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Strange pattern within modes

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Hi,

I am simulatimg a fundamental WG with some curves. Since WG is operated in its fundamental band, no mode significant conversion or reflection is present ( coefficients below -50 dB). So I expect to see a very clean TE10 ( input mode) propagating in the WG, expect for the attenuation given by Ohmic losses ( copper walls ). The problem is that I see some strange structures inside the maximum and the minimum of the propagating TE10 ( you find a picture in attachment). Do you think these structures are significant or could they be given by numerical errors? Do you think I need to refine the mesh ?



3 Replies Last Post 2024年2月1日 GMT+1 15:51
Jeff Hiller COMSOL Employee

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Posted: 7 months ago 2024年2月1日 GMT+1 14:40
Updated: 7 months ago 2024年2月1日 GMT+1 14:29

It does look like your mesh is too coarse.

Jeff

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Jeff Hiller
It does look like your mesh is too coarse. Jeff

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Posted: 7 months ago 2024年2月1日 GMT+1 15:20

Hi, I tried to use the "extremely fine" mesh in the physics-controlled mesh option but the pattern is still identical, why?

thanks in advance

Hi, I tried to use the "extremely fine" mesh in the physics-controlled mesh option but the pattern is still identical, why? thanks in advance

Jeff Hiller COMSOL Employee

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Posted: 7 months ago 2024年2月1日 GMT+1 15:51
Updated: 7 months ago 2024年2月1日 GMT+1 21:05

My guess is that the "extremely fine" setting results in a mesh that, its name notwithstanding, is too coarse to capture the solution. I figure from your screenshot that there may only be ~3 elements across that waveguide. If I am right about that, you will need to use more subtle ways of specifying your mesh than a global setting. The chapter on meshing in the Reference Manual contains valuable advice and examples. For this particular analysis, you may want to consider using a swept mesh for the waveguide, seethis blog post on swept meshes.

Jeff

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Jeff Hiller
My guess is that the "extremely fine" setting results in a mesh that, its name notwithstanding, is too coarse to capture the solution. I figure from your screenshot that there may only be ~3 elements across that waveguide. If I am right about that, you will need to use more subtle ways of specifying your mesh than a global setting. The chapter on meshing in the Reference Manual contains valuable advice and examples. For this particular analysis, you may want to consider using a swept mesh for the waveguide, see [this blog post on swept meshes](https://www.comsol.com/blogs/improving-your-meshing-with-swept-meshes/). Jeff

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