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Matthew Roberts January 14, 2003 16:59

VOF modelling open channel river flow

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

heydari January 15, 2003 07:02

Re: VOF modelling open channel river flow
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.......

varshavian January 16, 2003 14:38

Re: VOF modelling open channel river flow
hi i have a problem like u have please send me if u have more info thanks

morteza January 20, 2003 03:18

Re: VOF modelling open channel river flow
dear sir iwant to modelling a recuperator with fluent. i have any problem in it.

mechovator July 15, 2009 13:50

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


anissa July 31, 2009 11:33

hello i'm also working in sedimentation in meandering rivers please contact me on

John July 31, 2009 12:52

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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