Menu

Discussion Forum

New Discussion
Filter

Note: This discussion is about an older version of the COMSOL Multiphysics® software. The information provided may be out of date.

Discussion Closed This discussion was created more than 6 months ago and has been closed. To start a new discussion with a link back to this one, click here.

natural convection

Posted Dec 20, 2011, 5:04 a.m. EST Fluid & Heat, Heat Transfer & Phase Change, Computational Fluid Dynamics (CFD) Version 4.2 5 Replies

Byungdal So
Send Private Message Flag post as spam

Please login with a confirmed email address before reporting spam

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 Feb 9, 2012, 2:08 a.m. EST
Lechoslaw Krolikowski
Send Private Message Flag post as spam

Please login with a confirmed email address before reporting spam

Posted: 1 decade ago Dec 20, 2011, 8:12 a.m. EST
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
Send Private Message Flag post as spam

Please login with a confirmed email address before reporting spam

Posted: 1 decade ago Dec 21, 2011, 3:48 p.m. EST
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
Send Private Message Flag post as spam

Please login with a confirmed email address before reporting spam

Posted: 1 decade ago Dec 22, 2011, 4:16 a.m. EST
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
Send Private Message Flag post as spam

Please login with a confirmed email address before reporting spam

Posted: 1 decade ago Dec 23, 2011, 9:33 a.m. EST
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
Send Private Message Flag post as spam

Please login with a confirmed email address before reporting spam

Posted: 1 decade ago Feb 9, 2012, 2:08 a.m. EST
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 ?

Attachments:

Note that while COMSOL employees may participate in the discussion forum, COMSOL® software users who are on-subscription should submit their questions via the Support Center for a more comprehensive response from the Technical Support team.

Suggested Content