Numerical and Experimental Investigation of the Reynolds Number and Reduced Frequency Effects on Low-Pressure Turbine Airfoils

This paper compares experimental and numerical data for a low-speed high-lift Low Pressure Turbine (LPT) cascade under unsteady flow conditions. Three Reynolds numbers representative of LPTs have been tested, namely, 5 × 10⁴, 10⁵, 2 × 10⁵; at two reduced frequencies, f_r = 0.5 and 1, also representative of LPTs. The experimental data was obtained at the low-speed linear cascade wind-tunnel at the Polytechnic University of Madrid using hot-wire, LDV and pressure tappings. The numerical solver employs a sixth order compact scheme based on the Flux Reconstruction method for spatial discretization and a fourth order Runge-Kutta method to march in time. The longest case ran 550 hours on 40 GPUs to reach a statistically periodic state. Pressure coefficients around the profile, boundary layer profiles and exit cross-section distributions of velocity, pressure loss defect, shear Reynolds stress and angle are compared against high-quality experimental data. Cascade loss and exit angle have also been compared against experimental data. Very good agreement between experimental and numerical data is seen. The results demonstrate the suitability of the present methodology to predict the aerodynamic properties unsteady flows around LPT linear cascades accurately.