FINITE ELEMENT ANALYSIS OF HORIZONTAL AXIS WIND TURBINES PERFORMANCE

This paper presents an aeroelastic formulation based on the Finite Element Method (FEM) to predict the performance of an isolated horizontal axis wind turbine. Hamilton's principle is applied to derive the equations of blade(s) aeroelasticity, based on a nonlinear beam model coupled with Beddoes-Leishman unsteady sectional aerodynamics. A devoted fifteen-degrees of freedom finite element, able to accurately model the kinematics and elastic behavior of rotating blades, is introduced and the spatial discretization of the aeroelastic equations is carried-out yielding a set of coupled nonlinear ordinary differential equations that are then solved by a time-marching algorithm. The proposed formulation may be enhanced to face the analysis of advanced blade shapes, including the presence of the tower, and represents the first step of an ongoing activity on wind energy based on a FEM approach. Due to similarities between wind turbine and helicopter rotor blades aeroelasticity, validation results firstly concern with the aeroelastic response of a helicopter rotor in hovering. Next, the performance of a wind turbine in terms of blade elastic response and delivered power are predicted and compared with available literature data.