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free surface modelisation

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Old   March 22, 2012, 04:19
Default free surface modelisation
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Dear all,

I am trying to model an open channel flow (free surface flow) in a pipe.
The requirement is to obtain the 3D turbulent structure, including turbulence-driven secondary currents.
I have tried innumerable strategies (combined inlet and seperate inlets....) with no luck in obtaining the expected results.
In CCM+, I have defined a field function to fix the water level at the inlet (and used the same for initialization) but the free surface disapears....

Prob definition:
Physics Models:
-Multiphase VOF
-Segregated Solver
-Turbulent -> K-e realiz
-Unsteady flow (Time step = 0.05s)
BC's:
-Combined Inlet: Velocity inlet [Magnitude = 0.5m/s)]
-Outlet: Pressure Outlet
-Turbulence specifications for Inlets and Outlets:
TI = 10%

Please have a look at the problem set up and sugest any change in strategy .

Thank you
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Old   March 25, 2012, 04:10
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I think separate inlets is the best option, or maybe it will work using the flat wave model for combined inlet.
How does the interface disappear?
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Old   March 25, 2012, 14:36
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Ryan Coe
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Have you applied any control to the water level at the outlet?
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Old   April 1, 2012, 16:59
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The water level at the outlet should be a result of the behaviour within the domain. Anyway, the pressure at the outlet should be set according to the expected water level.
Just a stupid question: Did you switch on gravity? Is the mesh fine enough?
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Old   April 10, 2012, 04:18
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yes i switch on gravity,
i put my air with a velocity of 0.5m/s, the same for water.
I attached a picture of the water level at the end of the simulation. I can't attache my report on the original format, my file exceeds the forum's limit . So i put the screenshots
Attached Images
File Type: jpg water level.jpg (20.6 KB, 34 views)
File Type: jpg report1.jpg (92.5 KB, 30 views)
File Type: jpg report2.jpg (91.8 KB, 18 views)
File Type: jpg report3.jpg (95.1 KB, 15 views)
File Type: jpg report4.jpg (92.8 KB, 10 views)

Last edited by hydraulic; April 10, 2012 at 04:40.
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Old   April 10, 2012, 04:21
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Thanks again,
Attached Images
File Type: jpg report5.jpg (97.3 KB, 9 views)
File Type: jpg report6.jpg (93.3 KB, 5 views)
File Type: jpg report7.jpg (93.9 KB, 5 views)

Last edited by hydraulic; April 10, 2012 at 04:43.
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