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Periodic boundary condition in 2 directions

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Old   June 20, 2008, 18:50
Default Periodic boundary condition in 2 directions
  #1
arash
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Hi! can anyone anwser me please? i am modeling a rotating channel and i have to define periodic boundary condition in two directions ,one in x and another in z direction , the channel is rotaing around y axes, i can make the 2 different periodic zones , but how can i set the periodic conditions for the both directions? because at the menu Defin/periodic condition i can just set the condition for one direction. thanks
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Old   June 21, 2008, 13:18
Default Re: Periodic boundary condition in 2 directions
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Phil
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You should make the 2 seperate periodic boundaries first in the pre-processor, then define each seperate in fluent. You don't supply a direction in fluent just whether it is rotational or translational.

From what I gather your x is rotational, and your z translational.

Hope this helps Phil
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Old   June 22, 2008, 06:13
Default Re: Periodic boundary condition in 2 directions
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arash
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any idea?
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Old   June 22, 2008, 06:18
Default Re: Periodic boundary condition in 2 directions
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arash
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tnx ,but my problem is that , i should give a pressure gradiant in x direction ,but zero pressure gradiant in z direction , i can make the two periodic zones , but in periodic condition theres is nothing to choose one of this zones !and i think when i give a pressure gradiant it will assigned to both zones.
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Old   June 22, 2008, 08:04
Default Re: Periodic boundary condition in 2 directions
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Phil
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To be honest I'm unsure what you mean by pressure gradient but it sounds like maybe one of them should be symmetry instead of periodic?
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Old   June 23, 2008, 04:37
Default Re: Periodic boundary condition in 2 directions
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Paolo Lampitella
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if you carefully check the panel periodic boundary conditions under define (after you defined the two couples of periodic boundaries) you will see a blank for the specification of the pressure gradient and something (i don't remember actually) for specifying the direction of the pressure gradient

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Old   June 24, 2008, 09:29
Default Re: Periodic boundary condition in 2 directions
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arash
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thanks for your reply , but as i have mentioned before i have to define two seperate periodic boundary conditions one with pressure gradient and another with zero pressure gradient, but in pannel which you mentioned there is no option for choosing the appropriate boundary condition zone ,then i think when i give a pressure gradient it will be set for both periodic zones which is not correct.
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Old   June 24, 2008, 13:10
Default Re: Periodic boundary condition in 2 directions
  #8
Paolo Lampitella
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sorry, i did not understood (my poor english) very well, but maybe could works also in your case.

For example, in my turbulent channel flow i have the flow along the positive x axis (streamwise) and the z axis is the transverse direction (the y axis is perpendicular to the walls). If i want the flow goes along the x axis i just put this as direction. The faces perpendicular to the z axis will have just the same gradient that will be parallel to those faces.

However this works just in non-rotating channel with the two couples of sides being perpendicular to each other.

If your domain is a rectangular channel you could apply a source term to simulate the rotation and use this method to apply periodic boundary conditions.

Hope this helps
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