I'm doing PML simulation, and while I was looking for correct geometry for my layers of propagation, I got a question.

  1. My device has two vibration sources, and this vibration will propagate through the medium and diminish.

I am trying to draw my medium as a cylinder or hemisphere, but since there are two vibration sources, the center of cylinder/hemisphere is an equal distance between two vibrating sources.

here is the picture of how it looks like.

enter image description here

This is a 2D version, but I am simulating this device in 3D version.

The vibration source has out of plane waveform.

Is it okay to simulate like this? I'm afraid this will give incorrect result since vibration sources are not at the center of cylinder/hemisphere.

  1. Or, do I have to cut my device in half and put only one vibrating source on the propagating medium? (symmetric condition should be imposed on the half of resonator device) enter image description here

This second method, I think it seems unrealistic because it excludes the presence of another vibrating source which will cause interference, however, I saw a number of papers simulate their device with two vibrating sources such way.


1 Answer 1


I believe it is OK to use the PML the first way you described. It's not necessary to put the source at the center, otherwise PML is not better than many other absorbing boundary conditions. The PML even doesn't need to be a spherical shell, which is just a choice of convenience.

  • $\begingroup$ But in the first way, the obtained quality factor(Q) is much bigger than the second one. I thought both way should give similar quality factor(Q) but why first one is bigger than second one? (it's by 3 times) $\endgroup$
    – user65452
    Aug 14, 2016 at 0:58
  • $\begingroup$ I doubt the two approaches are equivalent physically. For the first case, the radiated wave from port 1 could feed into port 2, but in the second case such interaction is not possible. So the difference could come from other things. $\endgroup$
    – Pu Zhang
    Aug 15, 2016 at 12:27

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