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June 9, 2008, 12:09 |
SST k-omega convergence
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#1 |
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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)
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June 16, 2008, 06:59 |
Re: SST k-omega convergence
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#2 |
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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. |
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June 20, 2008, 08:45 |
Re: SST k-omega convergence
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#3 |
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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. |
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June 20, 2008, 13:37 |
Re: SST k-omega convergence
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#4 |
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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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