[ticsh]

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]

Hello! I'm interested in this problem too.

[ticsh]

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]

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]

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]

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]

Originally Posted by Far

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]

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

[micro11sl]

Originally Posted by ticsh

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]

Originally Posted by micro11sl

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

Sheng

At Ansys Costumer Portal

[Goutam]

Originally Posted by Far

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]

Shared for every one.

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

[Goutam]

Originally Posted by Far

Shared for every one.

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

Sorry, this link is not working.

[Far]

please check it again...

[malv83]

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