CALCULATION OF TRANSITIONAL BOUNDARY-LAYERS WITH AN IMPROVED LOW-REYNOLDS-NUMBER VERSION OF THE K-EPSILON TURBULENCE MODEL

Several well-known low-Reynolds-number versions of the kappa-epsilon models are analyzed critically for laminar to turbulent transitional flows as well as near-wall turbulent flows from a theoretical and numerical standpoint. After examining apparent problems associated with the modeling of low-Reynolds-number wall damping functions used in these models, an improved version of the kappa-epsilon model is proposed by defining the wall damping factors as a function of some quantity (turbulence Reynolds number Re-t), that is only a rather general indicator of the degree of turbulent activity at any location in the flow rather than a specific function of the location itself, and by considering the wall limiting behavior, the free-stream asymptotic behavior, and the balance between production and destruction of turbulence. This new model is applied to the prediction of ( I) transitional boundary layers influenced by the freestream turbulence, pressure gradient, and heat transfer; (2) external heat transfer distribution on the gas turbine rotor and stator blade under different inlet Reynolds number and free-stream turbulence conditions. It is demonstrated that the present model yields improved predictions.