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Fluid-Structure Interaction

Posted Mar 15, 2011, 5:33 p.m. EDT 6 Replies

Pranav Ashtaputre
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Hi,
There is a sample Fluid-Structure interaction problem given in Comsol model library.
In this module, is it possible to specify the deflection of cantilever in terms of relation between y and x, y being the deflection and x the length co-ordinate of beam so as to model the coupling?
I obtained this relation using structural part separately. I want to input this relation of x and y to the FSI module to solve for the fluid.

Thanks
Pranav
6 Replies Last Post Nov 20, 2012, 1:37 a.m. EST
Ivar KJELBERG COMSOL Multiphysics(r) fan, retired, former "Senior Expert" at CSEM SA (CH)
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Posted: 1 decade ago Mar 15, 2011, 7:00 p.m. EDT
Hi

I'm not sure I understand you correctly, as the FSI is solving the bi-directional coupled structure - fluid interaction.

But you can always add a prescribed displacement on the structure, but it might make the solution rather stiff, worth to try

--
Good luck
Ivar
Hi I'm not sure I understand you correctly, as the FSI is solving the bi-directional coupled structure - fluid interaction. But you can always add a prescribed displacement on the structure, but it might make the solution rather stiff, worth to try -- Good luck Ivar
Pranav Ashtaputre
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Posted: 1 decade ago Mar 16, 2011, 2:32 p.m. EDT
Hi,
I know FSI solves coupled problem. However, if I want to input deflection of beam(relation between x and y) at initial time step and use this deflection for obtaining fluid pressure due to the deformed shape of the beam, this could be a way to model the coupling.

My question is if I can use FSI for getting fluid pressure due to deformed shape?


Thanks
Pranav
Hi, I know FSI solves coupled problem. However, if I want to input deflection of beam(relation between x and y) at initial time step and use this deflection for obtaining fluid pressure due to the deformed shape of the beam, this could be a way to model the coupling. My question is if I can use FSI for getting fluid pressure due to deformed shape? Thanks Pranav
Mychal Smith
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Posted: 1 decade ago Jun 22, 2012, 1:59 p.m. EDT
Did you ever get an answer to your question. I'm experiencing a similar problem.
Did you ever get an answer to your question. I'm experiencing a similar problem.
Mustafa Abd El-Mageed
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Posted: 1 decade ago Nov 19, 2012, 4:36 p.m. EST
Dear Ivar ;
About the tutorial of FSI (beam in water) it uses micro dimensions , when I increase the dimensions to macro scale an error massage appears "nonlinear solver didn't converge " else if increase the meshing . I tried to disable the inertial term , really it works but I'm using water at speed 15 cm/s and beam 10 cm length so inertia is an important thing .
so if any solutions

thanks a lot
Dear Ivar ; About the tutorial of FSI (beam in water) it uses micro dimensions , when I increase the dimensions to macro scale an error massage appears "nonlinear solver didn't converge " else if increase the meshing . I tried to disable the inertial term , really it works but I'm using water at speed 15 cm/s and beam 10 cm length so inertia is an important thing . so if any solutions thanks a lot
Ivar KJELBERG COMSOL Multiphysics(r) fan, retired, former "Senior Expert" at CSEM SA (CH)
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Posted: 1 decade ago Nov 20, 2012, 1:34 a.m. EST
Hi

If you have a closed fluid volume with a structure around, indeed if you defome one sode you will see a pressure increase ported to all the other boundaries by the fluid

--
Good luck
Ivar
Hi If you have a closed fluid volume with a structure around, indeed if you defome one sode you will see a pressure increase ported to all the other boundaries by the fluid -- Good luck Ivar
Ivar KJELBERG COMSOL Multiphysics(r) fan, retired, former "Senior Expert" at CSEM SA (CH)
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Posted: 1 decade ago Nov 20, 2012, 1:37 a.m. EST
Hi

Changing the scale might change some of the parameters used for the convergence geuesses. If it solves with disabled inertal terms, it's telling you that the transinet at "initial conditions" due to the 2nd derivative are rather large. The different physics laws scale differently with the model volume and surface, soI'm not astonished that you can get convergence errors.

Probably the easiest is to define the initial steady state situation, run a stationary case to get the model into this state, and tehn run a temporal solver using the steady state conditions as starting point. Not sure it can be done without matlab in 3.5, cannot remember, its rather standard in the v4 solver sequnce

--
Good luck
Ivar
Hi Changing the scale might change some of the parameters used for the convergence geuesses. If it solves with disabled inertal terms, it's telling you that the transinet at "initial conditions" due to the 2nd derivative are rather large. The different physics laws scale differently with the model volume and surface, soI'm not astonished that you can get convergence errors. Probably the easiest is to define the initial steady state situation, run a stationary case to get the model into this state, and tehn run a temporal solver using the steady state conditions as starting point. Not sure it can be done without matlab in 3.5, cannot remember, its rather standard in the v4 solver sequnce -- Good luck Ivar

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