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October 16, 2009, 16:56 
How can I used cyclic BC in icoFoam?

#1 
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Hi, I'm trying to simulate a laminar flow trough a pipe with icoFoam using cyclic BC on the inlet and outlet of the tube. I want to impose the pressure gradient between the faces but I can't. It seems like the cyclic condition doesn't accept another condition.
I would like to find an way to impose the pressure gradient and mantain the cyclic condition between the inlet and outlet of the tube. Thanks 

October 17, 2009, 04:58 

#2 
Senior Member

Hi,
I dont think icoFoam allows the use of cyclics. You can use instead channelFoam and switch LESModel to laminar in LESProperties. Regards, Jose Santos 

October 17, 2009, 16:25 

#3 
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Alberto Passalacqua
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icoFoam allows cyclic BC's to be used, but it has not mechanism to impose a fixed pressure gradient.
To do that you need to add your constant pressure gradient at the momentum equation. channelFoam imposes a fixed flow rate. Best,
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Alberto Passalacqua GeekoCFD  A free distribution based on openSUSE 64 bit with CFD tools, including OpenFOAM. Available as in both physical and virtual formats. OpenQBMM  An opensource implementation of quadraturebased moment methods. To obtain more accurate answers, please specify the version of OpenFOAM you are using. 

November 12, 2009, 10:14 
hi i'd like some more information on what you suggested

#4 
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Vasu
Join Date: Oct 2009
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Hi Alberto,
Can you elaborate a little on what you said. Constant pressure gradient, in icoFoam? I'm sorry if this is an extremely basic question, I've just started CFD and am still grappling my way through. Any help or explanation would be much appreciated. Thanks, Vasu 

November 12, 2009, 21:54 

#5  
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Alberto Passalacqua
Join Date: Mar 2009
Location: Ames, Iowa, United States
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Quote:
I meant that if you use cyclic boundary conditions in a pipe with icoFOAM, assuming you give an initial nonzero velocity to the flow, you will notice, if you use the code as is, that the fluid slows down in time due to the effect of the wall. If you want to compute a flow with a constant mean mass flow rate or a constant pressure gradient between inlet and outlet you need to change the code. If you want to impose a constant pressure gradient, all you have to do is adding it to the momentum equation. If you want to impose a constant mass flow rate, you need to do something similar to what is done in channelFoam. Best,
__________________
Alberto Passalacqua GeekoCFD  A free distribution based on openSUSE 64 bit with CFD tools, including OpenFOAM. Available as in both physical and virtual formats. OpenQBMM  An opensource implementation of quadraturebased moment methods. To obtain more accurate answers, please specify the version of OpenFOAM you are using. 

November 13, 2009, 06:33 

#6 
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Vasu
Join Date: Oct 2009
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[QUOTE=alberto;236071]Hi Vasu,
I meant that if you use cyclic boundary conditions in a pipe with icoFOAM, assuming you give an initial nonzero velocity to the flow, you will notice, if you use the code as is, that the fluid slows down in time due to the effect of the wall. Yep thankfully thats what happens. If you want to compute a flow with a constant mean mass flow rate or a constant pressure gradient between inlet and outlet you need to change the code. If you want to impose a constant pressure gradient, all you have to do is adding it to the momentum equation. If you want to impose a constant mass flow rate, you need to do something similar to what is done in channelFoam. Ok I think I understand. I've been comparing it with the channelFoam case to try to understand better. I'll give it a shot and see how it goes. Thanks for the help! Cheers, Vasu 

July 4, 2013, 05:46 

#7  
New Member
Chiranth Hegde
Join Date: Jun 2013
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Quote:
HI Alberto, Newbie alert. Anyhow how do I modify the code in Icofoam such that i can provide the pressure gradient at the inlet and the outlet to calculate the velocity? Regards 

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