An aeroelastic model for the design of bend-twist coupled wind turbine rotor blades

Abstract

The present master thesis is devoted to the implementation of a bend-twist elastic coupling evaluation procedure which is robust and precise with relatively low computational time. The evaluation process used a 2D cross sectional analysis to divide the rotor blade into several cross sections and derive their properties. Subsequently, the 1D anisotropic finite element method was implemented to create the beam model from the cross sections and calculate the element stiffness. To analyze this beammodel, the aerodynamic loads on the blade were calculated based on the blade element momentum method. Three coupled blade designs were analyzed and compared with an uncoupled reference blade. Several nonlinear loading conditions were studied and as results, the blade characteristics, load mitigation, power and energy generation were calculated. In conclusion, the results show low computational cost compared to the conventional 3D finite element models. However, the computational time highly depends on the number of cross sections. Moreover, with acceptable number of cross sections, high precision can be achieved and the nonlinear behavior of properties of the coupled blades can be captured. These findings prove the efficiency and precision of the new evaluation process. Moreover, it can be used as a preliminary analysis tool for the coupled blade designs.