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natural convection

Posted 20.12.2011, 05:04 GMT-5 Fluid & Heat, Heat Transfer & Phase Change, Computational Fluid Dynamics (CFD) Version 4.2 5 Replies

Byungdal So
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hi all.

this is problem about natural convection.

first, the file I attached, free_convection.mph, is from model gallery. so it works very well. this model has low and high temperature in right and left sides of square.


second, free_convection_modified.mph has low and high temperature in top and bottom of square.
almost are same with "free_convection.mph".
but the result is very strange, the result should be like this " www.youtube.com/watch?v=nveHV29gD-E "

do you guys know what problem is?

ByungDal

5 Replies Last Post 09.02.2012, 02:08 GMT-5
Lechoslaw Krolikowski
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Posted: 1 decade ago 20.12.2011, 08:12 GMT-5
Hi,

I think that you should base on the following example:
Model Library>Heat Transfer Module>Tutorial Models<cold_water_glass,
if you want to simulate natural convection.

Best regards,
Andrzej
Hi, I think that you should base on the following example: Model Library>Heat Transfer Module>Tutorial Models
Nagi Elabbasi Facebook Reality Labs
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Posted: 1 decade ago 21.12.2011, 15:48 GMT-5
This is an interesting problem that you’re trying to analyze. It is an unstable Rayleigh-Benard convection problem. I think you need a much finer mesh and a transient analysis for reach Ra value. To see if the basic settings you have are reasonable I tried switching the hot/cold boundaries to the side walls instead of the top and bottom boundaries and it works as expected (it’s a different problem of course, but one that is much more stable).

Nagi Elabbasi
Veryst Engineering
This is an interesting problem that you’re trying to analyze. It is an unstable Rayleigh-Benard convection problem. I think you need a much finer mesh and a transient analysis for reach Ra value. To see if the basic settings you have are reasonable I tried switching the hot/cold boundaries to the side walls instead of the top and bottom boundaries and it works as expected (it’s a different problem of course, but one that is much more stable). Nagi Elabbasi Veryst Engineering
Byungdal So
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Posted: 1 decade ago 22.12.2011, 04:16 GMT-5
thank you for your advice.

but I can't understand about using transient analysis for reach Ra.

thank you
thank you for your advice. but I can't understand about using transient analysis for reach Ra. thank you
Nagi Elabbasi Facebook Reality Labs
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Posted: 1 decade ago 23.12.2011, 09:33 GMT-5
I meant for "each" Ra value. The solutions are not trivial, and the convection patterns are not unique. You can also see that in the animation you referred to. A transient analysis is more suitable as it can capture the gradual development of the convective flow.

Nagi Elabbasi
Veryst Engineering
I meant for "each" Ra value. The solutions are not trivial, and the convection patterns are not unique. You can also see that in the animation you referred to. A transient analysis is more suitable as it can capture the gradual development of the convective flow. Nagi Elabbasi Veryst Engineering
Santhosh Kumar CT
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Posted: 1 decade ago 09.02.2012, 02:08 GMT-5
Hi ..

i tried modifying the same problem to 3D with a slightly different geometry.

But i ended up in error statement : "Detail: NaN_or_Inf_found_when_solving_linear_system_using_GMRES"

may i know what mistake(s) did while setting up the problem ?
Hi .. i tried modifying the same problem to 3D with a slightly different geometry. But i ended up in error statement : "Detail: NaN_or_Inf_found_when_solving_linear_system_using_GMRES" may i know what mistake(s) did while setting up the problem ?

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