Dynamic and Aeroelastic Analyses of a Wind Turbine Blade Modeled as a Thin-Walled Composite Beam

In this paper, dynamic and aeroelastic analysis of a wind turbine blade modeled as an anisotropic composite thin-walled box beam is carried out. The analytical formulation of the beam is derived for the flapwise bending, chordwise bending and transverse shear deformations. The derivation of both strain and kinetic energy expressions are made and the equations of motion are obtained by applying the Hamilton’s principle. The equations of motion are solved by applying the extended Galerkin method (EGM) for anti-symmetric lay-up configuration that is also referred as Circumferentially Uniform Stiffness (CUS). As a result various coupled vibration modes are exhibited. This type of beam features two sets of independent couplings: i) extension-torsion coupling, ii) flapwise/chordwise bending-flapwise/chorwise transverse shear coupling. For both cases, the natural frequencies are validated by making comparisons with the results in literature and effects of coupling, transverse shear, ply-angle orientation, and rotational speed on the natural frequencies are examined and the mode shapes of the rotating thin-walled composite beams are further obtained. Blade element momentum theory (BEMT) is utilized to model the wind turbine blade aerodynamics. After combining the structural and the aerodynamic models, the aeroelastic analysis are performed and flutter boundaries are obtained.