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chtMultiRegionFoam natural convection negative initial temperature |
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February 8, 2021, 06:09 |
chtMultiRegionFoam natural convection negative initial temperature
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#1 |
Member
cal
Join Date: Feb 2020
Location: nowhere
Posts: 65
Rep Power: 6 |
Hi,
I'm trying to do turbulent natural convection heat transfer case with chtMultiRegionFoam. The geometry is here. By the way geometry is 3D. The sphere that is at the origin of the coordinate system is 1023.15 K and the fluid (helium) is 523.15K.
For curiosity I changed my case to cavity and made all boundaries wall (adiabatic bc) and it works much better than inlet-outlet one. Unfortunately I want to do this with patches. I think i'm doing something wrong on boundary conditions but i can't figure it out. What should I change, what should I try? I am open to any suggestions. Files are attached. Kind regards, Said. For quick look: Code:
fluid/T internalField uniform $Tinitial; boundaryField { inlet { type fixedValue; value uniform $Tinitial; } outlet { type inletOutlet; inletValue uniform $Tinitial; value uniform $Tinitial; } wall { type zeroGradient; } fluid_to_sphere { type compressible::turbulentTemperatureCoupledBaffleMixed; neighbourFieldName T; kappa kappa; Tnbr T; value uniform $Tinitial; } } Code:
fluid/p_rgh internalField uniform $pInitial; boundaryField { outlet { type fixedValue; value uniform $pInitial; } inlet { type fixedFluxPressure; gradient uniform 0; value uniform $pInitial; } wall { type fixedFluxPressure; gradient uniform 0; value uniform $pInitial; } fluid_to_sphere { type fixedFluxPressure; gradient uniform 0; value uniform $pInitial; } } Code:
fluid/p internalField uniform $pInitial; boundaryField { outlet { type calculated; value uniform $pInitial; } inlet { type calculated; value uniform $pInitial; } wall { type calculated; value uniform $pInitial; } fluid_to_sphere { type calculated; value uniform $pInitial; } } Code:
fluid/U internalField uniform (0 0 0); boundaryField { inlet { type fixedValue; value uniform (0 0 0); } outlet { type pressureInletOutletVelocity; inletValue uniform (0 0 0); value uniform (0 0 0); } wall { type fixedValue; value uniform (0 0 0); } akiskan_to_kure { type fixedValue; value uniform (0 0 0); } } |
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February 8, 2021, 07:58 |
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#3 | |
Member
cal
Join Date: Feb 2020
Location: nowhere
Posts: 65
Rep Power: 6 |
Quote:
When i add temperature limit for fluid region, solver stops iteration after like 200 iterates. I mean 0 iteration, all parameters are stay same. For example, first 200 iteration initial temperature value decreasing but still positive, after 200 iteration initial temperature is becomes negative, after last iteration parameteres never change. kind regards, Said. |
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February 8, 2021, 09:17 |
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#4 |
Super Moderator
Tobias Holzmann
Join Date: Oct 2010
Location: Bad Wörishofen
Posts: 2,711
Blog Entries: 6
Rep Power: 52 |
Check out your fluid field in the domain? The negative temperature should occur in e.g. some cell or due to unphysical values for p and U. A work-around to fix your problem is to start with another solver (without your sphere). E.g., rhoSimpleFoam/rhoPimpleFoam. I supose that there is a problem somewhere else and the outcome destroyes your energy equation. You can also test with "incompressiblePerfectGas".
__________________
Keep foaming, Tobias Holzmann |
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February 8, 2021, 12:59 |
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#5 |
Member
JuanMi
Join Date: Nov 2017
Posts: 41
Rep Power: 8 |
Please attach a runnable example if you want us to help you, with the corresponding scripts (Allrun, etc.). You uploaded a case which is not directly runnable.
A priori your case does not seem too complicated. |
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February 8, 2021, 15:11 |
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#6 | |
Member
cal
Join Date: Feb 2020
Location: nowhere
Posts: 65
Rep Power: 6 |
Quote:
Case file is 85 mb so i can't upload here. link, this is github download link. Rar file has everything you need, just download and type ./Allrun. Also i'll try Tobi's advice as soon as possible. kind regards, Said. |
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February 9, 2021, 07:14 |
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#7 |
Senior Member
Peter Hess
Join Date: Apr 2011
Location: Austria
Posts: 250
Rep Power: 17 |
Hello Sadic
In: templates\0\fluid p_rgh is overall 0. This is not allowed and should be 1.013e5 (if zou have atmospharic pressure). That is the main resion for the negative temperature in this solver. Regards Peter |
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Tags |
chtmultiregionfoam, heat tranfer, les, natural convectin |
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