Numerical investigation on aerodynamic performance of vertical axis wind turbine based on cycloidal pitch control strategy

To address the inherent limitations of fixed-pitch VAWTs (vertical axis wind turbines), particularly the aerodynamic efficiency degradation caused by dynamic stall effects, this study proposes a novel active flow control methodology termed CPCS (cycloidal pitch control strategy). The investigation employs a National Advisory Committee for Aeronautics 0021 airfoil (NACA0021) symmetric airfoil-based aerodynamic model, utilizing unsteady Reynolds-averaged Navier–Stokes equations coupled with the shear stress transport k-ω turbulence model to resolve complex flow phenomena. Through systematic parametric analysis, the correlation between eccentricity ratio and energy harvesting characteristics was quantitatively established, with particular emphasis on vortex evolution mechanisms. Numerical results demonstrate that CPCS implementation effectively enhances the Cp (power coefficient) in the low tip speed ratio region, achieving a maximum Cp improvement of 6.8% compared to conventional fixed-pitch VAWT. This performance enhancement is primarily attributed to the torque amplification effect resulting from the dynamic optimization of attack angles in the downwind region of the blade.