CFD Online Discussion Forums

CFD Online Discussion Forums (http://www.cfd-online.com/Forums/)
-   OpenFOAM Programming & Development (http://www.cfd-online.com/Forums/openfoam-programming-development/)
-   -   understanding the lien cubic low re model (http://www.cfd-online.com/Forums/openfoam-programming-development/92182-understanding-lien-cubic-low-re-model.html)

romant September 5, 2011 09:52

understanding the lien cubic low re model
 
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.

salehi144 March 3, 2012 04:19

LienCubicLowRe bugs
 
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?)

romant March 3, 2012 11:06

Quote:

Originally Posted by salehi144 (Post 347408)
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.

salehi144 March 3, 2012 11:47

paper
 
thanks Romant. thanks alot!

unfortunately i dont have access even to this paper :( :( :(

can you send me one of them?

Email: Salehi144@gmail.com


All times are GMT -4. The time now is 15:35.