Sviluppo di un modello computazionale per l'analisi aeroelastica di aerogeneratori

This report presents the activity performed in the framework of the national project RITMARE in fulfillment of the SP1-WP2-AZ6-UO02 work package tasks. In details, this report presents an aeroelastic formulation based on the Finite Element Method (FEM) for performance and stability predictions of isolated horizontal axis wind turbines. Hamilton's principle is applied to derive the equations of blade aeroelasticity, by coupling a nonlinear beam model with Beddoes- Leishman sectional unsteady aerodynamics. A devoted fifteen-degrees-of-freedom finite element to model kinematics and elastic behaviour of rotating blades is introduced. Spatial discretization of the aeroelastic equations is carried-out to derive a set of coupled nonlinear ordinary differential equations solved by a time-marching algorithm. The proposed formulation may be enhanced to face the analysis of advanced-shape blades, as well as the inclusion of the presence of the tower. Due to similarities between wind turbine and helicopter rotor blades aeroelasticity, validation results firstly concern with the aeroelastic response of helicopter rotors in hovering. Then, the performance of a wind turbine in terms of blade elastic response and delivered thrust and power is predicted and compared to that provided by a validated aeroelastic solver based on a modal approach as well as with experimental data. The present report collects revised results and discussions from the following published journal paper: Calabretta, A. et al. (2015), "Assessment of a FEM-based Formulation for Horizontal Axis Wind Turbine Rotors Aeroelasticity," Applied Mechanics and Materials, Vol. 798 (2015), pp. 75-84.