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-   -   Transition k-kl-omega parameters at inlet (http://www.cfd-online.com/Forums/fluent/101678-transition-k-kl-omega-parameters-inlet.html)

ticsh May 10, 2012 09:47

Transition k-kl-omega parameters at inlet
 
Hi!
I'm testing Transition k-kl-omega turbulence model. I was told that this model is very sensitive to initial parameters at flow inlet. So at boundary conditions (in my case pressure inlet) I have to input the value of laminar kinetic energy (kl), but i can`t find any equation in user manual which will help me to estimate this value.
Has anybody got information obout estimating of kl for this turbulence model?

sk0pa May 11, 2012 02:03

Hello! I'm interested in this problem too.

ticsh May 11, 2012 03:14

I have found some information. In Fluent additional materials it is written that this parameter should be always equal 10^-6. Is it correct?

Far May 11, 2012 03:39

The only parameter which is important for transition model is the turbulence intensity. 2nd less important parameter is the length scale (in some papers they give value of 0.3 chord as length scale.) but it has little effect as per recent studies(I can send you papers)


Edit : instead of 0.3 chord the correct formula is 0.03 chord or 3% of chord

ticsh May 11, 2012 04:58

Quote:

The only parameter which is important for transition model is the turbulence intensity. 2nd less important parameter is the length scale (in some papers they give value of 0.3 chord as length scale.) but it has effect as per recent studies(I can send you papers)
Ok, thanks for information. Than I have another question about this model: is estimation of turbulence intensity and length scale the same as for another turbulence models?

Far May 11, 2012 05:06

same but for some purpose.

In other models turbulence intensity has no impact (as you are solving the problem fully turbulent). Whereas in transition models increasing/decreasing the turbulence intensity change the behaviour of transition from laminar to turbulent state.

ticsh May 11, 2012 05:24

Quote:

Originally Posted by Far (Post 360526)
same but for some purpose.

In other models turbulence intensity has no impact (as you are solving the problem fully turbulent). Whereas in transition models increasing/decreasing the turbulence intensity change the behaviour of transition from laminar to turbulent state.

Ok, thank you very much. I will try different initial turbulence intensity to see the change of transition zone behaviour.

Far May 11, 2012 05:38

pm your email id and I shall send you the latest papers so that you get the flavour of it.

micro11sl May 11, 2012 10:27

Where did you find the information?
 
Quote:

Originally Posted by ticsh (Post 360488)
I have found some information. In Fluent additional materials it is written that this parameter should be always equal 10^-6. Is it correct?

Hi,
Where did you the information? I can't find much information in the help documents.

Sheng

ticsh May 11, 2012 11:37

Quote:

Originally Posted by micro11sl (Post 360612)
Hi,
Where did you the information? I can't find much information in the help documents.

Sheng

At Ansys Costumer Portal

Goutam February 21, 2014 10:45

Quote:

Originally Posted by Far (Post 360536)
pm your email id and I shall send you the latest papers so that you get the flavour of it.

Could you please email me the papers:

ranamath06@gmail.com

Far February 21, 2014 11:09

here you go :)
 
Shared for every one.

https://dl.dropboxusercontent.com/u/...tionpapers.zip

Goutam February 21, 2014 12:29

Quote:

Originally Posted by Far (Post 476043)

Sorry, this link is not working.

Far February 22, 2014 13:04

please check it again...

malv83 June 17, 2016 14:37

New 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


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