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phononic crystal -- Acoustic Structure Interaction

Posted 16.02.2011, 06:28 GMT-5 Acoustics & Vibrations, Structural Mechanics Version 3.5a, Version 4.4 6 Replies

Liu Jun
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hello,

i'm computing the phononic crystal band structure using the Acoustic Structure Interaction modal, and the PC is 2D
square lattice and the unit cell is a circle in a square area. the problem is that when the square is liquid and circle area is solid, the band structure is good. but when the square is solid and circle area is liquid , that's to say, the liquid cylinder in the solid base, the computing result is worse, besides the wanted band , there are many flat bands , which are like the locally resonant mode ,
i'm troubled with it.
can anyone help me solve this problem, and give me a way to remove these flat bands

thanks!!!!
6 Replies Last Post 05.10.2015, 07:11 GMT-4
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Chenguang Huang
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Posted: 1 decade ago 28.05.2012, 15:27 GMT-4
Hello,

Are you still working on phononic crystal bandgap calculation? Thanks.
Hello, Are you still working on phononic crystal bandgap calculation? Thanks.
Azizeh Doost Hoseini
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Posted: 1 decade ago 16.02.2013, 15:25 GMT-5
Hello,

Are you still working on phononic crystal bandgap calculation? Thanks
Hello, Are you still working on phononic crystal bandgap calculation? Thanks
Chris Layman
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Posted: 1 decade ago 16.02.2013, 19:07 GMT-5

hello,

i'm computing the phononic crystal band structure using the Acoustic Structure Interaction modal, and the PC is 2D
square lattice and the unit cell is a circle in a square area. the problem is that when the square is liquid and circle area is solid, the band structure is good. but when the square is solid and circle area is liquid , that's to say, the liquid cylinder in the solid base, the computing result is worse, besides the wanted band , there are many flat bands , which are like the locally resonant mode ,
i'm troubled with it.
can anyone help me solve this problem, and give me a way to remove these flat bands

thanks!!!!


those flat bands are due to band folding, and you cannot remove them to my knowledge.
[QUOTE] hello, i'm computing the phononic crystal band structure using the Acoustic Structure Interaction modal, and the PC is 2D square lattice and the unit cell is a circle in a square area. the problem is that when the square is liquid and circle area is solid, the band structure is good. but when the square is solid and circle area is liquid , that's to say, the liquid cylinder in the solid base, the computing result is worse, besides the wanted band , there are many flat bands , which are like the locally resonant mode , i'm troubled with it. can anyone help me solve this problem, and give me a way to remove these flat bands thanks!!!! [/QUOTE] those flat bands are due to band folding, and you cannot remove them to my knowledge.
Nagi Elabbasi Facebook Reality Labs
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Posted: 1 decade ago 17.02.2013, 20:48 GMT-5
If your structure is a perfect phononic crystal you can get rid of these flat bands by only modeling the first irreducible Brillouin zone.

Nagi Elabbasi
Veryst Engineering
If your structure is a perfect phononic crystal you can get rid of these flat bands by only modeling the first irreducible Brillouin zone. Nagi Elabbasi Veryst Engineering
Chris Layman
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Posted: 1 decade ago 18.02.2013, 11:27 GMT-5

If your structure is a perfect phononic crystal you can get rid of these flat bands by only modeling the first irreducible Brillouin zone.

Nagi Elabbasi
Veryst Engineering



I think they are already employing a primitive cell. Per my understanding these "folded bands" are caused by Bragg scattering and cannot simply be removed. Also, it is mentioned this arises when the host is a solid, but what is the shear wave speed in this solid?, if it is very small (like in PDMS), then the acoustic wavelength is tiny and you get heck of a lot of folding into the 1st BZ. (and they look "flat"), and there is not much you can do about that.

It is possible they are also deaf bands in the sense that they cannot be excited in an actual experiment, but to determine that requires comparing the mode shapes to the symmetry of the input wave, if they are asymmetric then they can be selectively removed.


~Chris
[QUOTE] If your structure is a perfect phononic crystal you can get rid of these flat bands by only modeling the first irreducible Brillouin zone. Nagi Elabbasi Veryst Engineering [/QUOTE] I think they are already employing a primitive cell. Per my understanding these "folded bands" are caused by Bragg scattering and cannot simply be removed. Also, it is mentioned this arises when the host is a solid, but what is the shear wave speed in this solid?, if it is very small (like in PDMS), then the acoustic wavelength is tiny and you get heck of a lot of folding into the 1st BZ. (and they look "flat"), and there is not much you can do about that. It is possible they are also deaf bands in the sense that they cannot be excited in an actual experiment, but to determine that requires comparing the mode shapes to the symmetry of the input wave, if they are asymmetric then they can be selectively removed. ~Chris
Tao Young
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Posted: 9 years ago 05.10.2015, 07:11 GMT-4
Hi,


Now,I'm trying to calculate the band structure of 2D square lattice which is consisting of solid circle in liquid host. I use the Acoustic-solid interaction module of version 4.4.And the boundary condition of square is Floquet periodicity condition,while the boudary condition between liquid and solid is Acoustic-structure boundary condition.But the band is bad,I have tried my best to adapt my model,but I fail again and again.I remember that you have faced the same problem,and it seems that you have solved it ,could you give me some tips to solve this problem? I'm very aprreciated to you,thanks.
Hi, Now,I'm trying to calculate the band structure of 2D square lattice which is consisting of solid circle in liquid host. I use the Acoustic-solid interaction module of version 4.4.And the boundary condition of square is Floquet periodicity condition,while the boudary condition between liquid and solid is Acoustic-structure boundary condition.But the band is bad,I have tried my best to adapt my model,but I fail again and again.I remember that you have faced the same problem,and it seems that you have solved it ,could you give me some tips to solve this problem? I'm very aprreciated to you,thanks.

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