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Free Surface Modelling and Reversed Flow Error

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Old   August 10, 2004, 11:43
Default Free Surface Modelling and Reversed Flow Error
  #1
Javier González
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Hi, I'm a new user of Fluent. i'm trying to model a 2d rectangular tank with a free surface. I have read that the VOF model is used for tracking a free-surface, but that is not my case. I have used a pressure outlet boundary condition in the top of the tank, but an error appears showing that there is reversed flow in a given number of faces. I have read that the apropriate boundary condition to be used is a symetry boundary.

Does Anyone know why, and if is this correct?

Thanks in advance Javier
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Old   August 11, 2004, 07:23
Default Re: Free Surface Modelling and Reversed Flow Error
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Raphael
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What type of flow are you modelising? Where are the inlet and the outlet? I am currently doing the same (tank, VOF..) with a velocity inlet and a pressure outlet for the vertical sides, and symmetry for the top and the bottom. It works, so I could help you if it was the same...

Raphael
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Old   August 11, 2004, 15:30
Default Re: Free Surface Modelling and Reversed Flow Error
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Javier González
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The inlets and aoutlets are microjets placed at the bottom. The top of the tank is the free surface. I try the symetry boundary at the top and it works good, but i will try with VOF to see how it is altered.

Thanks for your help, and feel free to email me for anything related to the modelation.

Best regards. Javier
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Old   August 13, 2004, 12:53
Default Re: Free Surface Modelling and Reversed Flow Error
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Raphael
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Have you ticked the box "specified operating density" in the operating conditions panel? I had problems with hydrostatic pressure in the light phase, above the surface, with important pressure variations, and a disturbace of the flow. As soon as I ticked this box, problems were solved, and hydrostatic pressure was OK.

Hope this helps.

Raphael
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Old   August 16, 2004, 11:37
Default Re: Free Surface Modelling and Reversed Flow Error
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Javier González
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Yes, I have done that, But now appears another error when i'm running the VOF. It says:

"Turbulent Viscosity limited to turbulent viscosity ratio of 1.000000e+05 in 8 cells"

In the plot of the residuals one can see how the grow in time (not all, but someones).

I had to change the pressure inlet zone type for the upper boundary to a symmetry boundary to avoid the reversed flow error. I have reduced the under-relaxation factors for al ecuations. But I can't control the break down of the model.

Best Regards, Javier.

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