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Old   July 19, 2013, 05:37
Default Boundary condition in outdoor flow
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zako
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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

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Old   July 21, 2013, 20:34
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What do you mean by no wind flow?
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Old   July 22, 2013, 03:22
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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.

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Old   July 22, 2013, 08:10
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Quote:
Originally Posted by bigzakk View Post
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?
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Old   July 22, 2013, 08:21
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I am trying to model buoyancy.... I was hoping that only buoyancy will move the flow
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Old   July 22, 2013, 08:36
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Quote:
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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
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Old   July 22, 2013, 08:47
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yes thats what I am using now. The question is how will I model the walls in case of atmospheric buoyant flow ?
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Old   July 22, 2013, 09:17
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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).
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Old   July 22, 2013, 09:19
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Quote:
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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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Old   July 22, 2013, 09:23
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Thanks a lot guys
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