lossly material

How to use openEMS. Discussion on examples, tutorials etc

Moderator: thorsten

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Youry
Posts: 51
Joined: Wed 22 Feb 2012, 12:50

lossly material

Post by Youry » Wed 22 Feb 2012, 13:00

Hello,

I using openEMS since 3 days, so I am very very big beginner.
I looking the SetMaterialProperty to make a lossy materials...
But the example in the comment didn't show any complex value example for 'Epsilon'

So I asking, is it possible to put some complex Epsilon, or lossy matter's property ?
If yes could you show me an example...

Moreover I feel that the description of function (in comment in each function definition) are not extensive, I am right ? If yes, where can I find a complete description of every function ?

I also would like to thanks for this so beautiful software. I really enjoy it.

Thank you for answering.

thorsten
Posts: 1438
Joined: Mon 27 Jun 2011, 12:26

Re: lossly material

Post by thorsten » Thu 23 Feb 2012, 10:52

Hi,

first of all, yes the descriptions (especially for SetMaterialProperty) is still very sparse unfortunately.
I'm thinking about starting a User-Manual using LaTex but this would be still a long way to go and I would need some help to get this done...

To your problem:
Yes you can simulate lossy material, but so far you can only define a material conductivity (kappa).
The reason for that is, FDTD is a time-domain method and complex material (real and imaginary part) properties can not be applied to a time-domain method, since it is a frequency domain concept.

But here is what you can do that will work in a small frequency range:
You have:
epsilon_r = eps_r_real + j * eps_r_imag at frequency f_0

--> kappa = eps_r_imag * (2*pi*f_0) * epsilon_0

Or in case you have a loss tangens (tanD):
--> kappa = tanD * 2*pi*f_0 * epsilon * eps_r

Apply this to openEMS:

Code: Select all

CSX = AddMaterial( CSX, 'LossyMat' );
CSX = SetMaterialProp(CSX,'LossyMat','Epsilon', eps_real, 'Kappa', kappa);
<add your primitives>
But keep in mind, this is only exact for f_0 and a good approximation close to f_0! And please recheck the formulas given above, I tend to mess them up :D

Maybe in the future there will be a Drude material model included in openEMS, this will allow to model material losses over a broader frequency range.

I hope this helps,
regards
Thorsten

Youry
Posts: 51
Joined: Wed 22 Feb 2012, 12:50

Re: lossly material

Post by Youry » Wed 07 Mar 2012, 09:31

Thank you very much thorsten for this precise answer,

I am really glad that we can set conductivity, even for a small frequency range of precision.

I am hurry to see the implement of Drude model, and the LaTeX book of function.

So good luck, and congratulation.
openEMS is really great. I hope this free source will have a very very long life.

thorsten
Posts: 1438
Joined: Mon 27 Jun 2011, 12:26

Re: lossly material

Post by thorsten » Thu 08 Mar 2012, 09:47

I am hurry to see the implement of Drude model, and the LaTeX book of function.
Drude model is already included for a long time ;)

Take a look at "examples/other/Metamaterial_Plane_Wave.m" in the openEMS folder...
But so far it is only the lossless model... maybe soon I will add the losses and make it a full Lorentz-Type model...

regards

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