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Boundary conditions when infinite space material is different than air
Posted Sep 4, 2023, 5:01 a.m. EDT Electromagnetics, RF & Microwave Engineering, Materials 1 Reply
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Hi everyone,
I have a question regarding FEM simulations.
Specifically, we have designed a full-wave electromagnetic model to calculate s-parameters and electric field distribution in Radio Frequency > Electromagnetic Waves, Frequency Domain module. I want to simulate the results when the air surrounds the model and then change that surrounding material from air to, e.g., water.
So what I am interested in is, do I have to apply some different kind of boundary conditions (or change the PML, for example) for the case of changing the surrounding material, or is it enough to just run the simulation when the model is surrounded by air and then simply "sink" the model into the water (i.e., is it enough to just change electric properties of the surrounding material domains)? Is there something else I have to take into account regarding EM waves reflection, transmission and absorption when the space around the simulation model is not air/vacuum?
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Based on what I read in the built-in Help system (and I encourage you to look there too), Comsol's software engineers/programmers appear to have considered and accounted for the impact of non-vacuum materials in computational volumes adjacent to both scattering boundary conditions and PMLs. I have not personally/deliberately confirmed this, to see how well it works, although I think I would have noticed issues in at least some of my past models, if it failed dramatically. Anyway, I encourage you to (at a minimum) run some simple sanity tests for yourself, just to be sure (aka, "trust, but verify." )
-------------------Scientific Applications & Research Associates (SARA) Inc.
www.comsol.com/partners-consultants/certified-consultants/sara