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Fluid flow - solid body rotation coupling problem

Posted 04.01.2014, 10:37 GMT-5 Fluid & Heat, Mesh, Structural Mechanics Version 4.3b 3 Replies

Utku Göreke
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Dear all,

I am working on a 2D model of a turbine subjected to air and to do this I guess I need to use laminar flow and ale. Also solid mechanics to define a free to rotate connection.

What I want to do is, give the air inlet while the turbine is free to rotate and see the turbine rotating under the effect of fluid.

So basically what I did is to define a boundary load on the turbine walls. I used "p" for this which is fluid pressure. Also I used ale to define a sliding mesh for the fluid region which is supposed to be rotating with the turbine. And for the turbine I defined a rigid connector and configured it for free rotation.

But results showed very little displacement (in microns level) for air inlet velocity of 10 m/s. I was expecting much higher displacement for the turbine.

So apparently I'm configuring something wrong or have a missing element in the model I guess. My model is attached below but ı had to delete study due to file size. I appreciate any help. Thanks.

Utku

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3 Replies Last Post 19.02.2015, 18:43 GMT-5
COMSOL Moderator

Hello Utku Göreke

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Mengqi Li
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Posted: 10 years ago 18.02.2015, 14:45 GMT-5
Hi Utku,

I am also working on this kind of simulation, 3D particle immigration in pressure-driven flow.
I downloaded your model and studied it carefully. I think the key point is to find the acting force on the turbine. As you said, the "p" represent the pressure in the liquid, can it equals to the pressure acting on the turbine? I don't know. What do you think? If you have make any progress, could you tell me?

Thank you very much.
Mengqi

Hi Utku, I am also working on this kind of simulation, 3D particle immigration in pressure-driven flow. I downloaded your model and studied it carefully. I think the key point is to find the acting force on the turbine. As you said, the "p" represent the pressure in the liquid, can it equals to the pressure acting on the turbine? I don't know. What do you think? If you have make any progress, could you tell me? Thank you very much. Mengqi
Utku Göreke
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Posted: 10 years ago 19.02.2015, 03:14 GMT-5
Yes pressure difference creates the driving force in this situation and defining it as a boundary load should work in this case. But the problem is as far as I understand sliding mesh works only for small displacements. In my case the displacement of mesh was supposed to be very high wrt step size of the simulation thus it failed.

I could not make any progress on the issue. It is a difficult one. But if you have a case with simpler dynamics, this story can be related to you;
www.comsol.com/story/sea-floor-energy-harvesting-14477
Problem is handled in FSI module by entering the governing equations to the model.

Good luck.
Yes pressure difference creates the driving force in this situation and defining it as a boundary load should work in this case. But the problem is as far as I understand sliding mesh works only for small displacements. In my case the displacement of mesh was supposed to be very high wrt step size of the simulation thus it failed. I could not make any progress on the issue. It is a difficult one. But if you have a case with simpler dynamics, this story can be related to you; http://www.comsol.com/story/sea-floor-energy-harvesting-14477 Problem is handled in FSI module by entering the governing equations to the model. Good luck.
Mengqi Li
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Posted: 10 years ago 19.02.2015, 18:43 GMT-5
Hi Utku,

Thank you for your suggestions. The reason why I choose to use multiphysics rather than FSI is that I have to simulate EOF later. I think using multiphysics is more flexible than a single FSI module.
About the force acting on the rotator, have you read this discussion?
www.comsol.com/community/forums/general/thread/11441/
Integration of "reacf()" or "xx_lm" along the boundary rotator is used to represent the reaction force.
However, about the problem you meet with now, the displacement of mesh can not be very high, I am sorry I do not know how to solve it. Hope you can solve it recently.

Good Luck.
Hi Utku, Thank you for your suggestions. The reason why I choose to use multiphysics rather than FSI is that I have to simulate EOF later. I think using multiphysics is more flexible than a single FSI module. About the force acting on the rotator, have you read this discussion? http://www.comsol.com/community/forums/general/thread/11441/ Integration of "reacf()" or "xx_lm" along the boundary rotator is used to represent the reaction force. However, about the problem you meet with now, the displacement of mesh can not be very high, I am sorry I do not know how to solve it. Hope you can solve it recently. Good Luck.

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