Turbulence model in transition regime

PK

I generally solve airflow problems in moderately complex geometries, using FLUENT. The geometries always exhibit significant recirculation / vortex formation at high flow rates (Re=4000). But at lower flow rates in transition regime (say Re=2200), should I be treating the flow problem as a "laminar" one "turbulent"? Genrally I use k-e model in Fluent for turbulence at higher flowrates. Should I still use the k-e model, with a different set of model parameters to suit the transition regime? Can anyone send me some good references regarding the k-e values at various renges of Re? THanks and regards, Prashant