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How to set the thickness parameter for metallic structure

degleve

Hello,

I have trouble selecting the right thickness parameter when applying copper to my structure :

I understand the thickness parameter is supposed to be the thickness of my structure.

I so have four questions :

1. In the case of a mettalic cube of side 5mm, should i set it to 5mm ?

2. I can read on the tutorial that "It is important to note that the thickness applied to metallic or dielectric faces is not a physical thickness. It is only used to determine the surface impedance."

→ Is it contradictory with my understanding of what this parameter should be ?

3. I wish to makemy structure with a thickness smaller than the skin depth. How am I supposed to process ? I understand the specified thickness here should be greater than two times the skin depth. How to proceed then ?

4. I can read this error message when specifying thickness to the one of my antenna :

"
Triangle number: 10
Thickness: 5.00000E-04
Lateral dimension: 2.27696E-04
WARNING 2757: A triangle is too thick as compared to the lateral dimensions for application of the skin effect approximation
WARNING 32383: Further warnings 2757 will be suppressed

—> So I guess it means the skin depth computations are not done for these triangles, and that :

"Further warnings 2757 will be suppressed"

—> Does this mean it concerns all my triangles ?

Thanks,

Pierre

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Evan_Urban

@degleve to answer your questions:

and 2. For a metallic medium we specify a thickness that should be small compared to triangle edge length, so determine a thickness that is greater than skin depth at the frequency. 5mm is large and could be much greater than that length. So, depending on the frequency 0.05mm may work well by being larger than skin depth of the material and also smaller than the triangle edge length. We cannot create regions of solid metallic medium.

3. You can specify your thickness smaller than the skin depth, in that case the "full metallic structure" is only seen as a hollow shell.

4. What you are seeing is that the thickness of the triangle is much larger than the triangle edge length: 5e-4 >2.27696e-4. Therefore you get this warning. This occurs for all triangles that have this issue, may not be all of them but seeing as you get

WARNING 32383: Further warnings 2757 will be suppressed

then it appears you have many triangles with this issue.

degleve

Thanks a lot for you answer.

1. and 2. I understand now that skin depth < thickness < triangle edge

3. I did not know it would be okay to have thickness > skin depth. How is that if the manual specify than it should not be the case ?

4. Indeed this is the case for all my triangles. I will correct this and come back to you :)

Pierre

degleve

Hello again,

Here is a new question :

5. I sometimes have a thickness such as thickness > skin depth. I However need a triangle mesh such as triangle size < skin depth. In such a case, how is it possible to have a thickness which is at the same time more little than the triangle, while still making sense with the real thickness ?

My problem here is that I would here need to have thickness < skin depth to ensure that my triangles are computed correctly, even if this is absurd with my structure.

Any thought ?

Thanks a lot

Evan_Urban

@degleve may I ask what you are trying to simulate? I am curious you are running simulations where triangle edge lengths are in proportion of micrometers, or just in skin-depth proportions. What is your frequency of simulation by chance?

Evan_Urban

Or are you running lower frequency simulations? If this is the case, you can just represent the thickness of the metal as the actual representation of the thickness. As long as it is in proportion to triangle edge length. If you want, please share the model and I can look into it deeper.