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Setting BCs for Riverine Flows using Interfoam |
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#21 | |
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ali naqi mohammadi
Join Date: Dec 2012
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Quote:
walls { type nutkRoughWallFunction; value uniform 0; Ks uniform .0014; Cs uniform .5; } |
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#22 |
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Benjamin
Join Date: Apr 2014
Location: Zürich
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Hey all,
I'm working at a similar problem at the moment and hope anyone could help me. I have a free surface flow channel with a narrowing. Like before I want to give the inlet velocity (here 0.5 m/s), but I need to give a predefined outlet-pressure somehow (because I need to be able to calculate for a given water elevation at the outlet). I thought I couldn't define a pressure for the whole outlet, so I chose to define it only at the bottom of the river bed (over the last m of the channel before the outlet). The idea was to be able to give a certain hydrostatic pressure at the ground, which should define the water level.
![]() Casefiles (currently negative x-axis, to avoid the problem of reflecting -.-): Thanks and have a nice WE, Benji |
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#23 |
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ali naqi mohammadi
Join Date: Dec 2012
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for implementation of fixed depth at outlet, first you should divide the mesh block into two blocks: one with height of the outlet depth and the other for air.
so we will have two outlet: waterOutlet and airOutlet. zeroGradient boundary condition for waterOutlet . atmosphere boundary condition for airOutlet. |
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#24 |
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Albrecht vBoetticher
Join Date: Aug 2010
Location: Zürich, Swizerland
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Hi Benji,
have you tried just outlet { type buoyantPressure; value uniform 0; } for p_rgh ? |
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#25 | |
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Antonio
Join Date: Jan 2013
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Hi Benji,
Have you tried Kflora suggestion. I have used in some steady open flows succesfully. I would suggest to enlarge the end of the channel to reduce influence of using a uniform 1D velocity profile. Her suggestion is to use a fixed velocity bc of water flow rate input/ water depth aim. Being it applied to all the outlet surface (water and air) Quote:
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#26 |
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Fatemeh
Join Date: Dec 2015
Location: Isfahan,Iran
Posts: 39
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Hi every one!
I have a similar problem. I have a 3D open channel which has a curved route. I want to enter a fully developed flow in the inlet and don't know how it will be at the outlet. can any one tell me what are the right boundary conditions for inlet, outlet and free surface? thanks a lot. |
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#27 | |
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Bashar
Join Date: Jul 2015
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I am facing similar issues, I am working of flow past plate . Did you mamnge to make this work for you ? |
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#28 |
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Fatemeh
Join Date: Dec 2015
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#29 | |
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Bashar
Join Date: Jul 2015
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Quote:
Thanks a lot for the info.Will be ok for you to share the case file ? But thanks anyway,I will try your BC.I am using single inlet patch,I saw some cases where they use two separate inlet patches,one for air and the other for water. Did you use single inlet? Thanks Sent from my iPhone using CFD Online Forum mobile app Last edited by Bashar; February 14, 2017 at 13:35. |
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#30 | |
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Fatemeh
Join Date: Dec 2015
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#31 |
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Bashar
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#32 | |
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Bashar
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Also, what setting should alpha.water get, i.e. BC. Bashar Last edited by Bashar; February 22, 2017 at 10:00. |
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#33 |
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Jeff DeGraff
Join Date: Apr 2018
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An old post with a lot of good information.
I am modeling a river and would like to know if there are any additional tips on setting the downstream flow depth. I used Kflora's work around for simple rectangular channels but would like to know if there are work arounds for irregular shapes. Last edited by jdegraff; September 13, 2018 at 08:23. Reason: Wrong title |
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#34 |
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Honza Höll
Join Date: Mar 2016
Location: Brno, CZ
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Maybe a good option is to make river a little bit longer (to the point where results from new cross section dont influence results in the initial location of downstream BC) and there use regular shape.
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#35 |
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Jeff DeGraff
Join Date: Apr 2018
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indy07cz - Good suggestion. That worked for most cases.
Now what I am finding is that there isn't a constant inlet flow. I tried setting the inlet alpha to 0 (all water) but found that I still get "separation" in the stream. Does anyone have any suggestions? |
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#36 | |
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Jeff DeGraff
Join Date: Apr 2018
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Quote:
Again, if there is a better way of defining boundary "open channel flow" boundary conditions, please let me know. I feel that there is a lot of Foamers that deal with this issue. |
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#37 |
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Albrecht vBoetticher
Join Date: Aug 2010
Location: Zürich, Swizerland
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In case you are using atmosphere boundary conditions for the top, make sure the water does not contact it. Single drops are OK but interFoam can't handle the water/air density difference at the atmospheric boundary condition.
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#38 | |
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Albrecht vBoetticher
Join Date: Aug 2010
Location: Zürich, Swizerland
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Quote:
By the way, I use fixedFluxPressure with complex inlet geometries, combined with fixedValue at the inlet and inletOutlet at the outlet for U. For the atmospheric top I use totalPressure with the corresponding settings and pressureInletOutletVelocity. It works well for mountain torrents |
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#39 | |
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Mahmoud
Join Date: Nov 2020
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Tags |
interfoam, openfoam, river, vof |
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