# having trouble understanding the Flow Direction option in periodic boundary

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 March 18, 2016, 14:45 having trouble understanding the Flow Direction option in periodic boundary #1 Member     amirhossein Join Date: Jul 2014 Location: iran Posts: 78 Rep Power: 5 Hi can any one help me on "Flow Direction" option in periodic boundary condition ? i didn't understand what is it and how set it thanks

March 19, 2016, 10:27
#2
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amirhossein
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Quote:
 Originally Posted by AHF Hi can any one help me on "Flow Direction" option in periodic boundary condition ? i didn't understand what is it and how set it thanks
any help ?

 March 19, 2016, 10:38 #3 Super Moderator   Sijal Join Date: Mar 2009 Location: Islamabad Posts: 4,352 Blog Entries: 6 Rep Power: 45 what do you mean by flow direction?

March 19, 2016, 11:42
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Aja
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Quote:
 Originally Posted by AHF Hi can any one help me on "Flow Direction" option in periodic boundary condition ? i didn't understand what is it and how set it thanks
I am simulating a turbine and I have Rotational periodic conditions. Here, I think that ""Flow Direction" should be set based on right hand rule.

 March 19, 2016, 12:36 #5 Super Moderator   Sijal Join Date: Mar 2009 Location: Islamabad Posts: 4,352 Blog Entries: 6 Rep Power: 45 things are confusing here. You are saying periodic boundary conditions and at the same time you are saying flow direction.!!!!

March 19, 2016, 12:46
#6
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Aja
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Quote:
 Originally Posted by Far things are confusing here. You are saying periodic boundary conditions and at the same time you are saying flow direction.!!!!

 March 19, 2016, 12:48 #7 Super Moderator   Sijal Join Date: Mar 2009 Location: Islamabad Posts: 4,352 Blog Entries: 6 Rep Power: 45 what type of flow problem you are solving?? It is very much clear. It is direction in which you have pressure gradient. And it has nothing to do with right hand rule... !!! And are you sure that you need this boundary condition?

March 19, 2016, 13:15
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Aja
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Quote:
 Originally Posted by Far what type of flow problem you are solving?? It is very much clear. It is direction in which you have pressure gradient. And it has nothing to do with right hand rule... !!! And are you sure that you need this boundary condition?
What is your exact meaning of "It is direction in which you have pressure gradient."?

My static pressure contour is as follows:

According to above explanations, how do I set this direction?

Last edited by aja1345; March 21, 2016 at 01:23.

 March 19, 2016, 23:20 #9 Super Moderator   Sijal Join Date: Mar 2009 Location: Islamabad Posts: 4,352 Blog Entries: 6 Rep Power: 45 do not make any settings for this boundary. aja1345 likes this.

March 19, 2016, 23:56
#10
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Aja
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Quote:
 Originally Posted by Far do not make any settings for this boundary.
Why?

Can you explain more about that?

Thanks

 March 20, 2016, 06:01 #11 Super Moderator   Sijal Join Date: Mar 2009 Location: Islamabad Posts: 4,352 Blog Entries: 6 Rep Power: 45 these settings for some special problems. They are not for the case you are simulating. So just leave these settings on default... aja1345 likes this.

March 20, 2016, 11:25
#12
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amirhossein
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i will be thankful if any body can help me

this is my problem as seen in the picture attacked

rear and front wall are periodic and also this trapezoidal enclosure is incline. ( gamma angle in picture)
i set rear and front as periodic without any special setting . that is enough ?
or i should change flow direction. please attention that trapezoidal enclosure isn't flat and it is incline

thanks
Attached Images
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March 20, 2016, 11:47
#13
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Sijal
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Quote:
 Originally Posted by AHF i will be thankful if any body can help me this is my problem as seen in the picture attacked rear and front wall are periodic and also this trapezoidal enclosure is incline. ( gamma angle in picture) i set rear and front as periodic without any special setting . that is enough ? or i should change flow direction. please attention that trapezoidal enclosure isn't flat and it is incline thanks

March 20, 2016, 14:22
#14
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amirhossein
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Quote:
i myself create this threat

can you help me

 March 20, 2016, 15:06 #15 Super Moderator   Sijal Join Date: Mar 2009 Location: Islamabad Posts: 4,352 Blog Entries: 6 Rep Power: 45 flow direction is used when you have pressure gradient in some direction. for example if you have long pipe and you want to model just a some finite length. So at inlet and outlet, you just put the periodic conditions and provide direction and pressure gradient. So if pipe length is in x direction then you put direction as 1 0 0

March 22, 2016, 04:18
#16
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amirhossein
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Quote:
 Originally Posted by Far flow direction is used when you have pressure gradient in some direction. for example if you have long pipe and you want to model just a some finite length. So at inlet and outlet, you just put the periodic conditions and provide direction and pressure gradient. So if pipe length is in x direction then you put direction as 1 0 0
so , if i have periodic condition without pressure gradient , its unnecessary to define flow direction ?

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