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simulate a stand wave tube

Posted Nov 30, 2016, 7:31 a.m. EST Acoustics & Vibrations, Modeling Tools & Definitions, Parameters, Variables, & Functions, Structural Mechanics Version 5.2a 2 Replies

Wen Hsiung
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hi, everyone. I am new to comsol. I want to make a simulation of measurement of absorption coefficients in standing wave tube;
here are my problem I encountered：
I don't how to add a plane sound wave to a closed wall boundary, I mean
I use a cuboid simulate the air in the tube, and all the surfaces are set hard sound boundary， but how to add a plane sound wave to the air？

i try to set a end surface of cuboid as [plane wave radiation]，and then add [incident pressure field] ,but then this surface is not hard sound boundary.

all I want is to simulate the 1th fig in www.acs.psu.edu/drussell/Demos/SWR/AbsorptionCoeff.pdf.

and here is my cuboid picture.
imgsrc.baidu.com/forum/w%3D580/sign=d9a7f68305f431adbcd243317b36ac0f/ec05b322720e0cf3bcda5dea0346f21fbe09aa4d.jpg
2 Replies Last Post Jan 30, 2017, 12:50 a.m. EST
COMSOL Moderator

Hello Wen Hsiung

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Mads Herring Jensen COMSOL Employee

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Posted: 8 years ago Jan 19, 2017, 4:02 a.m. EST
Hi Wen

I think you want to use the Background Pressure Field domain condition. This will let you set up a plane wave in the system, although this is probably not the same as your measurement setup. I guess that in the setup there is a speaker at one end? To model the speaker I would set the end wall to a normal velocity or displacement condition.

Best regards
Mads
Hi Wen I think you want to use the Background Pressure Field domain condition. This will let you set up a plane wave in the system, although this is probably not the same as your measurement setup. I guess that in the setup there is a speaker at one end? To model the speaker I would set the end wall to a normal velocity or displacement condition. Best regards Mads
Linus
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Posted: 8 years ago Jan 30, 2017, 12:50 a.m. EST
Hi Wen,

You could instead consider the use of "Plane Wave Radiation" boundary condition to generate an incident plane wave at the end of the upstream domain.

In "Plane Wave Radiation" boundary condition, right-click and select "Incident Wave". From here, just define 1 Pa as the pressure amplitude and select the furthest wall as your "speaker".

It should work fine.

--
Regards,
Linus Ang
Hi Wen, You could instead consider the use of "Plane Wave Radiation" boundary condition to generate an incident plane wave at the end of the upstream domain. In "Plane Wave Radiation" boundary condition, right-click and select "Incident Wave". From here, just define 1 Pa as the pressure amplitude and select the furthest wall as your "speaker". It should work fine. -- Regards, Linus Ang

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