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September 15, 2010, 19:24 |
OpenFOAM 1.7.1: Oscillating CFL number
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#1 |
Member
Lars Kiewidt
Join Date: Sep 2009
Location: Germany
Posts: 54
Rep Power: 16 |
Hi,
I want to simulate the capillary rise of a fluid in a closed rectangular container in a low-gravity environement using interFoam in OpenFOAM 1.7.1. So, I have only walls and symmetryPlanes as BCs. The container has a square cross section with length 1 cm and a height of 10 cm. The contact angle of the fluid is 0°. Here are the BCs (symmetryPlane is of course of type symmetryPlane): Code:
alpha1: walls { type constantAlphaContactAngle; theta0 0; limit gradient; value uniform 0; } p_rgh: walls { type fixedFluxPressure; adjoint no; } U: walls { type fixedValue; value uniform (0 0 0); } So is there someone else, who has had the same problems or who can help me? Thanks in advance! Lars |
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September 17, 2010, 02:07 |
OpenFOAM 1.7.1: Oscillating CFL number
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#2 |
Senior Member
ata kamyabi
Join Date: Aug 2009
Location: Kerman
Posts: 323
Rep Power: 17 |
Hi Lars
Did you examine your case with bigger contact angles? Best regards Good luck Ata |
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September 17, 2010, 09:40 |
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#3 |
Member
Lars Kiewidt
Join Date: Sep 2009
Location: Germany
Posts: 54
Rep Power: 16 |
Thanks for your answer.
No, I didn't, yet. But maybe it's a good idea. For now I tried to use a more viscous fluid to reduce the dynamics of the rise. I read some papers about CFD (VOF) and contact angles. Is there any documentation how interFoam deals with the singularity of the no-slip BC? Lars |
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September 18, 2010, 01:50 |
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#4 |
Senior Member
ata kamyabi
Join Date: Aug 2009
Location: Kerman
Posts: 323
Rep Power: 17 |
Hi Lars
How are you? I hope you are doing very well. What you mean "singularity of the no-slip BC"? You can see the PhD thesis of Onno Ubbink entitled by: "Numerical prediction of two fluid systems with sharp interfaces" I hope that help you. Best regards Ata |
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September 18, 2010, 03:55 |
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#5 |
Member
Lars Kiewidt
Join Date: Sep 2009
Location: Germany
Posts: 54
Rep Power: 16 |
So, I tried OpenFOAM-1.6 and it's performs stable but the results are not really good. 40 to 50 % error to the analytical comparison. I think, I have to work on the mesh and on the time step to get some higher accuracy. OpenFOAM-1.7.1 still crashes after a while. I don't think it's a bug, it is only because of the special case.
Now to the singulartiy and the no-slip condition. Usually the velocity at the wall should be zero but the fluid has to move anlong the wall in order to wet the surface. I read about an aproach of disabling the no-slip BC and replace it by a no-friction BC. The pressure loss is then compensated by an artificial body force. The intensity of the body force is unfortenatly a fit parameter and depends on the case. By the way, I have the PhD thesis of Ubing and the one of Rusche, but I didn't get too much into it, yet. I think it will be worth doing so. Thank you for your help! But I still wonder why OF-1.7.1 has so many problems with this case while it is working with the former version!? Lars |
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