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-   -   Free convection (http://www.cfd-online.com/Forums/openfoam-pre-processing/130213-free-convection.html)

Micha69822 February 21, 2014 11:37

Free convection
 
Hey guys,

I try to simulate a verticale plate in the atmosphere. For this case I create a box and on one side I add a small plate. Around I want to have everywhere atmosphere (air). The plate should have an temperature from 333 K and the atmosphere should have 293 K.

However I get always worst results. I think my boundarys are wrong.

Have somebody fixed this issue and can sent me a example case or tell me the right boundarys in the T, U, p_rgh and P file for my plate and the atmosphere?


regards
Michael

sengerandu March 6, 2014 06:08

Please furnish more details
 
Can you please furnish more details like what is the element size, number, layers, etc?

Micha69822 March 6, 2014 07:31

Hello sengerandu,

thank you for your reply.

My first cell ist 0,014 mm thick and the gradient ist 20.

Now I've changed my case. I have a horizontal zylinder. In the vertical I used a symmetrPlane to reduce my mesh. Also I simulate 2D now.

T-File:
Is on atmosphere "inletOutlet" and on the wall ist "fixedValue".

U-File:
For atmosphere I use "pressureInletOutletVelocity" and for the wall I use "fixedValue".

P-File ist "calculated"


I think there ist a problem with the p_rgh file. Here I tried a lot of values:
fixedValue, fixedFluxPressure, zeroGradient, totalPressure for the wall and atmosphere.
And my flow pattern look like worse!


Best wishes
Michael

cristina March 10, 2014 11:35

Micha69822,

¿did you get your case runnin? You are trying to simulate an open environment aren´t you? So am I, but I dont get any physical results....
It must be the boundary conditions...

Cristina

Micha69822 March 10, 2014 14:35

Hi,

yes I did.

My failure was the p_rgh File. The bottom has to defined as "totalPressure" and the atmosphere around has to "inletOutlet". The other BC's the same as I described.

And now I get the right solutions!

cristina March 11, 2014 06:58

1 Attachment(s)
Hi Micha69822,

Which solver are you using? buoyantBoussinesqSimpleFoam? I am trying with SimpleFoam, but I do not find the right BC.
I have flow over a ground in atmospheric conditions.... very simple: inlet (constant wind velocity) outlet, sides and Sky and then the ground....
As you recommended, I am using totalPressure in the outet but I dont get good results...
Can you post your BC more detailed? I also attach you my case, maybe you can help me...

thanks!

Cristina

Micha69822 March 11, 2014 08:41

Hi cristina,

I can't work with your files because I use OpenFOAM Version 2.3.0.
But I see in your blockMeshDict that you have defined all faces as wall. For atmosphere you need patch but there is a different in the Versions?!

cristina March 11, 2014 09:27

Hi,

In effect, when I change the BC to patch it does not even run.... I dont know. Can you detail me your BC? So I can try to do the same?

thank!

Micha69822 March 11, 2014 11:07

1 Attachment(s)
Hello cristina,

my settings in the attachment. I hope it help you?

I forgot to tell you my Sovler. I use the buoyantBoussinesqSimpleFoam and the buoyantSimpleFoam.

cristina March 12, 2014 03:20

Hi Micha,

¿your bottom is a wall? ¿like the ground?
Cristina

Micha69822 March 12, 2014 05:55

Hi,

no. I simulate a pipe an this surface is in my case the wall.


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