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March 20, 2013, 04:47 
Heat conduction problems in OF220

#1 
New Member
Join Date: Apr 2011
Location: Magdeburg, Germany
Posts: 23
Rep Power: 7 
Hello FOAMers,
I actually want to simulate a cht problem with many different regions in OpenFOAM 2.2.0. But when I simulated a little test case, there occur differences in heat conduction from OF 2.1.1 to 2.2.0. You can therefore have a look at the attached picture. I took the flange case out of the laplacianFoam tutorial. Then I adjusted the material properties for cp, rho and kappa in this way that I should get the same results for laplacianFoam solver and chtMultiRefionFoam solver. (In laplacianFoam we have just DT, which can be calculated as: DT = kappa/(cp*rho) ) The results for laplacianFoam and cht  OF211 simulation are similar. Unfortunately the cht  OF220 simulation differs from that. So my question is, does anyone know what the problem is in this case? Is it maybe a bug of the new version? Best regards, Nico 

March 20, 2013, 05:35 

#2 
New Member
Join Date: Apr 2011
Location: Magdeburg, Germany
Posts: 23
Rep Power: 7 
I also looked at the source code of solveSolid.H in the cht solver. The TEqn for OF211 is:
Code:
for (int nonOrth=0; nonOrth<=nNonOrthCorr; nonOrth++) { tmp<fvScalarMatrix> TEqn ( fvm::ddt(rho*cp, T)  fvm::laplacian(kappa, T) ); TEqn().relax(); TEqn().solve(mesh.solver(T.select(finalIter))); } Code:
for (int nonOrth=0; nonOrth<=nNonOrthCorr; nonOrth++) { tmp<fvScalarMatrix> hEqn ( fvm::ddt(betav*rho, h)  fvm::laplacian(betav*alpha, h, "laplacian(alpha,h)") == fvOptions(rho, h) ); hEqn().relax(); fvOptions.constrain(hEqn()); hEqn().solve(mesh.solver(h.select(finalIter))); fvOptions.correct(h); } Once more, best regards, Nico 

June 15, 2013, 07:37 

#3 
New Member
ali
Join Date: Aug 2012
Posts: 5
Rep Power: 6 
Hi Nico A,
i'm also interested in solving multiregion heat transfer and currently testing the solver chtMultiRegionFoam. Have you figured out what 'betav' in createSolidFields.H means? Thx! 

September 4, 2013, 13:38 

#4 
Member
Xiangyin Meng
Join Date: Jun 2012
Location: London
Posts: 70
Rep Power: 6 
I am working on this issue as well. They should be the same things, but still don't understand what 'betav' is.


March 12, 2014, 13:10 

#5 
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Vitor Vasconcelos
Join Date: Jan 2012
Posts: 33
Rep Power: 6 
I'm also interested in understanding betav and fvOptions(rho, h).
Waiting for the enlightenment... 

March 14, 2014, 07:07 

#6 
New Member
akrasemann
Join Date: Dec 2013
Posts: 17
Rep Power: 4 
fvOptions is a utility enabling you to introduce additional terms into the solver, as far as I understand the release notes http://www.openfoam.org/version2.2.0/fvOptions.php.
Regarding the solid region within chtMultiRegionFoam I'm as well curious about the exact meaning of betav. In German textbooks on (solid body) mechanics the thermal volumetric expansion coefficient is sometimes called beta_v, but I do not understand, why this coefficient should be introduced into the solver. 

March 14, 2014, 10:21 

#7  
Member
Vitor Vasconcelos
Join Date: Jan 2012
Posts: 33
Rep Power: 6 
Quote:
Actually, I just removed fvOptions(rho, h) from my solver and added a sourceterm manually. However, I'm still curious on how it works internally. I could check it manupulates a list of pointers to contents in the fvOptions file, but sometimes I have to hold the impetus of try to understand everything in OpenFOAM and just do what I need. Thanks a lot for your help. I'll do the homework researching on "thermal volumetric expansion coefficient" (at this point you probably realized I'm not an engineer) but please, keep us updated if you get more information about the betav in the solver. Thank you! 

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