# Open Channel Flow

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 March 13, 2011, 16:36 Open Channel Flow #1 New Member   Join Date: Mar 2011 Posts: 3 Rep Power: 15 Hi, I'm currently trying to perform a simple open channel flow simulation using Fluent 6.3.26 and having absolutely no luck. I've tried looking for tutorials online but haven't found any worth mentioning as they don't cover what I'm trying to do. The current problem I'm trying to solve is a simple geometry as follows: http://i.imgur.com/HQ5NZ.jpg (Link to well known image hosting website) The picture shows what I expect the results to be and the boundary conditions that I've set. The length of the model is 2 meters and the height is 0.5 meters. The aim I'm trying to achieve with this simulation is just to get a working open channel flow example. Starting from opening Fluent, these are the steps I would expect to take: ------------------------------------- (Read case) Define -> Operation ConditionsTick: gravity -> Y = -9.81Define -> Models -> MultiphaseVolume of Fluid -> Tick: Open Channel Flow (Implicit)Define -> MaterialsDefine WaterDefine -> Phasesphase-1: primary-phase -> airphase-2: primary-phase -> waterDefine -> Boundary Conditions:Inlet: mass-flow-inletMixture: Multiphase -> Tick: Open ChannelFree Surface Level = 0.2Bottom Level = 0.1air: Momentum -> Mass Flow-Rate = 1kg/swater: Momentum -> Mass Flow-Rate = 100kg/sOutlet: pressure-outletMixture: Multiphase -> Tick: Open ChannelFree Surface Level = 0.1Bottom Level = 0Solve -> Initialize -> Init Solve -> Iterate (1000 iterations) ------------------------------------- I've also tried, unsteady flow, different flow rates including zero for both air and water, ticking or unticking open channel flow at the outlet, and adding various turbulence models. Though if you think these to be the problem, please say, as I may have been adding half the right things but missing out crucial components. I have also tried different mesh densities (9,000 elements to 255,000 elements) The current results I attain show a contour phase plot of all air. My question is simply, what have I done wrong? I have been trying to follow the open channel flow user guide notes from Fluent, and (I think) done everything they say, but still get spurious results. Thanks in advance.

 March 13, 2011, 23:56 #2 Member   Join Date: Apr 2009 Location: Pune Posts: 37 Rep Power: 17 I presume you are simulating it in 2D. what fluid heights you have mentioned at the inlet and outlet locations..?

 March 14, 2011, 03:45 #3 New Member   Join Date: Mar 2011 Posts: 3 Rep Power: 15 Thanks very much for the reply! My apologies, yes it's 2D. I've set the fluid heights at 0.1m at the inlet and outlet. Does this significantly change the motion of the fluid downstream? At the inlet it would make a difference but I fail to see what setting a height of 0.1m at the outlet achieves.

 August 19, 2011, 14:21 #4 Member     Omid Seyedashraf Join Date: May 2010 Posts: 49 Rep Power: 16 air: Momentum -> Mass Flow-Rate = 0.0001kg/s also you have patched the water section , or not mentioned here you had to define water in adapt=> region => mark and close after the initialization, patch the marked section

 February 25, 2015, 16:26 #5 Member   azna Join Date: Nov 2012 Posts: 30 Rep Power: 13 how did you patched the water section for this ? for region that is not rectangular. for example trapezoidal

 Tags fluent 6.3.26, open channel, open channel flow