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Heat transfer, natural convection: Heat sink <-> Air |
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November 11, 2013, 06:18 |
Heat transfer, natural convection: Heat sink <-> Air
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#1 |
New Member
Sven
Join Date: Nov 2013
Posts: 7
Rep Power: 12 |
Hi everybody,
in the last weeks I tried to start with OpenFOAM and I would like to solve the following case: The attached Heat sink gets a Heat Flux of 50 W on its lower surface. The natural convection of the air arround the Heat sink cools it. Seems to be a simple case. I want to solve it with the chtMultiRegionSimpleFoam solver because all i need is the steady state (right solver?). I can't find a description how to load my heatsink.stl file and to create a air box around it. The tutorials don't give enough hints except that I could use a refinementBox (searchableBox) for this. My Questions: - What is the best tutorial I can build up my case with? - How do I load my STL file into this case? - How can I create the Airbox? - How does OpenFOAM know what is the solid and what is the fluid? I'm happy about every help I get. Thanks |
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November 11, 2013, 09:08 |
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#2 |
New Member
Michael
Join Date: Sep 2012
Posts: 23
Rep Power: 14 |
The best starting point would be the chtMultiRegionFoam tutorial snappyMultiRegionHeater.
Study the Allrun-script and the whole case structure and all files. If you would like to get a correct solution you will also need to add a radiation model, either viewFactor (chtMultiRegionSimpleFoam/multiRegionHeaterRadiation) or fvDOM (buoyantSimpleFoam/hotRadiationRoomFvDOM). Furthermore you have to study which boundary conditions you need for natural convection. |
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November 11, 2013, 09:36 |
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#3 |
New Member
Sven
Join Date: Nov 2013
Posts: 7
Rep Power: 12 |
Hi mirx,
thank you for your reply. I started with snappyMultiRegionHeater already. I tried to run the case with only two regions: heater and topAir. I commented the other regions out in every file I found. Code:
--> FOAM FATAL ERROR: Attempt to cast type calculated to type compressible::turbulentTemperatureCoupledBaffleMixed From function refCast<To>(From&) in file /home/opencfd/OpenFOAM/OpenFOAM-2.2.2/src/OpenFOAM/lnInclude/typeInfo.H at line 114. FOAM aborting #0 Foam::error::printStack(Foam::Ostream&) at ??:? #1 Foam::error::abort() at ??:? #2 Foam::compressible::turbulentTemperatureCoupledBaffleMixedFvPatchScalarField::updateCoeffs() at ??:? #3 Foam::mixedFvPatchField<double>::evaluate(Foam::UPstream::commsTypes) at ??:? #4 Foam::mixedEnergyFvPatchScalarField::updateCoeffs() at ??:? #5 Foam::GeometricField<double, Foam::fvPatchField, Foam::volMesh>::GeometricBoundaryField::updateCoeffs() at ??:? #6 Foam::fvMatrix<double>::fvMatrix(Foam::GeometricField<double, Foam::fvPatchField, Foam::volMesh> const&, Foam::dimensionSet const&) at ??:? #7 at ??:? #8 at ??:? #9 __libc_start_main in "/lib/x86_64-linux-gnu/libc.so.6" #10 at ??:? Aborted (core dumped) https://dl.dropboxusercontent.com/u/...HeaterSven.zip |
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November 11, 2013, 10:18 |
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#4 |
New Member
Michael
Join Date: Sep 2012
Posts: 23
Rep Power: 14 |
splitMeshRegion created a third region: domain0.
