A Numerical Procedure for Variable-Pitch Law Formulation of Vertical-Axis Wind Turbines

Abstract

A numerical procedure was developed to determine a variable-pitch law that maximized the performance of a vertical-axis wind turbine (VAWT). The methodology was based on the determination, for each blade, of the angle of attack maximizing the stationary aerodynamic efficiency at prescribed azimuthal positions. The angles of attack were determined by means of a panel method with a low computational effort, and the methodology was implemented in Matlab® software (version R2021a) allowing us to achieve in real time a variable-pitch law suitable for the turbine geometry. The variable pitch law was validated by considering its effect on the torque of a 2D model of an H-Darrieus turbine. U-RANS analyses were carried out with a K−ωSST model and a sliding-mesh technique was used to prescribe the blade motion around the shaft and pitch motion. Results showed how the variable-pitch law delayed the dynamic stall and improved the aerodynamic performance considerably.