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thermal conductivity > anisotropic material 

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July 15, 2010, 02:52 
thermal conductivity > anisotropic material

#1 
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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 

July 19, 2010, 10:12 

#2 
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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 { ... } 

July 20, 2010, 06:26 

#3 
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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? 

July 20, 2010, 09:19 

#4 
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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 ); Code:
dimensionedTensor lambda(transportProperties.lookup("lambda")); 

March 21, 2018, 15:42 

#5  
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Quote:


March 21, 2018, 21:49 

#6 
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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 multiregion 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 

March 22, 2018, 01:41 

#7 
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Uwe Pilz
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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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Uwe Pilz  Die der Hauptbewegung überlagerte Schwankungsbewegung ist in ihren Einzelheiten so hoffnungslos kompliziert, daß ihre theoretische Berechnung aussichtslos erscheint. (Hermann Schlichting, 1950) 

June 5, 2018, 07:32 

#8  
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Quote:
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 

June 15, 2018, 01:06 

#9 
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Peter Baskovich
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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 coordinate system (redundant) origin (0.009 0.017861 0); coordinateRotation { type cylindrical; // local Cartesian coordinates //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; } } // ************************************************************************* // Section 7.1.3, you will probably want janaf or polynomial. 

September 11, 2019, 17:06 

#10  
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bharadwaz
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Quote:
is it center of the cylinder Thank you 

September 27, 2019, 14:58 
New Issue in Anisotropic Conductivity

#11 
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Dear all,
I'm trying to verify the chtMultiRegionFoam (v1706) for the case of anisotropic conductivity (kappa). I'm comparing the results obtained with the following two configurations: 1. Isotropic mode, where I set the following: thermoType { type heSolidThermo; mixture pureMixture; transport constIso; thermo hConst; equationOfState rhoConst; specie specie; energy sensibleEnthalpy; } mixture { ... transport { kappa 170; } ... } 2. Anisotropic mode: thermoType { type heSolidThermo; mixture pureMixture; transport constAnIso; thermo hConst; equationOfState rhoConst; specie specie; energy sensibleEnthalpy; } coordinateSystem { type cartesian; origin (0 0 0); coordinateRotation { type axesRotation; e1 (1 0 0); e2 (0 1 0); } mixture { ... transport { kappa (170 170 170); } ... } For some reason, the results are different (the isotropic case is correct). Anyone here knows why the anisotropic case doesn't replicate the results? Do you see something that is wrongly set in thermophysical properties? Thank you in advance, Eugenio 

September 30, 2019, 04:07 

#12  
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shach
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Hi,
just a hint, when you are using constAnIso solid, be sure at the boundary condition T you are using directionalSolidThermo at kappaMethod. Also add a aniAlpha. The names I am not very sure, you may google it. Maybe this is the reason. Quote:


September 30, 2019, 05:03 

#13  
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Quote:
I needed to define the boundary condition in internal walls (between solids) in the following way: nonIsotropicWall { ... kappaMethod directionalSolidThermo; alphaAni Anialpha; ... } 

September 30, 2019, 09:17 

#14 
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shach
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Good to hear that!
However, I remember I had a problem about this directionalSolidThermo function. Though the result is correct, the wall heat flux calculated by wallHeatFlux function is not correct. I am not sure if its due to my setting or the function itself. So, be careful if you are using wallHeatFlux to calculate the heat flux. 

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