Characterization of Low Reynolds Number Wind Turbine Aerodynamics by BEM Theory and PIV Measurements

Abstract

In this study, low Reynolds number wind turbine aerodynamics was considered. The overall goal was to characterize the flow in order to optimize the power output of the system. First, BEMT theory (Blade Element Momentum Theory) was formulated for this flow where Prandtl’s tip- and hub-loss corrections were included, as well as Glauert’s thrust coefficient correction. The theory was validated with experimental data from National Renewable Energy Laboratory (NREL) for larger scale wind turbines. Also, a physical model of a low Reynolds number horizontal-axis wind turbine (HAWT) was built. Particle Image Velocimetry (PIV) was used to calculate the velocity field around the HAWT. This allowed for planar measurements of the velocity field at different location in the wake of the rotor. The measurements were performed in a water channel allowing for better control of PIV seeding and improved flow visualization. PIV results allowed observation of the velocity field and vorticity field in the wake of the rotor. This data is currently being compared to BEMT theory suggesting good agreement.