# Strange behaviour in a thermalBaffle with radiation

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April 25, 2016, 16:58
Strange behaviour in a thermalBaffle with radiation
#1
Senior Member

Alex
Join Date: Oct 2013
Posts: 337
Rep Power: 20
Hi everybody!

It's been a while since tha last thread I opened here, I hope nobody missed me too much... Otherwise, I'm back anyway!

Well...Let's stick to the point! I have a web site where I am trying to do a kind of user's guide for beginners with some very basic tutorials explained and detailed in order to make them the most clear and understandable I can. A couple of days ago I was preparing a tutorial based on the circuitBoardCooling tutorial but readapted in order to account only for radiation. I talked about this case some months ago in the thread below

possible-bug-fvdom-when-odd-number-ntheta-used

However, in that thread I modified the geometry so that the case was only made up of baffles of the type thermalBaffle1D because I used to have some trouble with the 3D thermal baffles. Now (that I'm older and wiser ) I finally got the case working with 3D baffles (I did a very dumb mistake in the past...), thus, I wanted to upload the case to my web site with the possibility to use them. Here you can find the final test case and the explanation of all the modifications I did:

And now, here comes the problem! When running the case with 1D baffles the results seem to be reasonable, I mean, a thermal distribution in the baffle that receives the radiation exist. However, when I run the same case but beeing the baffle that receive the radiation a 3D baffle everything goes away... the temperature at the end of the simulation is constant all along the baffle (but different from the initial value!). I attach the pictures of the residual plots.

Residual plot of the case when the baffle is 1D

Residual plot of the case when the baffle is 3D

Residual plot of the 3D baffle region

I apologize for the size of the pictures, I don't know how to resize them... If someone lets me know how to do that I will edit the post to fix it!

And regarding the problem with the simulation, can anyone tell me what is wrong with the run? Am I doing something wrong? Is there a bug with the 3D thermal baffles when it comes to calculate the radiative contribution?

Best regards,

Alex
Attached Images
 residuals_1Dbaffle.jpg (87.0 KB, 91 views) residuals.jpg (120.0 KB, 91 views) residuals_baffleRegion.jpg (65.5 KB, 95 views)
__________________
Web site where I present my Master's Thesis: foamingtime.wordpress.com

The case I talk about in this site was solved with chtMultiRegionSimpleFoam solver and involves radiation. Some basic tutorials are also resolved step by step in the web. If you are interested in these matters, you are invited to come in!

 May 2, 2016, 11:30 #2 Senior Member   Alex Join Date: Oct 2013 Posts: 337 Rep Power: 20 Can anyone help me find a solution to my problem, please? Has anyone faced this problem before? Many thanks in advance! __________________ Web site where I present my Master's Thesis: foamingtime.wordpress.com The case I talk about in this site was solved with chtMultiRegionSimpleFoam solver and involves radiation. Some basic tutorials are also resolved step by step in the web. If you are interested in these matters, you are invited to come in!

 October 1, 2016, 17:23 #3 Senior Member     Sergei Join Date: Dec 2009 Posts: 259 Rep Power: 20 Hi, Alex I haven't played with baffles yet, but I see how they could be possibly useful for me in the near future. Can they be used in surface-to-surface (viewFactor) radiation?

 Tags 3d thermal baffles, circuitboardcooling, fvdom, radiation, thermal baffles