Aerodynamic analysis of a step adjustment method for blade pitch of a VAWT

Vertical-axis wind turbines (VAWTs), which are considered an important wind energy conversion device, have recently received renewed attention. Researchers are investigating the pitch angle control method to improve the wind energy utilization efficiency of VAWTs. In this study, ANSYS Fluent is used to investigate the aerodynamic performance of two-dimensional VAWTs. Different pitch angles are investigated using unsteady Reynolds-averaged Navier-Stokes calculations, and turbulence is modeled with the shear stress transport k-co model. Four quartiles are defined for the azimuthal angle of a rotation period: upwind (45 degrees < theta < 135 degrees), leeward (135 degrees < theta < 225 degrees), downwind (225 degrees < theta < 315 degrees), and windward (315 degrees < theta < 45 degrees). Furthermore, the sliding-mesh technique and a user-defined function are applied to adjust the pitch angle of the wind turbine blades in different azimuthal zones. This study proposes a pitch angle control method that effectively improves the efficiency of VAWTs by comprehensively analyzing the aerodynamic performance of the wind turbine and power coefficient (C-p) variation in each zone. The results indicate that an appropriate pitch angle control solution can significantly improve the efficiency of the wind turbine. Compared to a fixed pitch angle of 0 degrees, an approximately 17.0% increase in C-p can be achieved and, compared to the optimal fixed pitch angle -1 degrees, an approximately 12.0% increase in C-p can be achieved.