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choosing the proper physics

Posted 2024年7月16日 GMT-4 16:27 Electromagnetics, RF & Microwave Engineering, Physics Interfaces Version 5.3 1 Reply

Hamed Ahmadnia
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Hi, everyone,

I have a question. In my case study (electrical engineering). I have a rectangular steel box and one of the corners of it is connected to the grounding of the system. Also, I have a few sensors which can be connected to the outer surface of the box and there is a discharge inside of the box (in the middle). I want to see the electromagnetic waves resulting from the discharge and how they can be received by each sensor. As I noted, the grounding point is critical to our work.

Based on my knowledge I must use RF, transient module for my project but the only issue is defining an exact boundary condition to the ground since this module doesn't provide a feature for that. Is there any way to fix this issue? Or is it possible to connect this module to the electrical circuit model? If yes, what feature can be used?

1 Reply Last Post 2024年7月16日 GMT-4 22:22
Robert Koslover Certified Consultant
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Posted: 8 months ago 2024年7月16日 GMT-4 22:22
  1. You need to include enough computational space around your box to represent any fields there that may impact the signals received by your sensors. If there are "ground" cables or surfaces that may be relevant in reflecting waves to your sensors, then you can/should include them, but your model will get bigger, of course. There is no "ground" specification offered because it is simply not meaningful. What matters is EM initial conditions, EM boundary conditions, etc. Specify those conditions appropriately and you will be fine. If you want call a surface or cable a "ground," go ahead. The code doesn't care (and it doesn't need to care, to do the computation).
  2. You talk about a discharge "inside" a steel "box." Even if you model that with real-world steel, if you also assume that your box has no significant openings, then you will have to be careful to accurately compute how much (very little!) RF leaks out, since your tiny penetrating signals may be lost in numerical noise. Modeling thru-the-wall transmission must be done carefully. After all, such a box is an EM shield. Anyway, you might want to take a look at some of the info offered at: https://www.comsol.com/video/modeling-electromagnetic-shielding-in-comsol-multiphysics, among other documentation available online.
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Scientific Applications & Research Associates (SARA) Inc.
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1. You need to include enough computational space around your box to represent any fields there that may impact the signals received by your sensors. If there are "ground" cables or surfaces that may be relevant in reflecting waves to your sensors, then you can/should include them, but your model will get bigger, of course. There is no "ground" specification offered because it is simply not meaningful. What matters is EM initial conditions, EM boundary conditions, etc. Specify those conditions appropriately and you will be fine. If you want call a surface or cable a "ground," go ahead. The code doesn't care (and it doesn't need to care, to do the computation). 2. You talk about a discharge "inside" a steel "box." Even if you model that with real-world steel, if you also assume that your box has no significant openings, then you will have to be careful to accurately compute how much (very little!) RF leaks out, since your tiny penetrating signals may be lost in numerical noise. Modeling thru-the-wall transmission must be done carefully. After all, such a box is an EM shield. Anyway, you might want to take a look at some of the info offered at: https://www.comsol.com/video/modeling-electromagnetic-shielding-in-comsol-multiphysics, among other documentation available online.

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