# kkl-omega coefficients

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 April 5, 2012, 12:36 kkl-omega coefficients #1 Member   Join Date: Jun 2011 Posts: 38 Rep Power: 8 Sponsored Links Hey All! I'm doing 3D wing analysis using the kkl-omega turbulence model. Does someone of you know how to calculate kl kt omega nut and nuTilda ? thanks in advance Christian

 June 6, 2012, 04:23 #2 Member   wided Join Date: Jul 2010 Posts: 54 Rep Power: 9 Hi ChrisPro, you calculate omega and k like you do for the komegaSST or komega model. The other kl, kt you can get the values by looking at the paper: "A three equation Eddy-viscosity model for Reynolds-Averaged-Navier-Stokes simulations of transitional flow". Journal of Fluids Engineering 2008. Good luck.

 June 6, 2012, 05:29 #3 Member   Join Date: Jun 2011 Posts: 38 Rep Power: 8 Hey! Thanks for your reply! I already did it but for the others who have a look at this thread: you can leave away k kt is calculated like k in the other turbulence models: T*u_inf = sqrt(2/3*kt) / U_inf in freestream one can set kl to 0 nut = Cmü,std * kt/omega omega is the same as in the kOmegaSST model Cmü,std = 0.09 I discovered that you can leave out nuTilda as well. The results are the same, but the timesteps it takes to get the desired residual is a bit higher! greets Christian

 June 6, 2012, 05:31 #4 Member   wided Join Date: Jul 2010 Posts: 54 Rep Power: 9 You are welcome ChrisPro. I am also working with kklomega, but my problem is the y+ = 1 condition which is not easy to satisfy while keeping the grid size manageable.

 June 6, 2012, 14:53 #5 Member   Join Date: Jun 2011 Posts: 38 Rep Power: 8 that's true! at the moment I simulate a case which runs since yesterday morning on a 24core machine... (and now its 8.53pm in my time zone ) What experienced have you made with the calculated Cl and Cd values? With y+ = 6 I also got good residuals ( < e-06 ) but the values for Cl and Cd where much lower than expected. greets

 June 7, 2012, 04:03 #6 Member   wided Join Date: Jul 2010 Posts: 54 Rep Power: 9 Hi ChrisPro, for the moment I have no results yet, just began the struggle with the mesh to make it y+ conform without ending up with trillions of elements . I will share my findings when I have some data. I am also considering DES as it is less demanding meshwise.

 February 13, 2014, 05:26 #7 Member   Ye Zhang Join Date: Dec 2009 Location: Delft,Netherland Posts: 92 Rep Power: 9 Hi ChrisPro I am also interested in kklomega transition model. I have validated it for 2D airfoil, but not successful with 3D complex wing, it also have convergence problem. Would you please show your fvScheme and BC setting? and what about your solver? steady solver or transient solver? Thank you! Best regards, Ye

 June 16, 2014, 11:37 #8 Senior Member   M. Montero Join Date: Mar 2009 Location: Madrid Posts: 124 Rep Power: 10 I really hope someone could help me. I am trying to simulate a simple 2D airfoil with kkl omega model. My bcs are for wall are: nut=zeroGradient omega=zero Gradient kt=0 kl=0 My setting are: U=50m/s TI=1% turbulent length scale=0.01m So: kt=0.375 omega=61.23 nut=0.00055 I have use a very low relaxation factors, but I do not obtain good results. My mesh, runned with SA (nutSpaldingWallFunction) runs correctly: maximum yplus=2 ( just at TE region). Minimum=0.1. Average = 0.3 https://drive.google.com/folderview?...VE&usp=sharing

 August 18, 2015, 15:30 #9 New Member   Ranjan Join Date: Apr 2014 Posts: 16 Rep Power: 5 Hi Kidmax I am trying to get some airfoil results using kkl-omega model with PimpleFoam. May I ask how your results looked like ? I am currently getting very high cl & cd values. Thanks in advance

 June 17, 2016, 15:09 new model #10 New Member   Alberto Join Date: Sep 2013 Posts: 24 Rep Power: 5 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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