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 The information provided may be out of date.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.

fsi of membrane in water

Posted Mar 12, 2012, 11:40 a.m. EDT Fluid & Heat Version 4.2a 5 Replies

Jaap Verheggen
Send Private Message Flag post as spam

Please login with a confirmed email address before reporting spam

I'm trying to simulate something very simple, a reservoir with a moving wall and the resulting fluif flow.
I think I have set up the simulation correctly, but I get the following error:

Cannot evaluate expression.
Failed to evaluate variable.
- Variable: mod1.u_fluid
- Geometry: 1
- Domain: 2
Failed to evaluate expression.
- Expression: mod1.u_fluid
- Plot: arws1 (Arrow surface)

The problem is that domain 2 is the solid and there shouldn't be any u_fluid to be evaluated there.

Any help is much appreciated, I've included the model.

Cheers.

Attachments:

5 Replies Last Post Apr 5, 2012, 10:30 a.m. EDT
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: 1 decade ago Mar 13, 2012, 3:29 a.m. EDT
Hi

not sure why, but when I remake it (in my 4.2a it works OK, but you should turn of the "include inertial terms for the Solid" and use quasi static to avoid the transients at the start, as well as the self oscilaltory terms, in this way you neglect the (rho*d^2_u_/dt^2) terms

--
Good luck
Ivar
Hi not sure why, but when I remake it (in my 4.2a it works OK, but you should turn of the "include inertial terms for the Solid" and use quasi static to avoid the transients at the start, as well as the self oscilaltory terms, in this way you neglect the (rho*d^2_u_/dt^2) terms -- Good luck Ivar

Attachments:

Jaap Verheggen
Send Private Message Flag post as spam

Please login with a confirmed email address before reporting spam

Posted: 1 decade ago Mar 13, 2012, 5:17 a.m. EDT
You are right, I just rebuild it myself from scratch using the same settings and it's working. I must have changed something inadvertently.
Thanks for checking I'm not going crazy just yet.

You are right, I just rebuild it myself from scratch using the same settings and it's working. I must have changed something inadvertently. Thanks for checking I'm not going crazy just yet.
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: 1 decade ago Mar 13, 2012, 7:51 a.m. EDT
Hi

one thing I forgot to note down in previous message, you where in meters scale and not [um] that has probably also something to do with the issue, the force was somewhat small ;)
Scaling again 1:1'000'000 linear scaling is too much for good precision on solving models even with double floating today, when are the 256 bit floating point processors coming ?

--
Good luck
Ivar
Hi one thing I forgot to note down in previous message, you where in meters scale and not [um] that has probably also something to do with the issue, the force was somewhat small ;) Scaling again 1:1'000'000 linear scaling is too much for good precision on solving models even with double floating today, when are the 256 bit floating point processors coming ? -- Good luck Ivar
Ishan Khan
Send Private Message Flag post as spam

Please login with a confirmed email address before reporting spam

Posted: 1 decade ago Apr 3, 2012, 4:39 p.m. EDT

Hi

not sure why, but when I remake it (in my 4.2a it works OK, but you should turn of the "include inertial terms for the Solid" and use quasi static to avoid the transients at the start, as well as the self oscilaltory terms, in this way you neglect the (rho*d^2_u_/dt^2) terms

--
Good luck
Ivar


Dear Sir

I am running into the same type of error and cannot figure out how to use "quasi static" initially. I have attached the model. Its a 2D FSI where the fluid is pushing the viscoelastic cell . Please suggest
Thank you
Ishan
[QUOTE] Hi not sure why, but when I remake it (in my 4.2a it works OK, but you should turn of the "include inertial terms for the Solid" and use quasi static to avoid the transients at the start, as well as the self oscilaltory terms, in this way you neglect the (rho*d^2_u_/dt^2) terms -- Good luck Ivar [/QUOTE] Dear Sir I am running into the same type of error and cannot figure out how to use "quasi static" initially. I have attached the model. Its a 2D FSI where the fluid is pushing the viscoelastic cell . Please suggest Thank you Ishan

Attachments:

Jaap Verheggen
Send Private Message Flag post as spam

Please login with a confirmed email address before reporting spam

Posted: 1 decade ago Apr 5, 2012, 10:30 a.m. EDT
Your idea is similar to the Fluid-Structure Interaction model. So I suggest you check that one first.
Your idea is similar to the Fluid-Structure Interaction model. So I suggest you check that one first.

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