Aeroelastic fragility analysis of wind turbine blades in turbulent flow

This work aims to assess the structural response and failure probabilities of wind turbine blades subjected to dynamic wind loading conditions, emphasizing the influence of an accurate wind model incorporating spatial coherence. An equivalent beam approach is exploited to simplify the complex blade structure. The aerodynamic forces are modeled using blade element theory. A realistic wind model, which accounts for spatial coherence and temporal variations across the turbine rotor plane, is used providing an accurate representation of turbulent wind fields compared to conventional simplified models. The results highlight the significant impact of wind conditions on the aeroelastic stability and failure likelihood of blades, particularly regarding the predictions of blade-to-tower strikes, showing that wind variability during operation greatly influences the blade tip dynamic response, possibly leading to impact with the tower in scenarios where static aeroelastic analysis does not predict the contact. The fragility analysis carried out highlights a maximum deflection of the blade reaching the 81.3% of the available clearance with the tower, within the operative wind speed range of the selected NREL 5 MW wind turbine benchmark, with no pitch control system activated, demonstrating the importance of implementing mitigation strategies to ensure safety in turbulent wind conditions.