Gravo-aeroelastically-scaled demonstrator field tests to represent blade response of a flexible extreme-scale downwind turbine

Operational experimental testing results for a 44.5 m diameter wind turbine rotor were obtained to investigate moments and deflections of a downwind, coned wind turbine with lightweight flexible blades. These results were non-dimensionally compared against OpenFAST predictions of the manufactured sub-scale rotor as well as the full-scale concept rotor. The full-scale, 13-MW Segmented Ultralight Morphing Rotor is a 2-bladed downwind rotor with load aligned blades. The 1/5th sub-scale demonstrator rotor (SUMR-D) was designed to match the nondimensional gravo-aeroelastic flapwise loads, deflections, and dynamics of its full-scale counterpart. The sub-scale model was tested at the National Renewable Energy Laboratory's Flatirons Campus (NREL FC) with gusts that are 2.6 times higher than that of a scaled environment. To withstand the site conditions, the manufactured SUMR-D rotor employed higher inboard mass density and stiffness relative to that of an ideally-scaled model. The experimental results are compared against computational non-dimensional characteristics: tip-speed ratios, RPM, tip deflections, and flapwise bending moments. Despite the robust blades for NREL FC testing, the sub-scale experimental model was found to reasonably represent the dynamics predicted by OpenFAST. These results demonstrate the potential of low-cost high-fidelity sub-scale testing for novel extreme-scale turbine designs.