Predicting High-Lift LP Turbine Cascades Flows Using Transition-Sensitive Turbulence Closures

This paper discusses the application of different transition-sensitive turbulence closures to the prediction of low-Reynolds number flows in high-lift cascades operating in low-pressure turbine (LPT) conditions. Different formulations of the well known γ – R̃e_θt model are considered, and compared to a recently developed transition model based on the laminar kinetic energy (LKE) concept. All those approaches have been coupled to the Wilcox k – ω turbulence model. The performance of the transition-sensitive closures has been assessed by analyzing three different high lift cascades, recently tested experimentally in two European research projects (UTAT and TATMo). Such cascades (T106A, T106C, and T108) feature different loading distributions, different suction side diffusion factors, and they are characterized by suction side boundary layer separation when operated in steady inflow. Both steady and unsteady inflow conditions (induced by upstream passing wakes) have been studied. A particular attention has been devoted to the treatment of crucial boundary conditions like the freestream turbulence intensity and the turbulent length scale. A detailed comparison between measurements and computations, in terms of blade surface isentropic Mach number distributions and cascade lapse rates will be presented and discussed. Specific features of the computed wake-induced transition patterns will be discussed for selected Reynolds numbers. Some guidelines concerning the computations of high-lift cascades for LPT applications using RANS/URANS approaches and transition-sensitive closures will be finally reported.