Aeroelastic flutter correlation analysis and structure optimization of wind turbine blades under multiple operating conditions based on aerodynamic damping

Aeroelastic stability is a complex and hot issue which still poses a great challenge to blade design for large wind turbines. The difficulty of aeroelastic design for wind turbine blades lies in the unknown underlying correlation between various design variables and diverse flutter modes under multiple operating conditions. In this paper, an aeroelastic analysis model for wind turbine blade is established to investigate the flutter characteristics of large wind turbine blades, based on the composite laminated plates theory, the aerodynamic calculation model, and the Euler-Bernoulli beam model. The main modal aerodynamic damping ratios under normal and parked conditions are calculated. The correlation between the layer design parameters and the flutter characteristics is quantitated and the significant parameters are recognized. The influence of the cap-web configuration of the blade on the flutter characteristics is quantified using the univariate analysis and the multi-factor-orthogonal test method. The trade-off relationship of the aerodynamic damping characteristics under two operating conditions is identified. The aeroelastic analysis model is embedded into the multi-objective aeroelastic optimization. Three aeroelastic optimization schemes are proposed, compared, and validated in the case study. Results show that, compared with the original scheme, the first-order flap-wise aerodynamic damping at the rated condition and the first order edgewise aerodynamic damping at the strong wind condition are increased by 17.839% and 12.387% respectively. The maximum displacement amplitudes at the rated condition and at the strong wind condition decrease by 32.13 % and 20.34 % respectively. The proposed collaborative optimization design method demonstrates strong effectiveness in enhancement of aeroelastic stability, which provides an important reference for the aeroelastic design of wind turbines.