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arash June 20, 2008 18:50

Periodic boundary condition in 2 directions
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

Phil June 21, 2008 13:18

Re: Periodic boundary condition in 2 directions
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

arash June 22, 2008 06:13

Re: Periodic boundary condition in 2 directions
any idea?

arash June 22, 2008 06:18

Re: Periodic boundary condition in 2 directions
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.

Phil June 22, 2008 08:04

Re: Periodic boundary condition in 2 directions
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?

Paolo Lampitella June 23, 2008 04:37

Re: Periodic boundary condition in 2 directions
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

arash June 24, 2008 09:29

Re: Periodic boundary condition in 2 directions
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.

Paolo Lampitella June 24, 2008 13:10

Re: Periodic boundary condition in 2 directions
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

ccy329 August 6, 2015 03:31


I was wondering if anyone knows how to solve this problem as I encounter the same problem.

I would like to set translational periodic boundary conditions in the streamwise direction with specified flow rate as well as in the spanwise direction with zero pressure gradient. If I set the periodic conditions for the streamwise direction with a mass flow rate, it sets the same periodic conditions to the other periodic boundary which in this case, the spanwise direction.

How do I define two different periodic boundary conditions separately in Fluent?

I am relatively new to Fluent. Any advise will be greatly appreciated.

LuckyTran August 7, 2015 13:05

You need to specify the periodic boundary pair with the zero pressure gradient as an interface.

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