Size of PML for acoustics

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Hi I am trying to solve an acoustic structure interaction model. I am following the tonpilz transducer example from the COMSOL library to set up my case. I am not sure about the size of the PML region. If I doing a frequency sweep, should I set it up as one wavelength thick? Problem is my device of interest is 10010010 mm size and the maximum frequency of interest is 1 kHz which gives a wavelength is air of 0.2 mm. This will create an unrealistically larger PML.

Is that correct? And if so, any recommendations on number of elements to be put in the PML?


3 Replies Last Post Mar 8, 2022, 2:28 p.m. EST

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Posted: 4 months ago Jan 20, 2022, 1:26 p.m. EST

Apologies, I noticed the size of the device did not show up correctly. Its 100 mm by 100 mm by 10 mm.

Apologies, I noticed the size of the device did not show up correctly. Its 100 mm by 100 mm by 10 mm.

Acculution ApS Certified Consultant

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Posted: 4 months ago Jan 31, 2022, 2:00 a.m. EST

The actual thickness of the PML layer is not important as stated here (https://doc.comsol.com/5.5/doc/com.comsol.help.aco/aco_ug_pressure.05.106.html). Try and get some regular elements though, and at least a couple of them in the thickness direction.

-------------------
René Christensen, PhD
Acculution ApS
www.acculution.com
info@acculution.com
The actual thickness of the PML layer is not important as stated here (https://doc.comsol.com/5.5/doc/com.comsol.help.aco/aco_ug_pressure.05.106.html). Try and get some regular elements though, and at least a couple of them in the thickness direction.

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Posted: 3 months ago Mar 8, 2022, 2:28 p.m. EST

Hi Rene I just saw this, so thank you for the pointing it out. I realized that for the frequency sweep (though simulation wise i see some minor differences, maybe due to mesh convergence?) Anyways, my primary interest is in running time dependant simulations and the guide is not so helpful in that manner apart from saying that "it matters". So, is there any guideline here apart from just trying different sizes? Should it be a factor of the frequenct of interest like 1 wavelength thick?

Hi Rene I just saw this, so thank you for the pointing it out. I realized that for the frequency sweep (though simulation wise i see some minor differences, maybe due to mesh convergence?) Anyways, my primary interest is in running time dependant simulations and the guide is not so helpful in that manner apart from saying that "it matters". So, is there any guideline here apart from just trying different sizes? Should it be a factor of the frequenct of interest like 1 wavelength thick?

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