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Defining a permittivity and permeability tensor in the RF module

Posted 20 juin 2012, 15:32 UTC−4 RF & Microwave Engineering Version 4.2a 6 Replies

Kene Obi
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Hi Guys,
I'm relatively new to Comsol, I'd like to model an anisotropic material in comsol, however my material should have a permeability and permittivity that are tensors as opposed to scalars, and I am unsure how to proceed.
Under Materials, Comsol allows you to input the chosen permittivity and permeability, but as constants:( Please any help or insight would be much appreciated.
-Thanks,
Kene
6 Replies Last Post 1 déc. 2015, 15:33 UTC−5
Ivar KJELBERG COMSOL Multiphysics(r) fan, retired, former "Senior Expert" at CSEM SA (CH)
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Posted: 1 decade ago 20 juin 2012, 16:53 UTC−4
Hi

have you set your physics node to anisotropic materials ?
Then COSMOL will choose tensor values, or request that you define them in the material node

--
Good luck
Ivar
Hi have you set your physics node to anisotropic materials ? Then COSMOL will choose tensor values, or request that you define them in the material node -- Good luck Ivar
Kene Obi
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Posted: 1 decade ago 20 juin 2012, 19:28 UTC−4
Thanks Ivar, I appreciate your help!
Thanks Ivar, I appreciate your help!
Mahmood Waqas
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Posted: 10 years ago 30 nov. 2015, 01:20 UTC−5
Hi,

I also want to simulate anisotropic media. Can anyone please elaborate the node thing? How can I do this in Comsol. I have tried but fail. I need discussion on this.
Hi, I also want to simulate anisotropic media. Can anyone please elaborate the node thing? How can I do this in Comsol. I have tried but fail. I need discussion on this.
Ivar KJELBERG COMSOL Multiphysics(r) fan, retired, former "Senior Expert" at CSEM SA (CH)
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Posted: 10 years ago 30 nov. 2015, 02:07 UTC−5
Hi

there are a few ways:
a) you define your materials properties (nodes) accordingly
b) you define it in the Physics sub node

Normally anisotropy is defined with respect to a given coordinate system that might not be the default Cartesian one of your model, therefore often you must also define a Coordinate system and refer to the correct coordinates, which might by something like sys2.r, sys2.phi ...

As I find it very easy to get the anisotropic coordinates wrong, I do always plot the new coordinate system and the tensor values in a specific dedicated plot, for that you must set up your Solver, do an "Get Initial Values" and make a coordinate plot + a plot of your tensor values in the desired coordinate system

--
Good luck
Ivar
Hi there are a few ways: a) you define your materials properties (nodes) accordingly b) you define it in the Physics sub node Normally anisotropy is defined with respect to a given coordinate system that might not be the default Cartesian one of your model, therefore often you must also define a Coordinate system and refer to the correct coordinates, which might by something like sys2.r, sys2.phi ... As I find it very easy to get the anisotropic coordinates wrong, I do always plot the new coordinate system and the tensor values in a specific dedicated plot, for that you must set up your Solver, do an "Get Initial Values" and make a coordinate plot + a plot of your tensor values in the desired coordinate system -- Good luck Ivar

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Mahmood Waqas
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Posted: 10 years ago 1 déc. 2015, 13:01 UTC−5
Thanks Ivar for your message. Please see the attached file, you may come to know what exactly I want to do. It will be better if you show me an example on how to change the coordinate system and then define tensors. I have seen last file from you and it helps me a lot.

I want to study the behavior of electromagnetic wave at the interface of two different media, one is isotropic and the other is anisotropic. Please do more discussion with me.

I will really appreciate your cooperation. My email is waqasmahmoodqau@gmail.com

Please illustrate me in detail.

Regards,

Waqas.
Thanks Ivar for your message. Please see the attached file, you may come to know what exactly I want to do. It will be better if you show me an example on how to change the coordinate system and then define tensors. I have seen last file from you and it helps me a lot. I want to study the behavior of electromagnetic wave at the interface of two different media, one is isotropic and the other is anisotropic. Please do more discussion with me. I will really appreciate your cooperation. My email is waqasmahmoodqau@gmail.com Please illustrate me in detail. Regards, Waqas.

Attachments:

Ivar KJELBERG COMSOL Multiphysics(r) fan, retired, former "Senior Expert" at CSEM SA (CH)
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Posted: 10 years ago 1 déc. 2015, 15:33 UTC−5
Hi
You cannot change the equation in the equation window there, but you may adapt the underlying equation used by COMSOL, however then you really must understand all the details under the hood! To start you need to turn "on" the "Equation view" in the preferences, and in the same time the other Advanced tabs too. But it's tricky, as there are many relationships, depending how you define your physics.

The cleanest way is to use the global mathematical entry, instead of the standard physics, and rewrite your physics your way. There is also the Model Builder, but its rather heavy if you do not have got a good training (I have tried a few times but not succeeded to become an expert in that interesting part of COMSOL, yet)

I'm only answering COMSOL questions, when I manage, and find the time, here on the Forum. Otherwise I'm getting in conflict with my own job as systems developer and simulation consultant :)

--
Good luck
Ivar
Hi You cannot change the equation in the equation window there, but you may adapt the underlying equation used by COMSOL, however then you really must understand all the details under the hood! To start you need to turn "on" the "Equation view" in the preferences, and in the same time the other Advanced tabs too. But it's tricky, as there are many relationships, depending how you define your physics. The cleanest way is to use the global mathematical entry, instead of the standard physics, and rewrite your physics your way. There is also the Model Builder, but its rather heavy if you do not have got a good training (I have tried a few times but not succeeded to become an expert in that interesting part of COMSOL, yet) I'm only answering COMSOL questions, when I manage, and find the time, here on the Forum. Otherwise I'm getting in conflict with my own job as systems developer and simulation consultant :) -- Good luck Ivar

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