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Discrepancy between Time dependent and Frequency Domain Solvers

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Hi,

I'm trying to model surface acoustic wave propagation. I have an interdigitated transducer on a piezoelectric as a source, however I don't think I fully understand how different solvers work. When I use a FD solver, I get waves that look reasonable. However, if I instead use time dependent solver, and replace my electrode voltage with a time dependent expression (Voltage.sin(2.pi.freq.t)), I get no wave propagation whatsoever over many periods.

Moreover, if I use a FD solver followed by Time Dependent solver as a second step, I see that the waves I get are standing waves- which should not be the case. My device is surrounded by Perfectly Matched Layers on all sides to avoid reflection, and I expect only a travelling wave along the device length, that would be absorbed by the PML at the end- so there is no reflection that could cause standing waves.

I would greatly appreciate if someone explained why I get different results with these solvers, and why the Frequency Domain study seems to find standing waves when there should be only travelling waves in the device.


0 Replies Last Post 2 mars 2018, 08:11 UTC−5
COMSOL Moderator

Hello Aleksander Lasek

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