URANS PREDICTIONS OF THE EFFECTS OF SYNTHETIC JETS ON THE SEPARATED, TRANSITIONAL FLOW OVER A LOW-PRESSURE-TURBINE-LIKE FLAT PLATE

A URANS solver has been applied to study the effects of a synthetic jet actuator on the laminar boundary layer separation over a flat plate with adverse pressure gradient. The pressure distribution over the fiat plate is representative of the suction side of a ultra-high-lift, LP-turbine airfoil. Measurements for several Reynolds numbers, are provided via experimental tests carried out in the framework of the European project TATMo (Turbulence and Transition Modelling for Special Turbomachinery Applications). The actuator device, in the form of a two-dimensional slot, has been conceived in order to obtain jet aerodynamic characteristics suitable for separation control. The study has been carried out using a novel, transition-sensitive, non-linear eddy-viscosity model. It is based on the coupling of an additional transport equation for the so-called laminar kinetic energy (LKE) to a realizable, quadratic eddy-viscosity model that provides an explicit algebraic formulation for the Reynolds stresses. The analysis covers steady as well as unsteady cases characterized by different actuator frequencies. Comparisons between measurements and computations are presented. The suitability of the proposed approach to simulate the time- and phase-averaged effects of a synthetic jet for boundary layer control at typical operating conditions of high-lift LP-turbine blades will be discussed in detail.