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January 27, 2012, 11:04 
Setting Periodic Boundary Conditions

#1 
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Arjun
Join Date: Jan 2012
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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/mozscreenshot.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 xaxis) 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 

January 29, 2012, 22:37 

#3 
Super Moderator

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 
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Arjun
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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?


January 30, 2012, 07:49 

#5 
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Arjun
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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

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

Quote:


January 30, 2012, 10:59 

#8 
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Arjun
Join Date: Jan 2012
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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 rtheta 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. 

January 30, 2012, 11:50 

#9 
Super Moderator

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 reassociate 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

Quote:
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

I guess that base point is important in 2D 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 
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masoud karami
Join Date: Apr 2015
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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 
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Javi
Join Date: Jan 2013
Posts: 276
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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 
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Abhijeet
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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 14, 2017, 03:34 

#16 
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Abhijeet
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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.


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