Researchers Francisco J. G. de Oliveira, Martin Bourhis, Zahra Sharif Khodaei, and Oliver R. H. Buxton from the University of Cambridge have conducted a study to better understand the complex aerodynamic interactions between wind turbine blades and their wakes. Their work, published in the Journal of Fluid Mechanics, focuses on the relationship between blade structural response and the flow structures generated in the turbine’s wake, which is crucial for predicting fatigue damage and optimizing turbine performance.
The researchers implemented a novel technique that allows simultaneous measurement of spatially distributed blade strain and wake dynamics for a model wind turbine under controlled conditions. They used a 1-meter diameter three-bladed rotor equipped with distributed Rayleigh backscattering fiber-optic sensors to measure blade strain. Synchronized hot-wire anemometry captured wake evolution up to four rotor diameters downstream. The experiments covered a wide range of free-stream turbulence (FST) and tip-speed ratio (λ) conditions, totaling 21 cases.
The results revealed that aerodynamic-induced strain fluctuations peak at a tip-speed ratio of approximately 3.5, close to the design tip-speed ratio of 4. At design conditions, the blade’s tip experiences up to 75% of its total fluctuating strain from aerodynamically-driven strain fluctuations. Spectral analysis showed frequency-selective coupling between wake flow structures and the blade response, dominated by flow structures dynamically related to the rotor’s rotating frequency, such as tip vortex structures.
This research establishes a data-driven foundation for validating future aeroelastic models and developing fatigue-informed control strategies. For the energy industry, understanding these interactions can lead to improved wind turbine design and operation, enhancing efficiency and reducing maintenance costs. By optimizing turbine performance and predicting fatigue damage more accurately, wind farms can achieve better overall performance and longevity.
This article is based on research available at arXiv.