Assessment of Vortex Induced Vibrations on Wind Turbines

Modern wind turbines are prone to Vortex Induced Vibrations (VIV). In the present work, an engineering semi-empirical framework is proposed that assesses VIV aero-elastic instabilities of wind turbine configurations. The procedure employs engineering tools relying on airfoil polars. It uses the state-of-the-art aero-elastic tool hGAST along with the EUROCODE VIV framework for steel structures extended to wind turbine configurations. The aero-elastic tool provides the missing modal input data (i.e. modal frequencies, total structural plus aerodynamic modal damping and modeshapes) to evaluate the semi-analytical expressions of the displacement and load amplitudes. Numerical results for single- and two-bladed configurations of the NREL 5MW Reference Wind Turbine (RWT) during assembly are presented, assessing turbine loads under the most unfavourable VIV scenarios examined.