This region is present in your boundary files: constant/heater/polyMesh/boundary Code:
heater_to_domain0 { type mappedWall; nFaces 430; startFace 1555; sampleMode nearestPatchFace; sampleRegion domain0; samplePatch domain0_to_heater; offsetMode uniform; offset (0 0 0); } |
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November 12, 2013, 07:51 |
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#5 |
New Member
Sven
Join Date: Nov 2013
Posts: 7
Rep Power: 12 |
That was a nice advice! Like the other regions I removed the topAir now and made domain0 fluid in constant/regionProperties. Where can I set the size of the box? I don't understand the code of blockMeshDict, but maybe I will find out by searching the Internet in the next minutes
I copied the properties (g, radiationProperties, thermophysicalProperties etc.) into the constant/domain0 folder. After running it again, I got a "new" error: Code:
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * // Create time Create fluid mesh for region domain0 for time = 0 Create solid mesh for region heater for time = 0 *** Reading fluid mesh thermophysical properties for region domain0 Adding to thermoFluid Selecting thermodynamics package { type heRhoThermo; mixture pureMixture; transport const; thermo hConst; equationOfState perfectGas; specie specie; energy sensibleEnthalpy; } #0 Foam::error::printStack(Foam::Ostream&) at ??:? #1 Foam::sigFpe::sigHandler(int) at ??:? #2 in "/lib/x86_64-linux-gnu/libc.so.6" #3 Foam::heRhoThermo<Foam::rhoThermo, Foam::pureMixture<Foam::constTransport<Foam::species::thermo<Foam::hConstThermo<Foam::perfectGas<Foam::specie> >, Foam::sensibleEnthalpy> > > >::calculate() at ??:? #4 Foam::rhoThermo::addfvMeshConstructorToTable<Foam::heRhoThermo<Foam::rhoThermo, Foam::pureMixture<Foam::constTransport<Foam::species::thermo<Foam::hConstThermo<Foam::perfectGas<Foam::specie> >, Foam::sensibleEnthalpy> > > > >::New(Foam::fvMesh const&, Foam::word const&) at ??:? #5 Foam::autoPtr<Foam::rhoThermo> Foam::basicThermo::New<Foam::rhoThermo>(Foam::fvMesh const&, Foam::word const&) at ??:? #6 Foam::rhoThermo::New(Foam::fvMesh const&, Foam::word const&) at ??:? #7 at ??:? #8 __libc_start_main in "/lib/x86_64-linux-gnu/libc.so.6" #9 at ??:? Floating point exception (core dumped) EDIT: The box is bigger now. https://dl.dropboxusercontent.com/u/...eaterSven2.zip |
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November 12, 2013, 13:11 |
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#6 |
New Member
Sven
Join Date: Nov 2013
Posts: 7
Rep Power: 12 |
I learned a bit about meshing with snappyHexMesh today and my heat sink is part of the case now.
Can anybody help me with that error from my last post? And where do I define the heat source on my heat sink? Case: https://dl.dropboxusercontent.com/u/...eaterSven3.zip |
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November 12, 2013, 14:13 |
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#7 |
New Member
Michael
Join Date: Sep 2012
Posts: 23
Rep Power: 14 |
Try to get a proper mesh an case structure first. You have domain(0-10) and no mesh for the heatsink.
I would recommend to use volumetric heat fluxes instead of surface heat fluxes. This is much more realistic. Either you assign a volumetric heat flux on the heatsink itself, or you create a second body, which represents the heater and is in contact with the heatsink. A volumetric heat flux can be created by fvOptions (scalarSemiImplicitSource). |
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November 13, 2013, 03:18 |
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#8 |
New Member
Sven
Join Date: Nov 2013
Posts: 7
Rep Power: 12 |
For me it looks like the heatsink has a mesh And why are there now 11 domains? Do the domains all need the fluid properties?
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November 13, 2013, 04:00 |
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#9 |
New Member
Michael
Join Date: Sep 2012
Posts: 23
Rep Power: 14 |
The domains seem to be from a previous mesh run, which failed.
Run the attached Allclean script. It removes all domains except domain0. Then mesh again. |
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November 13, 2013, 04:35 |
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#10 |
New Member
Sven
Join Date: Nov 2013
Posts: 7
Rep Power: 12 |
Thanks mirx!
Now I have only the heater and domain0 again. I still try to fix the error. It seems that there is something wrong with the thermophysicalProperties in domain0, right?. I started to change some of these properties but this results in other (fatal) errors. The mesh of the heatsink is OK? |
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March 11, 2020, 04:40 |
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#11 |
New Member
pranay
Join Date: Mar 2020
Posts: 7
Rep Power: 6 |
hi i am also working on the similar case did you completed the case simulation...
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