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How to set different thermal conductivity in different direction?

Posted 5 oct. 2012, 01:08 UTC−4 Heat Transfer & Phase Change Version 4.3a 3 Replies

Xiang Qiu
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I am trying to simulate a heat transfer model which includes layers with different thermal conductivity in X-Y direction and Z direction. Is it possible to assign a user defined material and have thermal conductivity as a vector? Any comments are appreciated.
3 Replies Last Post 6 janv. 2013, 04:28 UTC−5
Ivar KJELBERG COMSOL Multiphysics(r) fan, retired, former "Senior Expert" at CSEM SA (CH)
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Posted: 1 decade ago 5 oct. 2012, 01:37 UTC−4
Hi

yes
but you must define an anisotropic "k", or check the physics node and select anisotropic material, it depends slightly in which physics you are

By default isotropic material is choosen and the scalar "k" of the material is distributed on the diagonal of the tensor k11, k22, k33
Also in the latest 4.3 version "material.k" is not even defined, you must chose "material.k11" or sqrt(material.k11^2+ ..) or whatever suits youre model

--
Good luck
Ivar
Hi yes but you must define an anisotropic "k", or check the physics node and select anisotropic material, it depends slightly in which physics you are By default isotropic material is choosen and the scalar "k" of the material is distributed on the diagonal of the tensor k11, k22, k33 Also in the latest 4.3 version "material.k" is not even defined, you must chose "material.k11" or sqrt(material.k11^2+ ..) or whatever suits youre model -- Good luck Ivar
Kamil Dursun
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Posted: 1 decade ago 5 janv. 2013, 10:15 UTC−5
Hello Ivar,
I have a similar question. I defined an anisotropic material in axi-symmetric 2 dimensions. What I get is a 2x2 array where I can fill in the values. However I am not sure which direction the k11, k12 etc. are.
I need to define one k for the r-direction and another for the z-direction.
I guess that k11 is the r-direction and k22 is the z-direction. Is this correct? What are k12 and k21 for?
Thank you for your reply.
Kamil
Hello Ivar, I have a similar question. I defined an anisotropic material in axi-symmetric 2 dimensions. What I get is a 2x2 array where I can fill in the values. However I am not sure which direction the k11, k12 etc. are. I need to define one k for the r-direction and another for the z-direction. I guess that k11 is the r-direction and k22 is the z-direction. Is this correct? What are k12 and k21 for? Thank you for your reply. Kamil
Ivar KJELBERG COMSOL Multiphysics(r) fan, retired, former "Senior Expert" at CSEM SA (CH)
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Posted: 1 decade ago 6 janv. 2013, 04:28 UTC−5
Hi

to check the orientation, load your initial values of your model, and add a plot more coordinate and get your directions.

in 3D you can use the Definition coordinates to define your given orientation, in 2D and 2D-axi also but you should also consider the symmetries you are adding by a 2D or a 2D axi which reduces the DoF available.

normally 11 is along the first coordiante, 22 along the second etc

--
Good luck
Ivar
Hi to check the orientation, load your initial values of your model, and add a plot more coordinate and get your directions. in 3D you can use the Definition coordinates to define your given orientation, in 2D and 2D-axi also but you should also consider the symmetries you are adding by a 2D or a 2D axi which reduces the DoF available. normally 11 is along the first coordiante, 22 along the second etc -- Good luck Ivar

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