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March 13, 2006, 15:11
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Dear all
In my case of chan
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Guest
Posts: n/a
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Dear all
In my case of channelOodles, the result of velocity seems laminar profile(parabolic profile) even at turbulent condition. I think something my setup is wrong, but I can't find it. Please help anybody! Values of my case model are below. Re number=30000. turbulenceProperties are LESmodel: Smagorinsky delta : vanDriest Values of Ubar and nu are written on transportProperties file. Y+ values are below 10. initial value of k is zero. inlet outlet conditions are cyclic. Other conditions are refered from tutorial sample. Best regards Tadashi |
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March 13, 2006, 16:42
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You should not start with init
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Senior Member
Hrvoje Jasak
Join Date: Mar 2009
Location: London, England
Posts: 1,905
Rep Power: 33  |
You should not start with initial k = 0. Estimate uPrime to several percent of uBar and do
k = 3/2 uPrime^2 as the initial guess of k. Hrv
__________________
Hrvoje Jasak Providing commercial FOAM/OpenFOAM and CFD Consulting: http://wikki.co.uk |
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March 14, 2006, 07:52
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Thank you very much Hrv.
I wi
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Guest
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Thank you very much Hrv.
I will try again with your advice. Tadashi |
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March 14, 2006, 08:32
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What is your initial value of
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Senior Member
Eugene de Villiers
Join Date: Mar 2009
Posts: 725
Rep Power: 21 |
What is your initial value of U?
The case will take ages to go turbulent from a uniform velocity unless you give it a push. |
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March 14, 2006, 09:12
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Hi Eugene
Initial value of
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#5 |
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Guest
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Hi Eugene
Initial value of U is as same as value of Ubar for uniform, and I could get turbulent condition with my case. But the result of mean velocity profile is quite different from that of RANS result. Is there any other value that I must check? Tadashi |
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March 14, 2006, 10:57
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Hmm, above you said your U pro
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#6 |
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Senior Member
Eugene de Villiers
Join Date: Mar 2009
Posts: 725
Rep Power: 21 |
Hmm, above you said your U profile was parabolic. The only way for that to happen is for the resolved flow to be laminar (at least in my experience).
Could you post a picture of the instantaneous U and k in the channel? |
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March 14, 2006, 11:52
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Please refer as below.
U
\
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#7 |
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Guest
Posts: n/a
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Please refer as below.
U \image(/home/tadashi/temp/LES_U.jpg) k \image(/home/tadashi/temp/LES_k.jpg) |
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March 14, 2006, 12:48
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Sorry, I am not good at these
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#8 |
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Guest
Posts: n/a
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Sorry, I am not good at these kinds.
U  k |
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March 24, 2006, 13:12
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Dear Eugene
Sorry, I couldn
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#9 |
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Guest
Posts: n/a
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Dear Eugene
Sorry, I couldn't upload pics. But I thought that the problem is cyclic boundary condition will just loose kinetic energy every iterations. Finaly, flow will become laminar. How to give kinetic energy to flow every iterations? Or is my understanding wrong? Thanks. |
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March 25, 2006, 09:00
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channelOodles already takes ca
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#10 |
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Senior Member
Eugene de Villiers
Join Date: Mar 2009
Posts: 725
Rep Power: 21 |
channelOodles already takes care of this via a mean pressure gradient that is adjusted to maintain the target mean velocity, Ubar, that is set in the transportProperties dictionary. Of course running normal oodels on a periodic flow will cause it to wind down.
Check the formatting section of the forum on how to upload pictures. |
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