# Boundary condition in outdoor flow

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 July 19, 2013, 05:37 Boundary condition in outdoor flow #1 New Member   zako Join Date: Apr 2012 Posts: 7 Rep Power: 7 Hi Guys, I would like to set up a simulation with no wind flow. which boundary condition is more appropriate. any help is most welcome Regards

 July 21, 2013, 20:34 #2 Senior Member     Mojtaba Amiraslanpour Join Date: Jun 2011 Location: Zanjan, Iran Posts: 291 Rep Power: 9 What do you mean by no wind flow? __________________ Learn OpenFOAM in Persian for free, And ask your questions here. Complex Heat & Flow Simulation Research Group If you can't explain it simply, you don't understand it well enough. "Richard Feynman"

 July 22, 2013, 03:22 #3 New Member   zako Join Date: Apr 2012 Posts: 7 Rep Power: 7 Hi Mojtaba.a, Thanks for your reply. I have a flow field with an inlet and outlet flow But I am interested in investgating a situation in which the inlet velocity is zero. I was wondering what are the boundary condition appropriate for this kind of simulation. I am using simpleFoam with a k and omega tubulence model. kind regards

July 22, 2013, 08:10
#4
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Mojtaba Amiraslanpour
Join Date: Jun 2011
Location: Zanjan, Iran
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Quote:
 Originally Posted by bigzakk Hi Mojtaba.a, Thanks for your reply. I have a flow field with an inlet and outlet flow But I am interested in investgating a situation in which the inlet velocity is zero. I was wondering what are the boundary condition appropriate for this kind of simulation. I am using simpleFoam with a k and omega tubulence model. kind regards
If you have zero inlet velocity, so what is going to move your fluid flow?
looking at your selected solver, you are not going to solve a natural convection problem either.
So what exactly are you going to model?
__________________
Complex Heat & Flow Simulation Research Group
If you can't explain it simply, you don't understand it well enough. "Richard Feynman"

 July 22, 2013, 08:21 #5 New Member   zako Join Date: Apr 2012 Posts: 7 Rep Power: 7 I am trying to model buoyancy.... I was hoping that only buoyancy will move the flow

July 22, 2013, 08:36
#6
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Artem Shaklein
Join Date: Feb 2010
Location: Russia, Izhevsk
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Quote:
 Originally Posted by bigzakk I am trying to model buoyancy.... I was hoping that only buoyancy will move the flow
Then use buoyantSimple(Pimple)Foam. A tutorial with room with hot floor, cold ceiling and adiabatic walls can be found in tutorials/heatTransfer/buoyantSimple(Pimple)Foam/hotRoom

 July 22, 2013, 08:47 #7 New Member   zako Join Date: Apr 2012 Posts: 7 Rep Power: 7 yes thats what I am using now. The question is how will I model the walls in case of atmospheric buoyant flow ?

 July 22, 2013, 09:17 #8 Member   Artem Shaklein Join Date: Feb 2010 Location: Russia, Izhevsk Posts: 43 Rep Power: 9 You want to simulate a case with a boundary with unknown in advance flow direction (in or out) and parameters? I just can't see the problem in describing solid walls (the same way as in non-buoyant flows).

July 22, 2013, 09:19
#9
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Mojtaba Amiraslanpour
Join Date: Jun 2011
Location: Zanjan, Iran
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Quote:
 Originally Posted by bigzakk yes thats what I am using now. The question is how will I model the walls in case of atmospheric buoyant flow ?
If you are going to model a building and simulate the flow around it, just model the building and put it within a big volume which will represent the air.

you can you use ABLInletVelocity for air inlet, and symmetry on lateral and top planes of the volume.

Use appropriate wallFunction on the building, and start the simulation.

or of you are not going to use inlet, just heat up the building walls and see what happens due to buoyancy.

I hope it helps a bit,
Mojtaba
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Complex Heat & Flow Simulation Research Group
If you can't explain it simply, you don't understand it well enough. "Richard Feynman"

 July 22, 2013, 09:23 #10 New Member   zako Join Date: Apr 2012 Posts: 7 Rep Power: 7 Thanks a lot guys

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