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chtMultiRegionFoam solid to solid boundaries

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Old   November 6, 2018, 09:40
Default chtMultiRegionFoam solid to solid boundaries
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John Bayldon
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I am having difficulties with the proper region to region boundaries using chtMultregionfoam. for heat transfer



To test I made a very simple model with 3 regions, in a stack, with the top boundary held at 800 and the bottom a symmetry plane. The middle region(buildBlock) has a high thermal conductivity compared to the upper (heater) and lower(filledVolume).


What I see is that the heat flux between the top and middle is very low, the high conductivity region is acting as a thermal barrier!

I'm assuming that I have set up the boundaries incorrectly somehow.


This is from the changeDictionaryDict of the top layer

Quote:

T
{
internalField uniform 300;

boundaryField
{
".*"
{
type zeroGradient;
value uniform 300;
}
heater_to_buildBlock
{
type compressible::turbulentTemperatureCoupledBaffleMix ed;
Tnbr T;
kappaMethod solidThermo;
value uniform 300;
}
maxY{
type fixedValue;
value uniform 800;
}

}
}

The only difference in the thermophysical properties between the regions is in the value of kappa, which s 5 for the upper an lower regions and 50 for the middle region.



Quote:
thermoType
{
type heSolidThermo;
mixture pureMixture;
transport constIso;
thermo hConst;
equationOfState rhoConst;
specie specie;
energy sensibleEnthalpy;
}

mixture
{
specie
{
molWeight 12;
}

transport
{
kappa 5;
}

thermodynamics
{
Hf 0;
Cp 500;
}

equationOfState
{
rho 8000;
}
}

Can anyone suggest what i am getting wrong?
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Old   November 6, 2018, 18:16
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John Bayldon
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I think i may be misinterpreting the results.


and I cant figure out how to delete the thread
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Old   November 6, 2018, 22:45
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Peter Baskovich
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I'll just add that I have found turbulentTemperatureCoupledBaffleMixed to cause slow convergence.
I modified the laplacianFoam solver to take DT (thermal diffusivity) in as a field and I assign varying properties to different cellZones via setFields.
This way the whole problem is one mesh (for all solid) and no explicit coupling is required.
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Old   November 7, 2018, 09:22
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John Bayldon
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Quote:
Originally Posted by pete20r2 View Post
I'll just add that I have found turbulentTemperatureCoupledBaffleMixed to cause slow convergence.
I modified the laplacianFoam solver to take DT (thermal diffusivity) in as a field and I assign varying properties to different cellZones via setFields.
This way the whole problem is one mesh (for all solid) and no explicit coupling is required.

Thanks that sounds like a useful method.

I may do that to validate some aspects of the model, however I ultimately need anisotropic heat conductivity and will probably also need some fluid regions for the final model, so I think I need to keep working with multiregion to get to the end goal.Unless you know a way of including anisotropic conductivity in LaplacianFoam.
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Old   November 7, 2018, 09:27
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Peter Baskovich
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Give me a couple of days, I'm pretty sure I can do it with tensors. I would like to make a cht style solver that uses the proper thermo classes, which make things like heat addition easy but I haven't got that far. I'm working on some problems like this at work now so I'll post here if I develop anything. Do you need arbitrary anisotropy or is it all orthogonal, i.e (condX condY condZ)?
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Old   November 7, 2018, 09:30
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John Bayldon
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Quote:
Originally Posted by pete20r2 View Post
Give me a couple of days, I'm pretty sure I can do it with tensors. I would like to make a cht style solver that uses the proper thermo classes, which make things like heat addition easy but I haven't got that far. I'm working on some problems like this at work now so I'll post here if I develop anything. Do you need arbitrary anisotropy or is it all orthogonal, i.e (condX condY condZ)?

Orthogonal.
Thanks.
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