# Trouble of LES case

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 March 13, 2006, 16:11 Dear all In my case of chan #1 tadashi Guest   Posts: n/a 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

 March 13, 2006, 17:42 You should not start with init #2 Senior Member   Hrvoje Jasak Join Date: Mar 2009 Location: London, England Posts: 1,783 Rep Power: 22 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

 March 14, 2006, 08:52 Thank you very much Hrv. I wi #3 tadashi Guest   Posts: n/a Thank you very much Hrv. I will try again with your advice. Tadashi

 March 14, 2006, 09:32 What is your initial value of #4 Senior Member   Eugene de Villiers Join Date: Mar 2009 Posts: 725 Rep Power: 13 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.

 March 14, 2006, 10:12 Hi Eugene Initial value of #5 tadashi Guest   Posts: n/a 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

 March 14, 2006, 11:57 Hmm, above you said your U pro #6 Senior Member   Eugene de Villiers Join Date: Mar 2009 Posts: 725 Rep Power: 13 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?

 March 14, 2006, 13:48 Sorry, I am not good at these #8 tadashi Guest   Posts: n/a Sorry, I am not good at these kinds. U k

 March 24, 2006, 14:12 Dear Eugene Sorry, I couldn #9 tadashi Guest   Posts: n/a 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.

 March 25, 2006, 10:00 channelOodles already takes ca #10 Senior Member   Eugene de Villiers Join Date: Mar 2009 Posts: 725 Rep Power: 13 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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