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Shear stress boundary condition

Posted 19 sept. 2014, 15:51 UTC−4 Fluid & Heat, Computational Fluid Dynamics (CFD) Version 4.1, Version 4.2, Version 4.2a, Version 4.3, Version 4.3a, Version 4.3b, Version 4.4 5 Replies

Aureole
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Hi,

I am trying to solve a simple fluid flow problem. It involves marangoni effect. But, I want to make it simple and apply shear stress as the boundary condition, instead of solving coupled thermal and fluid flow problem.

Here is the problem setup in 2D:
A semi circular surface. Straight edge is fixed. Circular curved surface has shear stress applied on it (Marangoni effect). Center of the curved surface has 0 shear stress, it goes to a maximum near the edge where it meets the straight surface. So I am modeling half of the semicircle with a symmetry boundary condition. Please see the figure attached.

With these stresses applied, I should observe a double circular flow as shown in figure. But instead I am getting something else. I have used "boundary stress" and "general stress". Did I do anything wrong? Is there a way to apply u.n=0 on the curved boundary surface and also apply the stress?

Any help would be greatly appreciated. Thanks in advance.

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5 Replies Last Post 28 avr. 2015, 13:52 UTC−4
Jeff Hiller COMSOL Employee

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Posted: 1 decade ago 19 sept. 2014, 16:47 UTC−4
Hi there,
The plot that shows what you expect to see does not display symmetry about the vertical axis. Under those circumstances, it should not be surprising that you get a different result in a COMSOL model that presumes symmetry.
I hope this helps.
Jeff
Hi there, The plot that shows what you expect to see does not display symmetry about the vertical axis. Under those circumstances, it should not be surprising that you get a different result in a COMSOL model that presumes symmetry. I hope this helps. Jeff
Aureole
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Posted: 1 decade ago 19 sept. 2014, 17:18 UTC−4
Thanks Jeff. The attached plot is from the actual system, that's why it is little off from symmetry. But, I was the COMSOL solution should show symmetry. But what I am wondering is, why it is completely off, and not showing any circular flow at all.

Any suggestions as to how to implement u.n=0 on the curved boundary surface will be very helpful.

Thanks
Thanks Jeff. The attached plot is from the actual system, that's why it is little off from symmetry. But, I was the COMSOL solution should show symmetry. But what I am wondering is, why it is completely off, and not showing any circular flow at all. Any suggestions as to how to implement u.n=0 on the curved boundary surface will be very helpful. Thanks
Jeff Hiller COMSOL Employee

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Posted: 1 decade ago 19 sept. 2014, 17:34 UTC−4
Please post your .mph file if you would like other Discussion Forum users to be able to provide feedback. Otherwise we can only make guesses.
Jeff
Please post your .mph file if you would like other Discussion Forum users to be able to provide feedback. Otherwise we can only make guesses. Jeff
Aureole
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Posted: 1 decade ago 22 sept. 2014, 11:58 UTC−4
Here is the .mph file.
Here is the .mph file.

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Tapan Pradhan
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Posted: 10 years ago 28 avr. 2015, 13:52 UTC−4
I am also facing the same problem. I want to use the boundary condition : const 1 (del u/del s)= const2 (del T/del s) at the interface. Here, u and T are velocity and temperature. s is the tangential direction. Can you please give some idea to use this boundary condition in comsol?
I am also facing the same problem. I want to use the boundary condition : const 1 (del u/del s)= const2 (del T/del s) at the interface. Here, u and T are velocity and temperature. s is the tangential direction. Can you please give some idea to use this boundary condition in comsol?

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