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June 28, 2013, 03:51 |
reversed flow
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#1 |
Member
steven
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hello everyone,
my cas is a 'T' tube connected by two cylindres with an inlet and 2 outlet. the fluide is turbulent. i made the boundary condition as 'outflow', the warning came to me was "reversed flow". i looked for the former thread, it is said that i could change it to 'pressure outlet'. after operation, the warning is always "reversed flow". does someone know what happened? thank you steven |
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June 28, 2013, 06:33 |
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#2 |
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Maxime Perelli
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you have a vortex crossing the outlet.
It is just a warning, let iterate, the warning may disappear
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June 28, 2013, 06:36 |
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#3 |
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allan thomson
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Extend your computational domain at the outlets, i.e. ensure that the outlet is far away from the tee
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June 28, 2013, 07:46 |
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#4 |
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steven
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Ok, thank you, i will wait a bit.
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June 28, 2013, 07:48 |
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#5 |
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steven
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June 28, 2013, 07:54 |
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#6 | |
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steven
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Quote:
https://www.dropbox.com/s/30deqc29eq...ed%20flow.docx |
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June 28, 2013, 08:44 |
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#7 | |
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Maxime Perelli
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Quote:
-check Mesh -how are your turbulent bc?
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June 28, 2013, 08:58 |
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#8 | |
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steven
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Quote:
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June 28, 2013, 09:19 |
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#9 |
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Maxime Perelli
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-what is the quality of worst element? (show worst element option in gambit)
-what are the tubulent bc at your inlet (you showed the turbulent model) -did you scaled your model? -can you copy and paste the output from checkMesh
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June 28, 2013, 09:46 |
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#10 | |
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steven
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Quote:
https://www.dropbox.com/s/xml8ctvagskchbf/0628-2.docx Mesh Quality: Orthogonal Quality ranges from 0 to 1, where values close to 0 correspond to low quality. Minimum Orthogonal Quality = 2.75142e-01 Maximum Aspect Ratio = 1.61014e+01 |
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June 28, 2013, 09:50 |
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#11 |
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Maxime Perelli
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ok, your mesh is ok and seems to be scaled
in the velocity BC, you should have turbulent parameters, waht do you have? How is you material? density, viscosity?
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June 28, 2013, 10:01 |
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#12 |
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steven
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i have the parameters of K and epsilon. k=0.053985 and epsilon=1.4722. the velocity is 5m/s, it is calculated with the Re=100000. the material is water-liquid. density is about 1000kg/m3, and viscosity is about 0.001kg/m-s
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June 28, 2013, 10:15 |
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#13 |
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Maxime Perelli
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Ok I have to hurry
Try to switch with realizable-kepsilon Try with and without enhanced wall treatment
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June 28, 2013, 10:21 |
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#14 |
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steven
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sorry, i didn't understand what you mean 'realizable-kepsilon'. the k,epsilon values that i used are also calculated with Re=100000.
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June 28, 2013, 10:43 |
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#15 |
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Maxime Perelli
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Other turbulence model
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July 2, 2013, 03:33 |
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#16 |
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steven
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July 2, 2013, 05:12 |
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#17 |
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rayan
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Hi,
I have same problem and I think it is the boundary conditions imposed on your two outputs which poses the problem .. when you have two output can not impose "pressure" at outlet.. What are your boundary conditions at the outlets?? |
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July 2, 2013, 05:24 |
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#18 |
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steven
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I use outflow as the BC of outlet. in fact, i had wanted to try the pressure outlet, but i don't know the factors that i have to fill
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July 2, 2013, 08:20 |
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#19 |
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rayan
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The condition of pressure outlet is valid when we have "one outlet" for two and more of outlet this condition is not valid, you must use the "equal flow rate" at outlets.. try to reduce the underelaxation at the minimum (0.1 or 0.2)
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July 2, 2013, 08:23 |
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#20 |
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steven
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so what should I put as the gauge pressure?
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