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Modeling instabilities using RANS?

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Old   November 16, 2009, 18:08
Default Modeling instabilities using RANS?
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Hello all,
i would appreciate greatly if anyone can respond to my question.
Lets say i am modelling von Karman vortex using RANS models. The geometry is symetric, so how a Rans model would be able to predict instability???
Instability=loss of symetry, and i cant see how a RANS model can predict this. They will always give a symetrical solution.

I had the same problem when modeling a turbulent flow in a pipe. I use unsteady solver, but when monitoring velocities, i see that when i have convergence, the velocity is constant at a given point (in respect to time)
Must we include perturbation to a RANS model so we can be able to break the symetry???

Best regards
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