Calculation on natural convection with CS

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11 years 4 months ago #4290 by Alicia
Hi all !

I'm currently running a calculation of flow driven by natural convection in a greenhouse.
I have no air inlet, only the ground inside the greenhouse is heated, and so is the roof. So on these two boundaries I have a condition of fixed temperature.
The greenhouse has an opening on one side and is located in a domain so I can see the flow outside. I have an outlet condition on the top and right surfaces of this domain. The files describing my problem are attached here.

My problem is that when I look at the results, I have a vertical flow through the ground, which is defined as a wall (smooth, non sliding, fixed temperature). For me the wall condition means that the fluid can not go through the surface, and the transverse velocity component is zero (I'm not really sure about this point). I don't really get why I can have such big vertical velocities on the ground surface, whereas these vertical velocities right near the ground are negligeable...

Another little question : As I have no inlet and an outlet, I have a mass flow going out of my domain (something like 1e-2), but no mass flow coming in.. is it possible (as the mass should be conserved) ?

Can somebody give me a hint on this ??

I didn't run the calculation up to the steady state because I'm not sure of this... So I give you a screenshot of the veloctiy field and a screenshot of the temperature field (just so you have an idea of the geometry of the domain) at an arbitrary instant, the vertical velocities at the ground being present all along the iterations. I attach the xml file and the listing as well.

Thank you very much in advance,

Alicia<br /><br />Post edited by: Alicia, at: 2010/05/26 19:08
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11 years 4 months ago #4291 by Alicia
Here are the files

Attachment Greenhouse_Files-064571e87cff383dc7cf2d9d32220011.gz not found

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11 years 3 months ago #4445 by wwiki
Hi Alicia ,

Just for information. I would run your example on cs2.0 .
But xml file look to old.

Are you using 1.3.3 version ?

:blush:

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11 years 2 months ago #4494 by florante
Replied by florante on topic Re:Calculation on natural convection with CS
Hi,

the small amount of mass that get out of your system without being replaced could possibly be a result to the change of fluid density inside the domain. without a change in mass , the total pressure would be slightly greater than the reference due to the presence heat. If your average pressure is has not change, then your mass should change since there is a temperature change

[code:1]
pv=mrt
[/code:1]

my one cent.

Florante

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11 years 2 months ago #4495 by florante
Replied by florante on topic Re:Calculation on natural convection with CS
Alicia,

can you post the mesh so that I could try ? (learning)


thanks

Florante

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11 years 2 months ago #4573 by Alicia
Thank you all for your help,
unfortunately I could not continue this case as I didn't have time for this. It was just a test case I would have liked to run because it was interesting. I can not post the mesh either because it is too big...

I can not post either the article in which I found the case for the same reason, but here is the title : &quot;Comparison of finite element and finite volume methods for simulation of natural ventilation in greenhouses&quot;.


By the way I was using CS 1.4.b, but now I'm using cs 2.0-rc2, but don't have time at all to come back on the calculation...

Thanks again, I appreciate the effort ! :)

Alicia<br /><br />Post edited by: Alicia, at: 2010/08/18 18:26

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