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thermal conductivity --> anisotropic material

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Old   July 15, 2010, 01:52
Default thermal conductivity --> anisotropic material
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Hello,

i have a thermal conduction problem.
I need to modell a cylinder with different conductivity values in x,y and z direction. The cylinder is within a metal tube (isotropic material )

I think i can simply create 3 variables in transportproperties. Let's say lambdaX, lambdaY and lambdaZ. But after that i haven't a glue what to do next. (I'm pretty new to OpenFoam).


Thanks in advance.

Toni
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Old   July 19, 2010, 09:12
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Ben K
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You just need to make a volTensorField for your thermal conductivities. In your time=0 directory, create your conductivity field using something like:

Code:
FoamFile
{
    version     2.0;
    format      ascii;
    class       volTensorField;
    object      Ds;
}
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
dimensions      [0 2 -1 0 0 0 0];

internalField   uniform (xx 0 0 0 yy 0 0 0 zz);

boundaryField
{
...
}
where xx yy and zz are the values in the 3 different directions.
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Old   July 20, 2010, 05:26
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Hi,

thanks for your reply.

How will the solver recognize the new file?
Don't i have to modify the solver for that?
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Old   July 20, 2010, 08:19
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Ben K
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You'll have to add the field by:

Code:
volTensorField lambda
(
IOobject
(
"lambda",
runTime.timeName(),
mesh,
IOobject::MUST_READ,
IOobject::AUTO_WRITE
),
mesh
);
Or you could also just make a tensor in your transportProperties file and read it into your solver using

Code:
dimensionedTensor lambda(transportProperties.lookup("lambda"));
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Old   March 21, 2018, 14:42
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Quote:
Originally Posted by benk View Post
You just need to make a volTensorField for your thermal conductivities. In your time=0 directory, create your conductivity field using something like:

Code:
FoamFile
{
    version     2.0;
    format      ascii;
    class       volTensorField;
    object      Ds;
}
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
dimensions      [0 2 -1 0 0 0 0];

internalField   uniform (xx 0 0 0 yy 0 0 0 zz);

boundaryField
{
...
}
where xx yy and zz are the values in the 3 different directions.
can you tell me where to put this code as i am having other properties in transportProperties file which doesnt changes in directions
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Old   March 21, 2018, 20:49
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Peter Baskovich
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Hi Val,
What solver are you using?
Since it's cylindrical, do you want cartesian defined conductivities (x y z) or cylindrical coordinates (ρ,φ,z).
I can help if you are using multi-region solvers such as cht.

Benk's code goes in you solver source, which would then need to be recompiled, are you at that level?

Regards
Peter
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Old   March 22, 2018, 00:41
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If the temperature distribution outside the cylinder is of lesser interest, or if the conductivity there is much larger than in the cylinder, you may think about a coordinate transformation: Change the cross section of the cylinder for a circle to an ellipse according the proportion of conductivity and change its length too.

This gives you at least a forst idea of the solution.
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Old   June 5, 2018, 06:32
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Muhammad Waqas
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Quote:
Originally Posted by pete20r2 View Post
Hi Val,
What solver are you using?
Since it's cylindrical, do you want cartesian defined conductivities (x y z) or cylindrical coordinates (ρ,φ,z).
I can help if you are using multi-region solvers such as cht.

Benk's code goes in you solver source, which would then need to be recompiled, are you at that level?

