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cantilever frequency response in a fluid

Posted Jun 23, 2010, 11:19 a.m. EDT Version 3.5a 6 Replies

Teddy Maillot
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Hi,

I need to simulate a cantilever which vibrates in a fluid (for instance water) and observe his frequency response.
To do that, I used 4 modules : 2 MEMS Plane Strain modules (1 for frequency response, 1 for fluid effect on the cantilever), 1 Mobile Mesh ALE module and the last is Incompressible Navier Stokes.

Except the MEMS Module for frequency response, all of the modules are transient analysis study.


Until now, when I plot the amplitude of the displacement, I get only the one which correspond to a cantilever in vaccum.
So I think there is a problem whit Navier Stokes module and parameters.

Anyone has an idea how to do this simulation ?

I used the version 3.5a of Comsol Multiphysic. I work with a 2D model

Thank you.

Teddy Maillot
6 Replies Last Post Apr 13, 2011, 1:05 p.m. EDT
Alessandro Ricci
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Posted: 1 decade ago Jun 23, 2010, 11:35 a.m. EDT
Hi Teddy,
give a look to the pdf file: FSI Analysis of Microcantilevers Vibrating in Fluid Environment.
You find it in the "Paper & Presentations" section.
All models are in 3D but I think it is quite easy to convert them in 2d. No ale module is employed and all analyses are of "Damped Eigenfrequency" type.
I hope this helps.

Alessandro
Hi Teddy, give a look to the pdf file: FSI Analysis of Microcantilevers Vibrating in Fluid Environment. You find it in the "Paper & Presentations" section. All models are in 3D but I think it is quite easy to convert them in 2d. No ale module is employed and all analyses are of "Damped Eigenfrequency" type. I hope this helps. Alessandro
Teddy Maillot
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Posted: 1 decade ago Jun 23, 2010, 11:43 a.m. EDT
Hi Alessandro,

Thanks for this. I will take a look at it.

Teddy.
Hi Alessandro, Thanks for this. I will take a look at it. Teddy.
Teddy Maillot
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Posted: 1 decade ago Jun 25, 2010, 10:06 a.m. EDT
Hi

I read the article but when I try to run the simulation, I get the error : singular matrix (with a 2D and a 3D model).

I didn't really understand how to replace the time derivatives by "*jomega_smsld" (page 5, paragraph 3) for the Navier Stokes module.

Thank you


Teddy.
Hi I read the article but when I try to run the simulation, I get the error : singular matrix (with a 2D and a 3D model). I didn't really understand how to replace the time derivatives by "*jomega_smsld" (page 5, paragraph 3) for the Navier Stokes module. Thank you Teddy.
Ivar KJELBERG COMSOL Multiphysics(r) fan, retired, former "Senior Expert" at CSEM SA (CH)
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Posted: 1 decade ago Jun 25, 2010, 11:09 a.m. EDT
Hi

check the formula used for jomega (scalar variables if I remember right), and check the formulation of the time and harmonic development of the PDE in the doc.

The time derivative is replaced by the -j*w (check the sign convention) where w = omega is 2*pi*f where f is the frequency, it should ring a bell w.r.t. Laplace development as used i.e. in control, no ?

Have fun Comsoling
Ivar
Hi check the formula used for jomega (scalar variables if I remember right), and check the formulation of the time and harmonic development of the PDE in the doc. The time derivative is replaced by the -j*w (check the sign convention) where w = omega is 2*pi*f where f is the frequency, it should ring a bell w.r.t. Laplace development as used i.e. in control, no ? Have fun Comsoling Ivar
Yasaman Daghighi
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Posted: 1 decade ago Jun 29, 2010, 7:24 p.m. EDT
Hello Ivar,
I have one question that think you might know the answer, as I saw you replied many of the questions in Comsol forum. I do appreciate if you can help me out with my problem.


I am trying to model ALE transient system in 3D as I attached the file, I was wondering if you cna help me to find out how can I fix the "shape function" problem with my file.

"s" [as I guess] is the shape function for 2D simulation, but for 3D modeling, I tried the same rules and it face to error.
would you please have a look at my files?
Best and thank you in advance
Yasaman
Hello Ivar, I have one question that think you might know the answer, as I saw you replied many of the questions in Comsol forum. I do appreciate if you can help me out with my problem. I am trying to model ALE transient system in 3D as I attached the file, I was wondering if you cna help me to find out how can I fix the "shape function" problem with my file. "s" [as I guess] is the shape function for 2D simulation, but for 3D modeling, I tried the same rules and it face to error. would you please have a look at my files? Best and thank you in advance Yasaman
Hoypoy's Dad
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Posted: 1 decade ago Apr 13, 2011, 1:05 p.m. EDT
Dear Alessandro,

When simulating the microcantilever beam in water, did you apply the fluid-structure interaction boundary condition only on the top of the beam or on top and bottom? Thanks in advance!

Jin


Hi Teddy,
give a look to the pdf file: FSI Analysis of Microcantilevers Vibrating in Fluid Environment.
You find it in the "Paper & Presentations" section.
All models are in 3D but I think it is quite easy to convert them in 2d. No ale module is employed and all analyses are of "Damped Eigenfrequency" type.
I hope this helps.

Alessandro


Dear Alessandro, When simulating the microcantilever beam in water, did you apply the fluid-structure interaction boundary condition only on the top of the beam or on top and bottom? Thanks in advance! Jin [QUOTE] Hi Teddy, give a look to the pdf file: FSI Analysis of Microcantilevers Vibrating in Fluid Environment. You find it in the "Paper & Presentations" section. All models are in 3D but I think it is quite easy to convert them in 2d. No ale module is employed and all analyses are of "Damped Eigenfrequency" type. I hope this helps. Alessandro [/QUOTE]

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