# interFoam, problems with volume fraction conservation

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 October 12, 2009, 03:58 interFoam, problems with volume fraction conservation #1 New Member   jhegar Join Date: Jun 2009 Posts: 4 Rep Power: 10 Hello everybody! I´m having problems with interFoam solver used in the new OpenFoam version 1.6. From the first time step the liquid volum fraction starts to decrease, and that shouldn´t happen in my problem, until the water reachs the Outlet (that happens after 3-4 seconds of simulation). With the same boundary conditions I obtained no problem with version 1.5. The liquid volume fraction was constant till the liquid come to the Outlet. It seems like if there is somewhere some type of numeric problem. My problem is a U-pipe that has enough water to full fill the horizontal part of the pipe. Can someone help me with this tema? Do anyone know if they have change something by the numeric procedure of the new version? Thank you very much for your help and time.

 October 12, 2009, 07:32 #2 Member   Jean-Peer Lorenz Join Date: Mar 2009 Location: Rostock, Germany Posts: 33 Rep Power: 10 Hi, I do not understand your setup exactly. Could you provide some additional information about the case? Maybe a picture of the domain? I guess the amount of water remains equal while it moves towards to outlet? Regards. Jean-Peer

 October 12, 2009, 07:51 #3 New Member   jhegar Join Date: Jun 2009 Posts: 4 Rep Power: 10 U_pipe.JPGHi, hear I attach a picture with the geometry boundaries of the problem. Thanks.

 October 13, 2009, 04:18 #4 Senior Member   Niels Gjoel Jacobsen Join Date: Mar 2009 Location: Deltares, Delft, The Netherlands Posts: 1,759 Rep Power: 29 Hi I have read somewhere on the Forum that chaging from pd -> p makes the zeroGradient on p at walls erroneous, as you have a hydrostatic component, i.e. dp/dn differs from zero. I am currently working in 1.6, hence could you see, if you can compute the hydrostatic pressure with no inflow in your setup without loosing any fluid? Hope it helps, Niels

 October 15, 2009, 06:53 interFoam no volume conservation in 1.6 #5 New Member   Harald Swidersky Join Date: Oct 2009 Location: Munich, Germany Posts: 1 Rep Power: 0 Hello, With Version 1.6 I observed also, that the volume fraction of liquid drops if I calculate a half filled bending over a longer time (4-10 s) until the liquid dissapeared completely. At the open ends of the bending I set u=0 m/s and P = 10e5 Pa respectively (-> zero flow). The hydrostatic pressure seems to be o.k.. The violation of the volume conservation does not appear if I use version 1.5 ! I would be glad, if someone knows what has been changed in the underlying solver or equations since 1.5.

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