An Overview of Possible Aeroelastic Instabilities for Wind Turbine Blades

Abstract

Aeroelastic instabilities can be disastrous for wind turbines. In the early years of wind turbines, aeroelasticity was not a problem, but once wind turbines became larger than 500 kW, some turbines experienced problems due to aeroelastic instabilities. Therefore it is important to design wind turbines with full knowledge of possible aeroelastic instabilities. Different known possible wind turbine blade instabilities are examined and investigated. Stall flutter and flap-lag-stall flutter have been investigated in more detail, showing the possibility of these instabilities occurring on wind turbines, because these instabilities have had less exposure in wind energy literature. Negative damping of the edgewise mode, negative damping of the flap mode and classical flutter are also discussed. The examples show that the knowledge already gained in the field of helicopter aeroelasticity can be very useful. However, the differences between helicopters and wind turbines are such that the results for helicopters cannot simply be copied to wind turbines. There are several instabilities that occur on wind turbines and are less relevant for helicopters.