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Investigating the Causes and Mitigating the Risks

EV Figure 1Edgewise vibration (EV) is an aeroelastic resonant phenomenon induced by the wind that can occur when a wind turbine is parked with a brake applied or idling (e.g. not producing power). While EV is an infrequent event, the authors have conducted several blade failure investigations that identified EV as the mechanism of failure. The investigations involved blades designed and manufactured by multiple entities, with blade lengths ranging from approximately 40 metres to more than 80 metres. This range encompasses most utility-scale blade lengths currently in production. EV is a specific case of vortex-induced vibration, where shed vortices in fluid flow around a structure impart forces to the structure, resulting in oscillatory motion. EV is characterised by increasing blade deflections (Figure 1), primarily in the edgewise direction, that (for the context of this article) results in blade damage.

By M. Malkin, Principal Engineer, and D. Griffin, Senior Principal Engineer, DNV GL, USA

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