How can I used cyclic BC in icoFoam?

sai · October 16, 2009, 17:56

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

santos · October 17, 2009, 05:58

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

alberto · October 17, 2009, 17:25

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,

milleniumrider · November 12, 2009, 10:14

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

alberto · November 12, 2009, 21:54

Quote:

Originally Posted by milleniumrider

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

Hi Vasu,

I meant that if you use cyclic boundary conditions in a pipe with icoFOAM, assuming you give an initial non-zero 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,

milleniumrider · November 13, 2009, 06:33

[QUOTE=alberto;236071]Hi Vasu,

I meant that if you use cyclic boundary conditions in a pipe with icoFOAM, assuming you give an initial non-zero 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

cmh · July 4, 2013, 06:46

Quote:

Originally Posted by alberto

Hi Vasu,

I meant that if you use cyclic boundary conditions in a pipe with icoFOAM, assuming you give an initial non-zero 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,

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

Alawiz · January 17, 2018, 19:56

Hello

I know this is very old thread but it is exactly the same problem I have.

I have added the Ubar line in transportProperties just the same as done in channel395 tutorial and also copied the fvOptions file into my constant folder. However, I am still getting the wrong simulation. Velocity is still decreasing with time and I am getting very low and unreasonable values for it.

Any idea about what have I missed probably?

Thanks

tiam · January 18, 2018, 14:29

Ubar in transportProperties is not needed. You set it in the fvOption instead.

October 16, 2009, 17:56	How can I used cyclic BC in icoFoam?	#1
sai New Member Join Date: Oct 2009 Posts: 1 Rep Power: 0	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, 17:25		#3
alberto Senior Member Alberto Passalacqua Join Date: Mar 2009 Location: Ames, Iowa, United States Posts: 1,912 Rep Power: 36	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, __________________ Alberto Passalacqua GeekoCFD - A free distribution based on openSUSE 64 bit with CFD tools, including OpenFOAM. Available as in both physical and virtual formats (current status: http://albertopassalacqua.com/?p=1541) OpenQBMM - An open-source implementation of quadrature-based 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
milleniumrider New Member Vasu Join Date: Oct 2009 Posts: 17 Rep Power: 17	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

January 17, 2018, 19:56	Cyclic BC and Ubar with IcoFoam	#8
Alawiz New Member Join Date: Dec 2017 Posts: 1 Rep Power: 0	Hello I know this is very old thread but it is exactly the same problem I have. I have added the Ubar line in transportProperties just the same as done in channel395 tutorial and also copied the fvOptions file into my constant folder. However, I am still getting the wrong simulation. Velocity is still decreasing with time and I am getting very low and unreasonable values for it. Any idea about what have I missed probably? Thanks

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October 17, 2009, 05:58		#2
santos Senior Member Jose Luis Santos Join Date: Mar 2009 Location: Portugal Posts: 215 Rep Power: 18	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

November 13, 2009, 06:33		#6
milleniumrider New Member Vasu Join Date: Oct 2009 Posts: 17 Rep Power: 17	[QUOTE=alberto;236071]Hi Vasu, I meant that if you use cyclic boundary conditions in a pipe with icoFOAM, assuming you give an initial non-zero 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

January 18, 2018, 14:29		#9
tiam Senior Member Timofey Mukha Join Date: Mar 2012 Location: Stockholm, Sweden Posts: 119 Rep Power: 14	Ubar in transportProperties is not needed. You set it in the fvOption instead.