Hi.

I was wondering. Can a turbulent model like (eg.) k-e or RSM calculate a laminar flow correctly?

If no, what do one do in a case where there are both laminar and turbulent flow zones?

Thanks.

You can't use k-epsilon to do laminar flow. If you have regions of both laminar and turbulent flow then you need a method for predicting the transition point as well as a method of damping the turbulent contributions (so that they are zero in laminar flow). I don't know of any schemes that can do this in general flow configurations. Predicting flow transition is still very much an open problem and is an active area of research.

Ok. Thank you for your answer.

Some codes can deal with transition alledgedly, but in fact you supply the transition region a priori as far as I understand and the topic of a self-determining transition is indeed an active field of research.

The Wilcox book (Turbulence modeling for CFD) gives a good overview of transition modelling with the k-epsilon and k-omega models.

alternatively, try:

D.C. Wilcox "Simulation of Transition with a Two-Equation Turbulence Model" AIAA Journal, Vol 32, No. 2, February 1994.

this is mainly about the k-omega model but does give a good insight into the problems with two-equation models and transition.