# k-w Turbulence model implementation

 Register Blogs Members List Search Today's Posts Mark Forums Read

 November 20, 2005, 11:29 k-w Turbulence model implementation #1 suneesh Guest   Posts: n/a Sponsored Links 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. Thanks in advance, Suneesh

 November 21, 2005, 03:15 Re: k-w Turbulence model implementation #2 pkm Guest   Posts: n/a 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.

 November 23, 2005, 11:12 Re: k-w Turbulence model implementation #3 peter.zhao Guest   Posts: n/a 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 εmin 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

 November 23, 2005, 12:19 Re: k-w Turbulence model implementation #4 suneesh Guest   Posts: n/a 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. Thanks in advance, Regards, Suneesh

 November 23, 2005, 18:35 experimetal or numerical data channel flow #5 FELIPE Guest   Posts: n/a 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

 Thread Tools Display Modes Linear Mode

 Posting Rules You may not post new threads You may not post replies You may not post attachments You may not edit your posts BB code is On Smilies are On [IMG] code is On HTML code is OffTrackbacks are On Pingbacks are On Refbacks are On Forum Rules

 Similar Threads Thread Thread Starter Forum Replies Last Post msrinath80 OpenFOAM Running, Solving & CFD 18 March 3, 2015 06:36 Michiel CFX 12 January 25, 2010 04:20 Andy Chen FLOW-3D 4 January 1, 2010 22:45 ganesh Main CFD Forum 0 March 6, 2006 13:23 Mohammad Kermani Main CFD Forum 2 December 26, 1999 03:56