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VOF modelling open channel river flow

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Old   January 14, 2003, 16:59
Default VOF modelling open channel river flow
Matthew Roberts
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I wish to model 3D turbulent flow and water surface superelevation in open channel meandering rivers. My channel geometry consists of three 180 degree constant radius of curvature bends, rectangular in cross-section. I have split the inlet face in gambit along the air/water interface and in fluent given a vol. fraction 1.0 to phase 2(water) for the water inlet and a vol. fraction 0.0 to phase 2(water) for the air inlet.

Q1: Do I need to patch the initial volume of water/air into the channel(as this is complex) or can I simply let the VOF model determine the liquid/gas interface as the fluid flows through the geometry, since I'm using an unsteady solver?

Q2: When I initialise the entire flow field the options available to provide flow velocities are in the cartesian x,y,z coordinate directions, however this is not applicable when providing an initial guess for the flow around a bend! At present I am simply leaving the velocities as the default zero. Is there a way of specifying a downstream velocity parallel to the channel walls to reduce the convergence time?

Q3: Finally, I have specified the air and water inlets as velocity inlets, is OUTFLOW the best BC for the outlet or should I use PRESSURE OUTLET? Also what about the BC along the upper surface ABOVE the air as I want to ensure its an "open channel", do I specify SYMMETRY of PRESSURE INLET (as detailed in the tutorial guide)?

Any advice would be gratefully appreciated, Cheers Mat
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Old   January 15, 2003, 07:02
Default Re: VOF modelling open channel river flow
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I think it is better to patch your initial condition to have better convergency. also for b.c i think you had better to use pressure inlet with gage equal to zero for your surrounding environmetn feild of water - flow also for outlet.

wish it could help you.......
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Old   January 16, 2003, 14:38
Default Re: VOF modelling open channel river flow
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hi i have a problem like u have please send me if u have more info thanks
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Old   January 20, 2003, 03:18
Default Re: VOF modelling open channel river flow
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dear sir iwant to modelling a recuperator with fluent. i have any problem in it.
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Old   July 15, 2009, 13:50
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Hello dear christine.

I just saw your problem and learned that you got its solution. I have just started my MS and am working in the same field i.e. open channel flows. It would be very nice of you if you could please help me. Feel free to contact me on

With best regards

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Old   July 31, 2009, 11:33
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anissa ghomrassi
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hello i'm also working in sedimentation in meandering rivers please contact me on
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Old   July 31, 2009, 12:52
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Check the help file, as I remember, a pressure BC and an outflow BC should not be used together in one problem.
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