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fsi of membrane in water

Posted 12 mars 2012, 11:40 UTC−4 Fluid & Heat Version 4.2a 5 Replies

Jaap Verheggen
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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.

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5 Replies Last Post 5 avr. 2012, 10:30 UTC−4
Ivar KJELBERG COMSOL Multiphysics(r) fan, retired, former "Senior Expert" at CSEM SA (CH)
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Posted: 1 decade ago 13 mars 2012, 03:29 UTC−4
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

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Jaap Verheggen
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Posted: 1 decade ago 13 mars 2012, 05:17 UTC−4
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)
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Posted: 1 decade ago 13 mars 2012, 07:51 UTC−4
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
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Posted: 1 decade ago 3 avr. 2012, 16:39 UTC−4

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

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Jaap Verheggen
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Posted: 1 decade ago 5 avr. 2012, 10:30 UTC−4
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.

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