and selected one node on one periodic face and corresponding node in the other periodic face ... bingo ! I got the periodic condition on the periodic faces. Thanks

 January 30, 2012, 09:47 #6 Super Moderator   Sijal Join Date: Mar 2009 Location: Islamabad Posts: 4,553 Blog Entries: 6 Rep Power: 54 Hi Arjun, I am unable to understand that what is the purpose of all this in ICEM. If you just export the mesh with periodic boundaries as wall, you can still make them periodic in Fluent.

January 30, 2012, 10:06
#7
Super Moderator

Sijal
Join Date: Mar 2009
Posts: 4,553
Blog Entries: 6
Rep Power: 54
Quote:
 Far ! I have found the answer. I went into vector defined in Global parameters and then selected two points in the axis of rotation. Then I went into vertices association and selected one node on one periodic face and corresponding node in the other periodic face ... bingo ! I got the periodic condition on the periodic faces. Thanks
I dont think so you could get periodicity in this way!!!!

 January 30, 2012, 10:59 #8 New Member   Arjun Join Date: Jan 2012 Posts: 4 Rep Power: 14 Dear Far, Do you know the correct way to do it ? I am not sure whether its the right way but I got periodic condition. It will be helpful if you could say. And answering to your question, periodic conditions ensures that there is a one to one r-theta match in the periodic nodes. Not all solvers unlike Fluent are capable of dealing with periodic meshes where a strict one to one matching does not occur. Hence the strict periodicity needs to be ensured in meshing before sending into solver. aerosaravanan likes this.

 January 30, 2012, 11:50 #9 Super Moderator   Sijal Join Date: Mar 2009 Location: Islamabad Posts: 4,553 Blog Entries: 6 Rep Power: 54 What I want to say is that, any software should be intelligent enough to understand the basic requirements. For example 1. if you increase the sector from 90 to 120, you again need to copy the geometry to those angles and and again re-associate the edges, vertices and faces. This should be handled automatically in code. 2. Some times it is not good idea in turbo machinery to model the strict plain surface in periodic boundaries, instead they should be floated in a way to facilitate the blocking. For example some times it is better to align the blade blocking near the low periodic and some times to high periodic depending on the blade angles and curvature. 3. Once you have defined the two surfaces as periodic then they should show periodic condition in the boundary condition panel (in output tab), instead asking user to define it. With the help of GGI (general grid interfaces), you dont even need the periodicity in mesh at all. You can make two dissimilar face meshes periodic by use of GGI method. Available in both Fluent and CFX. Last edited by Far; January 30, 2012 at 12:08.

January 30, 2012, 11:55
#10
Super Moderator

Sijal
Join Date: Mar 2009
Posts: 4,553
Blog Entries: 6
Rep Power: 54
Quote:
 Dear Far, Do you know the correct way to do it ? I am not sure whether its the right way but I got periodic condition. It will be helpful if you could say.
I also use similar method, I go to global mesh settings and set the required angle and axis. Since currently I am working on bladegen and get the turbine or compressor file from there, I normally find that these conditions are pre defined.
But I have no idea about the base point that how is defined and what is physical significance.
Then I go to Block---> edit block ---> Periodic vertices and make the vertices periodic and when I display the vertex with periodicity on, I can see the red arrow pointing to each other.

 February 6, 2012, 12:58 #11 Super Moderator   Sijal Join Date: Mar 2009 Location: Islamabad Posts: 4,553 Blog Entries: 6 Rep Power: 54 I guess that base point is important in 2-D vertical wind turbine periodic setup, where you pivot the whole mesh. Vertical wind turbine

 April 14, 2015, 03:05 how to make periodic boundary condition in a cube #12 New Member   masoud karami Join Date: Apr 2015 Posts: 1 Rep Power: 0 Dear friends I want to make periodic bondary conditions in the left and right side of a cube,and I dont know how can I do that. I wanna you to help me,I konw it is very simple but I am amateur in gambit

 April 14, 2015, 05:12 #13 Senior Member   Javi Join Date: Jan 2013 Posts: 276 Rep Power: 16 Hi Masoud! Just try to check out the second reply on this thread posted by FAR. There, you can find explanation and videos about how to do this in ICEM CFD! Hope it helps

 March 10, 2017, 02:33 #14 New Member   Abhijeet Join Date: Mar 2017 Posts: 2 Rep Power: 0 FAR Sir, Can we do the same thing with interior surfaces also i.e just exporting the mesh with periodic boundaries as wall and then changing them to interior in fluent?

 March 10, 2017, 14:10 #15 Super Moderator   Sijal Join Date: Mar 2009 Location: Islamabad Posts: 4,553 Blog Entries: 6 Rep Power: 54 this can be done

 March 14, 2017, 03:34 #16 New Member   Abhijeet Join Date: Mar 2017 Posts: 2 Rep Power: 0 Thankyou FAR sir for your reply. Sir, I am trying to mesh a geometry using ICEM CFD but i am facing a lot of problems such as multiple edges etc can you please give me your email id so that i can share the geometry with you and find out possible solutions to my problems.