Aeroelastic Response and Stability of Wind Turbine Generators : Behavior of the Turbine Blade

Abstract

A mathematical model of an isolated blade of a horizontal axis wind turbine generator is presented to describe coupled motions of flap, Iag and torsion of the blade. An energy approach is employed to derive Lagrange's equation of motion. The blade is considered as a pretwisted beam of variable cross section to calculate the kinetic, dissipation and strain energies. Quasi-steady blade-element strip theory is applied to compute aerodynamic forces which account for the boundary layer shear winds and wind speed reduction due to tower shadow. The resulting equations, which have time -dependent coefficients, are solved numerically to obtain the steady-state response and stability of the blade. Wind tunnel tests were conducted using a l/25 scale model to ascertain theoretical predictions.