Regards
Peter

Hi Peter,


I am using cht to model heat transfer between fluid and solid. suppose I have a cylinder and fluid passing across the cylinder. Could you please help me to define anisotropic thermal conductivity. It would be great, if I don't need to recompile a solver.
I am using Cartesian coordinate system. Along radial direction (x and y coordinate) thermal conductivity is same but it is different along axial direction.
Moreover, in both direction (radial and axial), it is temperature dependent.
Thank you


Regards
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Old   June 15, 2018, 00:06
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Hi Muhammad,
My example did not use temperature dependent capacity functions but that shouldn't be too hard to add.
To implement a cylindrical coordinate system edit the thermophysicalProperties file of the domain and make it look like this:
Code:
/*--------------------------------*- C++ -*----------------------------------*\
| =========                 |                                                 |
| \\      /  F ield         | OpenFOAM: The Open Source CFD Toolbox           |
|  \\    /   O peration     | Version:  3.0.1                                 |
|   \\  /    A nd           | Web:      www.OpenFOAM.org                      |
|    \\/     M anipulation  |                                                 |
\*---------------------------------------------------------------------------*/
FoamFile
{
    version     2.0;
    format      ascii;
    class       dictionary;
    object      thermophysicalProperties;
}
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //

thermoType
{
    type            heSolidThermo;
    mixture         pureMixture;
    //transport       constIso;
    transport       constAnIso; //<--this bit
    thermo          hConst;
    equationOfState rhoConst;
    specie          specie;
    energy          sensibleEnthalpy;
}

coordinateSystem //<-- and this bit
{
    type    cartesian;  // global co-ordinate system (redundant)
    origin  (-0.009 0.017861 0);   
    coordinateRotation
    {
        type    cylindrical; // local Cartesian co-ordinates
        //e1      (1 0 0);
        e3      (0 0 1); // axis of rotation
    }
}

mixture
{
    specie
    {
        nMoles      1;
        molWeight   50;
    }

    transport
    {

	kappa   (.1 10 10); //radial tangential longitudinal
    }

    thermodynamics
    {
        Hf      0;
        Cp      50;
    }

    equationOfState
    {
        rho     1000;
    }
}

// ************************************************************************* //
To implement the temperature dependent heat capacity have a look at https://cfd.direct/openfoam/user-guide/thermophysical/
Section 7.1.3, you will probably want janaf or polynomial.
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Old   September 11, 2019, 16:06
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Quote:
Originally Posted by pete20r2 View Post
Hi Muhammad,
My example did not use temperature dependent capacity functions but that shouldn't be too hard to add.
To implement a cylindrical coordinate system edit the thermophysicalProperties file of the domain and make it look like this:
Code:
/*--------------------------------*- C++ -*----------------------------------*\
| =========                 |                                                 |
| \\      /  F ield         | OpenFOAM: The Open Source CFD Toolbox           |
|  \\    /   O peration     | Version:  3.0.1                                 |
|   \\  /    A nd           | Web:      www.OpenFOAM.org                      |
|    \\/     M anipulation  |                                                 |
\*---------------------------------------------------------------------------*/
FoamFile
{
    version     2.0;
    format      ascii;
    class       dictionary;
    object      thermophysicalProperties;
}
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //

thermoType
{
    type            heSolidThermo;
    mixture         pureMixture;
    //transport       constIso;
    transport       constAnIso; //<--this bit
    thermo          hConst;
    equationOfState rhoConst;
    specie          specie;
    energy          sensibleEnthalpy;
}

coordinateSystem //<-- and this bit
{
    type    cartesian;  // global co-ordinate system (redundant)
    origin  (-0.009 0.017861 0);   
    coordinateRotation
    {
        type    cylindrical; // local Cartesian co-ordinates
        //e1      (1 0 0);
        e3      (0 0 1); // axis of rotation
    }
}

mixture
{
    specie
    {
        nMoles      1;
        molWeight   50;
    }

    transport
    {

	kappa   (.1 10 10); //radial tangential longitudinal
    }

    thermodynamics
    {
        Hf      0;
        Cp      50;
    }

    equationOfState
    {
        rho     1000;
    }
}

// ************************************************************************* //
To implement the temperature dependent heat capacity have a look at https://cfd.direct/openfoam/user-guide/thermophysical/
Section 7.1.3, you will probably want janaf or polynomial.
what to take as origin
is it center of the cylinder

Thank you
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