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Tempearture discontinuity among regions

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Old   June 12, 2023, 11:07
Default Tempearture discontinuity among regions
  #1
TGS
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TGS
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I want to analyses the heat transfer of a fin with a side which is heated upto a constant temperature of 400K. The fin was surrounded by the air which was initially at 300 K. I used chtMultiRegionFoam solver and the simulation was performed without any error. However, as shown in the screenshot of temperature distribution, there is a temperature discontinuity in between regions. To get a temperature distribution over the inter region, do you know what I can do? Do I need to make the mesh finer than this? Or do I need to add kappa Method under the turbulentTemperatureCoupledBaffleMixed function in T? or else, is it ok to add fvmodels of inter region heat transfer to each three regions? .
My T file for air is as follows.


/*--------------------------------*- C++ -*----------------------------------*\
========= |
\\ / F ield | OpenFOAM: The Open Source CFD Toolbox
\\ / O peration | Website: https://openfoam.org
\\ / A nd | Version: 8
\\/ M anipulation |
\*---------------------------------------------------------------------------*/
FoamFile
{
version 2.0;
format ascii;
class volScalarField;
location "0/air";
object T;
}
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //

dimensions [ 0 0 0 1 0 0 0 ];

internalField uniform 300;

boundaryField
{
#includeEtc "caseDicts/setConstraintTypes"

inlet
{
type fixedValue;
value $internalField;
}
outlet
{
type inletOutlet;
value $internalField;
inletValue $internalField;
}
top
{
type zeroGradient;
}
bottom
{
type zeroGradient;
}
frontAndBack
{
type zeroGradient;
}
air_to_fin
{
type compressible::turbulentTemperatureCoupledBaffleMix ed;
value $internalField;
Tnbr T;
}
air_to_heatedBoundary
{
type compressible::turbulentTemperatureCoupledBaffleMix ed;
value $internalField;
Tnbr T;
}




}

// ************************************************** *********************** //



and T file for fin:

/*--------------------------------*- C++ -*----------------------------------*\
========= |
\\ / F ield | OpenFOAM: The Open Source CFD Toolbox
\\ / O peration | Website: https://openfoam.org
\\ / A nd | Version: 8
\\/ M anipulation |
\*---------------------------------------------------------------------------*/
FoamFile
{
version 2.0;
format ascii;
class volScalarField;
location "0/fin";
object T;
}
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //

dimensions [ 0 0 0 1 0 0 0 ];

internalField uniform 300;

boundaryField
{
#includeEtc "caseDicts/setConstraintTypes"

fin_to_air
{
type compressible::turbulentTemperatureCoupledBaffleMix ed;
value $internalField;
Tnbr T;
}

fin_to_heatedBoundary
{
type compressible::turbulentTemperatureCoupledBaffleMix ed;
value $internalField;
Tnbr T;
}
top
{
type zeroGradient;
}
bottom
{
type zeroGradient;
}
frontAndBack
{
type zeroGradient;
}
inlet
{
type zeroGradient;
}
outlet
{
type zeroGradient;
}


}

// ************************************************** *********************** //



and T file for heated Boundary
/*--------------------------------*- C++ -*----------------------------------*\
========= |
\\ / F ield | OpenFOAM: The Open Source CFD Toolbox
\\ / O peration | Website: https://openfoam.org
\\ / A nd | Version: 8
\\/ M anipulation |
\*---------------------------------------------------------------------------*/
FoamFile
{
version 2.0;
format ascii;
class volScalarField;
location "0/heatedBoundary";
object T;
}
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //

dimensions [ 0 0 0 1 0 0 0 ];

internalField uniform 400;

boundaryField
{
#includeEtc "caseDicts/setConstraintTypes"

heatedBoundary_to_air
{
type compressible::turbulentTemperatureCoupledBaffleMix ed;
value $internalField;
Tnbr T;
}

heatedBoundary_to_fin
{
type compressible::turbulentTemperatureCoupledBaffleMix ed;
value $internalField;
Tnbr T;
}
top
{
type zeroGradient;
}
bottom
{
type zeroGradient;
}
frontAndBack
{
type zeroGradient;
}
inlet
{
type zeroGradient;
}
outlet
{
type zeroGradient;
}


}

// ************************************************** *********************** //




2. Though the velocity distribution shows the air flow over the fin, I can’t see the inlet velocity value of 5 m/s for Z direction in legend. The values are seeming not sensible. So, do you know what is the reason behind that? my U file is as follows.
/*--------------------------------*- C++ -*----------------------------------*\
========= |
\\ / F ield | OpenFOAM: The Open Source CFD Toolbox
\\ / O peration | Website: https://openfoam.org
\\ / A nd | Version: 8
\\/ M anipulation |
\*---------------------------------
[]------------------------------------------*/
FoamFile
{
version 2.0;
format ascii;
class volVectorField;
location "0/air";
object U;
}
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //

dimensions [ 0 1 -1 0 0 0 0 ];

internalField uniform (0 0 5);

boundaryField
{
#includeEtc "caseDicts/setConstraintTypes"
inlet
{
type fixedValue;
value uniform (0 0 5);
}
outlet
{
type inletOutlet;
inletValue uniform (0 0 5);
value $internalField;
}
top
{
type noSlip;
}
bottom
{
type noSlip;
}
frontAndBack
{
type zeroGradient;
}

air_to_fin
{
type noSlip;
}
air_to_heatedBoundary
{
type noSlip;
}


}

// ************************************************** *********************** //





Can anyone please help me. I am new to OpenFOAM and this is my first simulation.


Thanks,


TGS









Screenshot from 2023-06-09 10-15-01.jpg

Screenshot from 2023-06-09 10-12-22.jpg

Screenshot from 2023-06-09 10-11-40.jpg
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Old   June 13, 2023, 08:02
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Hey!


It is not impossible that the result you shared is actually correct. The air could be slightly heated near the fins, but the scale rnging from 300 to 400 kelvins prevents you from seeing this. Try to lower the upper bound of your colorscale just to make sure it is not an issue of visualisation.


If you see the air being slightly hotter near the fins, then it is just a matter of how much heat is exchanged, and you could try to lower the air inlet velocity so that the air has more time to heat up.


Check if your thermophysicalProperties have sensible values, especially kappa and Cp. The turbulence model also has an impact.
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Old   June 13, 2023, 08:20
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  #3
TGS
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Dear Alczem,


Thank you very much for your prompt answer and I will make the changes that you asked to my simulation and check it again.

Once again thanks a lot.


Thanks,


TGS
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Old   June 15, 2023, 05:42
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  #4
TGS
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Dear Alczem,


I managed the results with the velocity and it was a problem with the legend in colour map. and temperature variation can be seen when the range is reduced. Thank you very much for the help

Thanks,
TGS

Last edited by TGS; June 15, 2023 at 07:32.
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