SST k-omega convergence

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 June 9, 2008, 12:09 SST k-omega convergence #1 mauri Guest   Posts: n/a Sponsored Links Hi! I'm simulating a diffuser augmented wind turbine using a SST k-omega model. Residuals of continuity, turbulent kinetic energy and velocity decrease rapidly, but residuals of omega are stable (I mean really fixed on a constant value) on a higher value. Why? What can I do? I've got no problems with k-eps models (and the same mesh)

 June 16, 2008, 06:59 Re: SST k-omega convergence #2 Wiebe Guest   Posts: n/a Hello Mauri, There are a few things that you can try to do. What works really depends on your situation (mesh, steady sate or transient simulation, boundary conditions, etc.) - try to do some iterations while solving the turbulence equation only. - lower the relaxation factor for omega, or, if it is really low, try increasing it. - adapt the mesh to the gradient of omega. Good luck! Wiebe.

 June 20, 2008, 08:45 Re: SST k-omega convergence #3 Wiebe Guest   Posts: n/a Hello Mauri, Ironically I had the same problem the past few days. I didn't want to look up turbulence levels for the input boundary condition, so I set it to zero until i would. It turns out that the SST k-omega model doesn't like 0 for both k and omega as inlet boundary condition. Hopes this helps for you too. Wiebe.

 June 20, 2008, 13:37 Re: SST k-omega convergence #4 mauri Guest   Posts: n/a Hello Wiebe, I tried to run some simulations and thanks to your advice things are better, in terms of convergence rate. And of course another problem has arised: when I refine mesh in order to use enhanced wall functions with y+<5 (using adapt menu in fluent, both in conformal mode and in hanging node), then I get a non-physical solution, even starting iterations from a previous solution (which seems correct)! Sorry for still bothering you...and thanks a lot!!!

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