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-   -   k-w Turbulence model implementation (http://www.cfd-online.com/Forums/main/10324-k-w-turbulence-model-implementation.html)

 suneesh November 20, 2005 11:29

k-w Turbulence model implementation

Dear Friends,

I am working on the implementation of k-w turbulence model for 2d flows and I have a few problems, which I would like to clear. The turbulence model of Wilcox(1988) has been implemented by me in a coupled fasion, with implicit time stepping.

1. The code blows off after reaching a residue of 1e-4 on fine meshes.

2. k and w are becoming negative.

There are a few references that talk about limiting k and w, but the procedure is not well explained. I believe that the blow up of the code and the simultaneous degradation in the contours is because of improper limiting. It would be a big help if anyone could clarfiy these doubts and/or point to references that contain substantial discussions in this regard.

 pkm November 21, 2005 03:15

Re: k-w Turbulence model implementation

normally the k starts attaining -ve value first.then obviously solution blows up. adopt linearisation of k -eqn. also ensure attainable convergence of the continuity eqn.

 peter.zhao November 23, 2005 11:12

Re: k-w Turbulence model implementation

There are a lot of lower limits on K and omega to prevent them below unphysical value. For example, From http://cfl3d.larc.nasa.gov/Cfl3dv6/cfl3dv6.html, CFL3d imposes the below limit on omega and K: If either nondimensional omega or non-dimensional K drops equal to or below 1.0e-20, they will be reset to 1.0e-20. From http://www.grc.nasa.gov/WWW/winddocs...urbulence.html, WIND-US software sets kmin and &epsilon;min to 10âˆ'10 and 10âˆ'12, respectively. You can also find a more complicate formula to limit omega and K from www.taurus.dlr.de/user_guide/user_guide.pdf. Which way is the best rests on the problem you solve

 suneesh November 23, 2005 12:19

Re: k-w Turbulence model implementation

Dear Peter Zhao and pkm,

Thanks for the suggestions. I shall check them out. I would also like to know if some upper limits are provided for k and w, and also like to know if there are limits on the eddy viscosity.

Regards, Suneesh

 FELIPE November 23, 2005 18:35

experimetal or numerical data channel flow

Dear Friends

I am working on the simulation of turbulent mixed convection in vertical channel flow , I have validated my code for forced convection and the natural convection in a tall and square cavity, I want to validate my code for mixed o natural convection in the vertical channel flow, Please anyone can send to me experimental or numerical data for the validation code.

sincerely thank a lot

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