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June 14, 2017, 04:47 |
BC for outlet - interFoam - spillway
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#1 |
New Member
Kim Le
Join Date: May 2016
Location: Lyon, France
Posts: 21
Rep Power: 10 |
Hello everyone !
I am working on OpenFOAM 4.1 and I am using interFoam to model a lateral spillway with two exits. See the attached image. https://drive.google.com/open?id=0B7...TdiekNuNjB1emM I have tried many set of BC for my outlets. Please see the excel chart. Some words are in French but it is quite explicit. https://drive.google.com/open?id=0B7...lJiNXc4MmlLSjQ I am struggling with the fact that : - either the simulation is doing well but one outlet is not emptying, or the two outlets are have very, very small outflow (such as 0.02 m3/s) - either the chamber seems to empty in both outlets but it encounters some diverging problem. I am monitoring U and P with fieldMinMax in controlDict and it shows exploding values ! checkMesh does not seem to report anything wrong. I have tried so many combinations of BC for the outlets that I am starting to wonder if it doesn't come from my mesh. Please, can anyone help ? I have been working on this case for three months now. |
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June 14, 2017, 05:20 |
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#2 |
Senior Member
Uwe Pilz
Join Date: Feb 2017
Location: Leipzig, Germany
Posts: 744
Rep Power: 15 |
I recommend setting zero gradient for U and a fixed pressure for p at the outlets. I did not find this combination in your sheet. But it may be I missed something.
For the inlet a fixed U (which you want to simulate) and zero gradient for the pressure. That means: The outflow is "free", without any constraints. The pressure level has to set somewhere, and the outlet is fine for this. The inflow is also free: It is not (additional) pressure driven.
__________________
Uwe Pilz -- Die der Hauptbewegung überlagerte Schwankungsbewegung ist in ihren Einzelheiten so hoffnungslos kompliziert, daß ihre theoretische Berechnung aussichtslos erscheint. (Hermann Schlichting, 1950) |
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June 14, 2017, 06:54 |
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#3 |
New Member
Kim Le
Join Date: May 2016
Location: Lyon, France
Posts: 21
Rep Power: 10 |
Thanks for your reply Uwe.
But isn't it the case for the first try "0" I made ? From the .H file, I understood that pressureInletOutletVelocity means that zeroGradient is applied for all components on U when there is an outflow. I am going to try your solution anyway. For the outlet, should I use totalPressure with p0 = 0 ? Or fixedValue = 0 ? I hope this time, it will work ! Plus, I am also wondering if it comes from my initial conditions. I used for the last cases, solution that seems correct for the initial conditions using mapFields. The fact that it is not emptying or diverging cannot come from that, can it ? I don't know if should use a simple setFields and initialize with a simple box of water on the top with a small velocity. I suppose this would take more time to converge than using mapFields. |
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June 14, 2017, 09:03 |
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#4 |
Senior Member
Uwe Pilz
Join Date: Feb 2017
Location: Leipzig, Germany
Posts: 744
Rep Power: 15 |
> pressureInletOutletVelocity means that zeroGradient
I don't work with pressureInletOutletVelocity , but always use zeroGradient. > use totalPressure with p0 = 0 ? Or fixedValue = 0 ? I always use fixedValue.
__________________
Uwe Pilz -- Die der Hauptbewegung überlagerte Schwankungsbewegung ist in ihren Einzelheiten so hoffnungslos kompliziert, daß ihre theoretische Berechnung aussichtslos erscheint. (Hermann Schlichting, 1950) |
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