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Acoustic radiation from vibrating ring
Posted Mar 17, 2011, 11:14 a.m. EDT Acoustics & Vibrations 3 Replies
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Hello!
Please, help me with the following problem:
I study acoustic radiation from flexurally-vibrating ring in air using frequency response analysis and acoustic-structure interaction. In-plane vibrations of the ring are excited by the load distributed along one of its generating lines. Frequency of excitation is 35.8 kHz. Diameter of the ring is 25 mm, thickness is 1 mm. Eigenmode corresponding to these parameters has 12 nodal points and corresponding wavelength is rather small. I tried to create 3D model of the problem, but small wavelength demanded very large number of finite elements and performance of my computer (CPU 2.4 GHz, RAM 2.0 Gb) was insufficient to obtain good resolution of acoustic field pattern. Is it possible to use axially symmetric model for my problem? I have idea how to do it, but I need your advices on practical implementation of this idea. For example, I can perform frequency response analysis without account for air load and determine distribution of radial displacements along the perimeter of the ring. This distribution can be represented as a sum of harmonic functions of angular coordinate with different pitch (azimuthal wavenumber) using Fourier series. Then each harmonic term of Fourier series can be used as input exciting structural load for acoustic-structure interaction analysis. General solution can be obtained as a sum of solutions corresponding to input loads with different azimuthal wavenumbers using superposition principle.
Thank you in advance.
Best regards. Dmitry.
Please, help me with the following problem:
I study acoustic radiation from flexurally-vibrating ring in air using frequency response analysis and acoustic-structure interaction. In-plane vibrations of the ring are excited by the load distributed along one of its generating lines. Frequency of excitation is 35.8 kHz. Diameter of the ring is 25 mm, thickness is 1 mm. Eigenmode corresponding to these parameters has 12 nodal points and corresponding wavelength is rather small. I tried to create 3D model of the problem, but small wavelength demanded very large number of finite elements and performance of my computer (CPU 2.4 GHz, RAM 2.0 Gb) was insufficient to obtain good resolution of acoustic field pattern. Is it possible to use axially symmetric model for my problem? I have idea how to do it, but I need your advices on practical implementation of this idea. For example, I can perform frequency response analysis without account for air load and determine distribution of radial displacements along the perimeter of the ring. This distribution can be represented as a sum of harmonic functions of angular coordinate with different pitch (azimuthal wavenumber) using Fourier series. Then each harmonic term of Fourier series can be used as input exciting structural load for acoustic-structure interaction analysis. General solution can be obtained as a sum of solutions corresponding to input loads with different azimuthal wavenumbers using superposition principle.
Thank you in advance.
Best regards. Dmitry.
3 Replies Last Post Mar 18, 2011, 2:26 a.m. EDT
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Posted:
1 decade ago
Hi
I do not have the acoustic module, and hardly any experience with that field, (but there are other skilled people out here who can probably propose other means ;)
so my only advice is to reduce the model via symmetry, along the lines you propose, possibly in 2-3 steps/directions if 1 is not enough.
Perhaps you can manage to get it into a 2D axi symmetry, but the multiple node oscillation (I understand along the loop length of the torus) are not obvious to reduce
--
Good luck
Ivar
I do not have the acoustic module, and hardly any experience with that field, (but there are other skilled people out here who can probably propose other means ;)
so my only advice is to reduce the model via symmetry, along the lines you propose, possibly in 2-3 steps/directions if 1 is not enough.
Perhaps you can manage to get it into a 2D axi symmetry, but the multiple node oscillation (I understand along the loop length of the torus) are not obvious to reduce
--
Good luck
Ivar
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Posted:
1 decade ago
Thank you for your advice, Ivar.
But I gave slightly incomplete description of my problem. Ring has rectangular cross section (not a torus with circular section!). So I used terms "thickness" (instead of diameter) and "generating line". But in principle your idea about symmetry-based reduction of the model should work for both these geometries.
Best regards. Dmitry.
But I gave slightly incomplete description of my problem. Ring has rectangular cross section (not a torus with circular section!). So I used terms "thickness" (instead of diameter) and "generating line". But in principle your idea about symmetry-based reduction of the model should work for both these geometries.
Best regards. Dmitry.
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Posted:
1 decade ago
Hi
indeed then 2D axi is no good, but you might be able to cut your 3D it in 2, 4 or even more, note often one need to play with the symmetry/antisymmetry conditions and perform several runs, think it over, nothing is fully free ;)
--
Good luck
Ivar
indeed then 2D axi is no good, but you might be able to cut your 3D it in 2, 4 or even more, note often one need to play with the symmetry/antisymmetry conditions and perform several runs, think it over, nothing is fully free ;)
--
Good luck
Ivar