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-   -   Modeling instabilities using RANS? (http://www.cfd-online.com/Forums/fluent/70171-modeling-instabilities-using-rans.html)

thecfduser November 16, 2009 18:08

Modeling instabilities using RANS?
 
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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