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k anisotropic (exact values, function of coordinates, normal dist.)

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I would like some help with COMSOL 3.4.
I want to introduce the heat equation (steady state) to estimate the temperature of a block (3D). The k (conductivity) is anisotropic.

1) If I have the exact values of k for all block points, how can these values be imported?
2) If k is a function of x,y,z, how should the txt be, which concerns the called function?
3) If k takes values from a distribution (e.g. normal) in each point, how should I work using Comsol?

Thanks a lot.

3 Replies Last Post 20 mag 2012, 11:03 GMT-4
Ivar KJELBERG COMSOL Multiphysics(r) fan, retired, former "Senior Expert" at CSEM SA (CH)

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Posted: 1 decade ago 19 mag 2012, 04:40 GMT-4
Hi

If you choose an anisotropic k value in the material proerties you need to enter the full tensor, now the values you enter can also be a function of the coordinates x,y,z, r,t.
Personally I prefer to make functions I can plot first to check and then refer to these functions lower down in the programme GUI entries

--
Good luck
Ivar
Hi If you choose an anisotropic k value in the material proerties you need to enter the full tensor, now the values you enter can also be a function of the coordinates x,y,z, r,t. Personally I prefer to make functions I can plot first to check and then refer to these functions lower down in the programme GUI entries -- Good luck Ivar

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Posted: 1 decade ago 20 mag 2012, 07:02 GMT-4
Dear Ivar,

Thank you for your answer, but it didn’t help me so much.
- The txt should be: the first column includes the x points, the second includes the y points, the third includes the z points and the forth includes the k values, right?
- I should call the function in dialog box of isotropic k, right?
- How can I check the values of k using the cross-section plot parameters in Comsol?

George
Dear Ivar, Thank you for your answer, but it didn’t help me so much. - The txt should be: the first column includes the x points, the second includes the y points, the third includes the z points and the forth includes the k values, right? - I should call the function in dialog box of isotropic k, right? - How can I check the values of k using the cross-section plot parameters in Comsol? George

Ivar KJELBERG COMSOL Multiphysics(r) fan, retired, former "Senior Expert" at CSEM SA (CH)

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Posted: 1 decade ago 20 mag 2012, 11:03 GMT-4
Hi

sorry I do not have 3.4 running any longer, but I know v3 was awfull w.r.t plotting tensors ;( That is now much better in the new versions.

Often, but it's tedious, I really went through the internal equations in the equation view, and checked by hand writing out my anisotropic tensors that I got the results as expected w.r.t the way to enter the values (particularly as PZT tensors and elasticitiy tensors have different orders ;)
I know it took some time, but one can get it right like that
--
Good luck
Ivar
Hi sorry I do not have 3.4 running any longer, but I know v3 was awfull w.r.t plotting tensors ;( That is now much better in the new versions. Often, but it's tedious, I really went through the internal equations in the equation view, and checked by hand writing out my anisotropic tensors that I got the results as expected w.r.t the way to enter the values (particularly as PZT tensors and elasticitiy tensors have different orders ;) I know it took some time, but one can get it right like that -- Good luck Ivar

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