k-e in laminar flow
 

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.

Re: k-e in laminar flow
 

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.

Re: k-e in laminar flow
 

Ok. Thank you for your answer.

Re: k-e in laminar flow
 

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.

Re: k-e in laminar flow
 

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.