Study on the Effect of Pitch Angle on the Aerodynamic Characteristics of a Vertical Axis Wind Turbine with a Dimple-Gurney Flap

Vertical axis wind turbine (VAWT) faces aerodynamic efficiency challenges due to dynamic stall and flow separation. This study investigates the combined optimization of a toward-outside dimple-Gurney flap (TO-DGF) and pitch angle to enhance the aerodynamic performance of a NACA0021 three-blade VAWT. We analyzed aerodynamic performance and flow field structures under varying pitch angles using large eddy simulations based on the lattice Boltzmann method. The baseline VAWT and TO-DGF VAWT achieve optimal performance at pitch angles of β = +8° and β = +6°, respectively, improving efficiency by 5.35% and 4.56% compared to β = 0°. TO-DGF induces Kármán vortex shedding to guide suction surface flow, while pitch angle adjustment optimizes the angle of attack, delaying dynamic stall. At a tip speed ratio of 2.4, the optimized TO-DGF VAWT increases wind energy utilization by up to 7.78%.