URANS Prediction of the Effects of Upstream Wakes on High-Lift LP Turbine Cascades Using Transition-Sensitive Turbulence Closures

A URANS solver has been applied to the analysis of unsteady effects induced by incoming wakes in high-lift, low-Reynolds-number cascade flows. The study has been carried out using a novel, transition-sensitive, turbulence model. It is based on the coupling of additional transport equations, one for the so-called laminar kinetic energy (LKE) and one for a turbulence indicator function, with both linear eddy-viscosity and algebraic Reynolds stress models. The transition modelling strategy and its coupling with the turbulence equations is conceived as an extension of the laminar kinetic energy concept for unsteady flow calculations. Details on the role of each model component will be presented and discussed. Three high-lift bladings (T106A, T106C, and T2), recently tested in the framework of two European research projects were considered for the present study. The cascades are characterized by separated flow transition in steady conditions. Traverse measurements within upstream rotating bar wakes were available for code validation purposes. They have been used to provide time-dependent inlet conditions for unsteady analyses. A detailed comparison between measurements and computations, in terms of blade loading distributions and cascade lapse rates will be presented and discussed. Some specific features of wake-induced transition will also be discussed. Results obtained with the proposed model show its ability to predict the major effects of passing wakes on the boundary layer development and loss characteristics of high-lift cascades operating in LP-turbine conditions.