Aerodynamic damping of an offshore wind turbine in operational and parked conditions: A comparison between simulations and measurements

Aerodynamic damping can have a large impact on the lifetime of an offshore wind turbine. In order to extend the lifetime of offshore wind turbines it is of high interest to better understand the dynamics of an offshore wind turbine subjected to wind action. This will allow us to identify and avoid resonant behaviour, to quantify the dynamic response, to give indications about the current state of the offshore wind turbine and eventually to increase the lifetime of these structures. In his study, an offshore wind turbine has been considered in both operational and parked conditions to calculate the aerodynamic damping at different wind speeds. Operational Modal Analysis (OMA) is used to identify the natural frequencies and damping values of the modes of an offshore wind turbine present in the response due to the stochastic excitation of ambient loads. Simulations are performed in HAWC2 an aeroelastic code which is developed at Risø DTU. The simulation results are compared with the measurements obtained from a long-term monitoring campaign of a Vestas V90 3MW wind turbine in the Belgian North Sea.