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

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

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

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

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.