# understanding the lien cubic low re model

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 September 5, 2011, 09:52 understanding the lien cubic low re model #1 Senior Member     Roman Thiele Join Date: Aug 2009 Location: Stockholm, Sweden Posts: 366 Rep Power: 13 Hej, can somebody maybe explain to me why the implementation of the lor reynolds number turbulence model by lien, chen and leschziner has such a complicated implementation of the non linear stress, one that does not seem to adhere to the paper (Lien et al., Low-Reynolds-number eddy-viscosity modelling based on non-linear stress-strain-vorticity relations, Proc. 3rd Symp. on Engineering Turbulence Modelling and Measurements, 1996, Crete, Greece) It seems that there are some simplifications steps taken, but I can't seem to understand those, because sometimes only one of the terms is missing like in the fifth term Code: ``` ( C5viscosity_, dimensionedScalar("0", C5viscosity_.dimensions(), 0.0) )*gradU_``` compared with the paper, where one should go with Code: ``` ( C5viscosity_, dimensionedScalar("0", C5viscosity_.dimensions(), 0.0) )*(gradU_+gradU_.T() )``` It is not visible how those simplifications were taken. If someone understands this model, maybe he/she can help me understand it as well. __________________ ~roman

 March 3, 2012, 04:19 LienCubicLowRe bugs #2 New Member   Saeed Salehi Join Date: Aug 2010 Posts: 17 Rep Power: 8 Hi Romant. I've been working on LienCubicKELowRe lately. I think there is some bugs in it. Probably one of them is that you mentioned. another one is it the nonlinearstresses are not multiplied by fMu which is wrong. The epsilon equation is also seemed to be different from usual. Also i dont know about those coefficient if they are correct or not. because i dont have that paper you mentioned. i did A LOT of searches about it. but i couldn't find it. (do you have it?)

March 3, 2012, 11:06
#3
Senior Member

Roman Thiele
Join Date: Aug 2009
Location: Stockholm, Sweden
Posts: 366
Rep Power: 13
Quote:
 Originally Posted by salehi144 Hi Romant. I've been working on LienCubicKELowRe lately. I think there is some bugs in it. Probably one of them is that you mentioned. another one is it the nonlinearstresses are not multiplied by fMu which is wrong. The epsilon equation is also seemed to be different from usual. Also i dont know about those coefficient if they are correct or not. because i dont have that paper you mentioned. i did A LOT of searches about it. but i couldn't find it. (do you have it?)
Hej,

so yeah, I have the paper, but I have it only in paper form. I will be able to have access again next week. There is also a second paper that is needed to full understand the paper by Lien, which is

Craft, T.J., B.E. Launder, and K. Suga. “Development and Application of a Cubic Eddy-viscosity Model of Turbulence.” International Journal of Heat and Fluid Flow 17 (April 1996): 108–115

together with

S. B. Pope, A more general effective-viscosity hypothesis, Journal of Fluid Mechanics, 72 (1975), p. 331.
__________________
~roman

 March 3, 2012, 11:47 paper #4 New Member   Saeed Salehi Join Date: Aug 2010 Posts: 17 Rep Power: 8 thanks Romant. thanks alot! unfortunately i dont have access even to this paper can you send me one of them? Email: Salehi144@gmail.com Last edited by salehi144; March 5, 2012 at 02:04.

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