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Note: This discussion is about an older version of the COMSOL Multiphysics® software. The information provided may be out of date.

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Coupling plate and acoustics

Posted 24.03.2013, 17:52 GMT-4 Acoustics & Vibrations, Structural Mechanics Version 4.3a 6 Replies

Nick Teunisse
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Hi everyone,

I'm trying to model a axisymmetric disk in 2D which is actuated with 40kHz in the middle in axial direction which gives a pressure wave in the surrounding air. The air is represented by an cylinder. I coupled the two domains by inward acceleration on the boundaries.

However how do I set prescribed displacement of the middle of the disk to be a sine wave with 40kHz and an amplitude of 0.01m? I want to study the wavefronts in the air, so I have chosen for frequency domain study.

What I did so far:
1) Prescribed displacement in Solid Mechanics, selected a point and set w0 to 0.01[m].
2)Computed a frequency domain study, but there are no pressure waves in my acoustic domain.

I also tried to set the displacement with a sine function and variable t, but that gave an error.

So how should I set the sinusoidal displacement for a correct computation of the wavefronts?

Thanks in advance for helping me!
6 Replies Last Post 30.07.2013, 11:44 GMT-4
Ivar KJELBERG COMSOL Multiphysics(r) fan, retired, former "Senior Expert" at CSEM SA (CH)
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Posted: 1 decade ago 25.03.2013, 02:40 GMT-4
Hi
In frequency domain solver mode, the right side of the main physics equations are defined as amplitudes oscillating at the given frequency. (i.e. forces, displacements ...)

To debug such situation it's often easier to use one physics at the time

Then you must be sure you have coupled the physics correctly, that is normally independent of the solver selection

--
Good luck
Ivar
Hi In frequency domain solver mode, the right side of the main physics equations are defined as amplitudes oscillating at the given frequency. (i.e. forces, displacements ...) To debug such situation it's often easier to use one physics at the time Then you must be sure you have coupled the physics correctly, that is normally independent of the solver selection -- Good luck Ivar
Nick Teunisse
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Posted: 1 decade ago 25.03.2013, 06:13 GMT-4
Hi Ivar,

Thank you for your fast reply and explanation. I found the error, namely I did the coupling by inward acceleration, however I set the a_n to zero. Do you know how I can achieve the same acceleration in the structural domain as in the acoustic domain at the boundary? Because I don't know the acceleration of the structure, so I can't define a_n for every element.

Thanks in advance!
Hi Ivar, Thank you for your fast reply and explanation. I found the error, namely I did the coupling by inward acceleration, however I set the a_n to zero. Do you know how I can achieve the same acceleration in the structural domain as in the acoustic domain at the boundary? Because I don't know the acceleration of the structure, so I can't define a_n for every element. Thanks in advance!
Mads Herring Jensen COMSOL Employee

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Posted: 1 decade ago 25.03.2013, 06:48 GMT-4
Hi Nick

If you have the acoustics module I suggest that you use one of the predefined multiphysics interfaces for acoustic-structure interaction. Here the coupling between solid and fluid is done automatically.

Alternatively, on the acoustic side set a normal acceleration: Type = Acceleration and Acceleration = Acceleration (solid/lemm1) so pick up the acceleration from the solid. On the solid side you then set a boundary load and set Load = Acoustic load per unit area (acpr/pam1). Then you pick up the correct normals and lods.

Best regards
Mads


Hi Ivar,

Thank you for your fast reply and explanation. I found the error, namely I did the coupling by inward acceleration, however I set the a_n to zero. Do you know how I can achieve the same acceleration in the structural domain as in the acoustic domain at the boundary? Because I don't know the acceleration of the structure, so I can't define a_n for every element.

Thanks in advance!


Hi Nick If you have the acoustics module I suggest that you use one of the predefined multiphysics interfaces for acoustic-structure interaction. Here the coupling between solid and fluid is done automatically. Alternatively, on the acoustic side set a normal acceleration: Type = Acceleration and Acceleration = Acceleration (solid/lemm1) so pick up the acceleration from the solid. On the solid side you then set a boundary load and set Load = Acoustic load per unit area (acpr/pam1). Then you pick up the correct normals and lods. Best regards Mads [QUOTE] Hi Ivar, Thank you for your fast reply and explanation. I found the error, namely I did the coupling by inward acceleration, however I set the a_n to zero. Do you know how I can achieve the same acceleration in the structural domain as in the acoustic domain at the boundary? Because I don't know the acceleration of the structure, so I can't define a_n for every element. Thanks in advance! [/QUOTE]
Nick Teunisse
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Posted: 1 decade ago 25.03.2013, 07:10 GMT-4
Dear Mads,

Thank you very much! This was exactly where I was looking for.

This topic can be closed.

Greetings Nick
Dear Mads, Thank you very much! This was exactly where I was looking for. This topic can be closed. Greetings Nick
Yu Y.Y
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Posted: 1 decade ago 15.07.2013, 08:03 GMT-4
Dear Nick,
Would you please share your model. I haved made an actuated plate surrounding by air with EMI and Acoustic models which are coupled by this mean. However, the acoustic prssure in the axial direction is zero. I guess that something is wrong!
thank you very much!
Dear Nick, Would you please share your model. I haved made an actuated plate surrounding by air with EMI and Acoustic models which are coupled by this mean. However, the acoustic prssure in the axial direction is zero. I guess that something is wrong! thank you very much!
Nick Teunisse
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Posted: 1 decade ago 30.07.2013, 11:44 GMT-4
Dear Yu,

I used the computers from my university to run comsol, so I can't check if this file is the correct one. But I think the coupling is used in the file.

EDIT: it seems that my upload doesn't work, so here is a link to the file: dl.dropboxusercontent.com/u/1301385/basis_model_no_optimization.mph

Greetings Nick
Dear Yu, I used the computers from my university to run comsol, so I can't check if this file is the correct one. But I think the coupling is used in the file. EDIT: it seems that my upload doesn't work, so here is a link to the file: https://dl.dropboxusercontent.com/u/1301385/basis_model_no_optimization.mph Greetings Nick

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