Numerical and Experimental Assessment of a Passive Flow-Control Strategy for Vertical-Axis Wind Turbine Blades

Vertical-axis wind turbines are attractive for urban energy applications, but modest efficiency still constrains their wider use. This study evaluates a passive flow-control solution consisting of 45°-inclined cavities introduced on the suction side of a NACA0012 airfoil. Two configurations were investigated, a baseline rotor and with a modified rotor with cavities placed over the last two-thirds of the suction side. The CFD component used 2D transient ANSYS Fluent (Version 19.2) simulations with Dynamic Mesh and 6DOF to compare the aerodynamic rotor response. Numerically, the modified configuration reached higher angular velocity, tip speed ratio, power coefficient, and aerodynamic power than the baseline, with the advantage increasing at higher wind velocities. The experimental component used fabricated polycarbonate rotor models and directly measured rotational speed, voltage, and current in a generator–rectifier–load chain. Based on five repeated measurements, at 14 m/s the modified rotor delivered an average useful electrical power of 1.314 ± 0.016 W, compared with 0.940 ± 0.014 W for the baseline rotor, corresponding to an increase of 39.79% in useful power and 13.22% in tip speed ratio. The 2D CFD model reproduced the experimental performance ranking, despite overpredicting absolute power levels.