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-   -   k-kl-w turbulence model (https://www.cfd-online.com/Forums/fluent/68120-k-kl-w-turbulence-model.html)

 PrandtlGlawert September 7, 2009 19:23

k-kl-w turbulence model

Hi everybody,

I´ve just asked some people what could they tell me about the k-kl-w turbulence model and the answer i´ve got is that it´s a kind of turbulence recently released for commercial versions, and that it has been developed specifically for laminar-turbulent transition.

Could somebody tell me something more about that? It would be VERY useful for me, i can find no information on the web about it.

My other problem is that it´s too difficult for me to get a good convergence on that model, but i do have more time to face this problem.

Any website or information about the k-kl-w model?

 denizen September 8, 2009 01:12

you can find comprehensive information in fluent users's guide and theory guide.

regards

 delfel September 9, 2009 14:14

Hello,

I've never used that model, but I imagine that modeling transition to turbulence requires a pretty fine mesh. The fluent user's guide should have the info. about grid requirements.

-sean

 PrandtlGlawert September 9, 2009 15:22

Thx for your replies m8s :):):) :rolleyes::rolleyes::rolleyes:

 Chenel November 5, 2009 11:05

sorry for my English, i looking for information about equations of k-kl-w model. i don´t know if k-kl-omega model is the same that k-kl model. i see fluent user guide but 3 equations model not appears.
thanks you

 Far September 19, 2011 17:12

actually this model is going through the development. first model used the epsilon as turbulent length scale variable. in 2nd phase; model used the omega equation but still epsilon in other two equations. last model, which fluent has I believe, uses the omega equation with omega variable in all other equation.

besides that, there are large changes in other auxiliary equations and limiters (as you there are 24 constants in this model), which are more important to the overall model capability. among them two are very much important : one controls the by pass transition and other controls the natural transition

I can send you all three papers for these three versions.

 Marabelle September 20, 2013 05:50

Quote:
 Originally Posted by Far (Post 324749) I can send you all three papers for these three versions.
@ Far!
Could you also send them to me? I only found few information to the k-kl-w model and I really want to understand it...

 Far September 20, 2013 10:23

email plz......

 Marabelle September 24, 2013 05:54

@Far. I sent you a personal message with my emailadress. Thank you very much!

 s.m December 1, 2013 15:40

Dear Far, whould you please send me the papers related to k-kl-omega?
i really need som information about it.
here you are, this my email :

Thank you very much:o

 Monstrobolaxa March 7, 2014 13:31

SO it's been a while since this topic was last discussed.

I've used the k-kl-w and compared computational with experimental surface flow vis. The results match perfectly with transition being predicted within 2% of the wing chord. But I've only be able to compare these results on a few limited cases. Drag and lift are also within 3% of experimental.

Due to issues this turbulence model I've gone back to k-w SST, but am suffering from problems as the forces are now 5%drag and 15%lift off!

With the k-kl-w I've had flow reversal being created at the outlet, which grows and grows. Checking the the turbulence intensity I've found that there is a spot near the outlet where the side wall and moving ground where turbulence is created....leading divergence sometimes or over 1000 faces having reverse flow on the outlet.

My outlet is about 7 body lengths behind the body and upstream of the problematic area turbulence intensity is close to zero.

Anyone suffering from the same? Any miracle solutions?

 Far March 7, 2014 14:24

what problems you are getting with k-kl-kw model?

 ahmed ramadan May 14, 2015 06:55

Could you send me papers about the model i m going to work on changing some constants of it so i have to know all thing about it

 CFDYourself May 22, 2015 05:04

Quote:
 Originally Posted by delfel (Post 229042) Hello, I've never used that model, but I imagine that modeling transition to turbulence requires a pretty fine mesh. The fluent user's guide should have the info. about grid requirements. -sean
Hi, I'm new here, this is my first post.

I can confirm what delfel has said. both k-kl-w and transition SST models in fluent require a fine mesh. Fluent reccomend y+ = 1 for the first cell height, and a growth rate of 1.1 in the turbulence modelling lit

 malv83 June 17, 2016 14:35

New version of the model

After 8 years, there is a new version (or new model) of the k-kl-omega model.

There are a few problems with the k-kl-omega model in the farfield. One of them is the growth of Laminar Kinetic energy when separation occurs. Lopez and Walters have a paper (have not been published yet) correcting this issue:

Maurin Lopez. D. K. Walters. “A recommended correction to the k-kl-omega transition sensitive eddy-viscosity model”. Journal of Fluid Engineering.

This correction has to be made to the 2008 k-kl-omega model from now on.

Now, Lopez and Walters also developed a new transitional model (k-omega-v2) as an alternative to the k-kl-omega one. This new model has more capabilities (it is more reliable) than the k-kl-omega model, especially in the farfield computations. Fortunately the paper for this new model is already publish.

Maurin Lopez. D. K. Walters. “Prediction of transitional and fully turbulent free shear flows using an alternative to the laminar kinetic energy approach”. Journal of Turbulence, Vol 17, Iss. 3, 2016.

If you see the papers, you will immediately see how the k-kl-omega model is not good for free shear flows, and how the new model corrects all those issues. From now on, k-kl-omega users have to start using the new k-omega-v2 model.

Hope this helps

 Far June 17, 2016 14:41

which version?

 malv83 October 13, 2016 12:14

Maurin Lopez. D. K. Walters. “Prediction of transitional and fully turbulent free shear flows using an alternative to the laminar kinetic energy approach”. Journal of Turbulence, Vol 17, Iss. 3, 2016.

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