Menu

Discussion Forum

New Discussion
Filter

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 The information provided may be out of date.

Discussion Closed This discussion was created more than 6 months ago and has been closed. To start a new discussion with a link back to this one, click here.

cantilever frequency response in a fluid

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

Teddy Maillot
Send Private Message Flag post as spam

Please login with a confirmed email address before reporting spam

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
Send Private Message Flag post as spam

Please login with a confirmed email address before reporting spam

Posted: 2 decades 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
Send Private Message Flag post as spam

Please login with a confirmed email address before reporting spam

Posted: 2 decades 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
Send Private Message Flag post as spam

Please login with a confirmed email address before reporting spam

Posted: 2 decades 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)
Send Private Message Flag post as spam

Please login with a confirmed email address before reporting spam

Posted: 2 decades 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
Send Private Message Flag post as spam

Please login with a confirmed email address before reporting spam

Posted: 2 decades 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
Send Private Message Flag post as spam

Please login with a confirmed email address before reporting spam

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]

Note that while COMSOL employees may participate in the discussion forum, COMSOL® software users who are on-subscription should submit their questions via the Support Center for a more comprehensive response from the Technical Support team.

Suggested Content