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March 4, 2011, 08:24 |
slow convergence in chtMultiRegionSimpleFoam
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#1 |
Member
Sven Degner
Join Date: Mar 2009
Location: Zürich
Posts: 55
Rep Power: 17 |
Hi Foamers,
I simulate a cht-case. the case setup for the fluid p{ solver GAMG; tolerance 1e-6; relTol 0.01; } ".*" //other fields { solver PBiCG; //also GAMG tolerance 1e-7; relTol 0.1; //also 0.01 and 0 } The relaxation are T 1; k,omega 0.7; U 0.4; p 0.7; the same for the solid temperaturefield. The problem is the very slow convergence, the delta temprature between the iteration steps (deltat) are something like 0.003 Kelvin !!!???? Im not sure how I come two a faster convergence? I try also relTol from 0.01 and 0. and lower relaxations. But for my eyes the relaxation got high values |
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January 9, 2012, 03:40 |
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#2 |
New Member
Join Date: Aug 2011
Location: Paris
Posts: 20
Rep Power: 15 |
Hi sven82,
I am facing the same problem of low convrgence for T field in the solid region in a CHT case. Have you solved the issu since then ? Thanks in advance M. |
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January 9, 2012, 04:53 |
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#3 |
Member
Ulrich Heck
Join Date: Mar 2009
Location: Krefeld, Germany
Posts: 41
Rep Power: 17 |
Dear all,
we got a much fast convergence for chtMultiRegionSimpleFoam in many cases when we increase the number of iterations for T in the solid region (e.g. more nonOrthogonalCorrectors in the solid regions). Hope this helps. Ulli |
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January 24, 2012, 07:40 |
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#4 |
Member
Tibor Nyers
Join Date: Jul 2010
Location: Hungary
Posts: 91
Rep Power: 17 |
Hi Ull,
great tip, the increased iteration number really helps the cht solver in the solid domain. Anyone with experience on the topic of chtMultiRegionFoam solvers? When to use the steady-state / transient version? |
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October 2, 2014, 10:15 |
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#5 |
Member
ms
Join Date: Mar 2009
Location: West London
Posts: 48
Rep Power: 17 |
I was in the same place, using layers in OF 2.3.0 with compressible::turbulentTemperatureCoupledBaffleMix ed. While I don't understand why convergence is so different with solids with and without layers, my incredibly slow convergence (days with 48 cores, steady state and a few hundred thousand cells) was accelerated by adjusting the relaxation factor for h up from 0.7 to 0.9. I saw no difference with nNonOrthogonalCorrectors as my convergence criteria were being met on the second sub-iteration. Successive iterations caused by setting nNonOrthogonalCorrectors gave no change to h residuals.
Good luck all. Mark. |
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