The main purpose of this study is to investigate the effects of adding endplates on J-shaped blades of the Darrieus Vertical Axis Wind Turbine (VAWT) to improve aerodynamic characteristics. For this purpose, three types of blade profiles for Darrieus VAWT, including conventional airfoil (NACA0015), J-NACA0015, and J-EP NACA0015 are studied. The J-shaped blade is a notched NACA0015 profile, which is designed by eliminating a fraction of the pressure side of the conventional airfoil from maximum thickness, and J-EP is the J-shaped blade with endplates. To analyze the effects of end-plates on aerodynamic performance, all important parameters such as torque and power coefficients, lift and drag coefficients, tangential and normal force coefficients, vorticity volumetric structures, and aeroacoustics are studied. Results indicate that end plates reduce tip leakage flow, resulting in a more effective conversion of wind energy, such that the J-EP blades increase the power coefficient by 4.88% and 10.23% in comparison with J and conventional blades at optimal TSR (TSR = 1.6), respectively. At low TSRs, the torque coefficient for J-EP is higher than that of J and conventional blades, so that the J-EP blades increase the torque coefficient by 10.42% and 122.42% in comparison with J and conventional blades at TSR = 0.6, respectively. This implies that the self-starting capability of the turbine with J-EP blades is higher than that of the J and conventional blades. The volumetric representation of vorticity indicates that the J-EP blade generates fewer and smaller vortices downstream in comparison with other blades. Also, J-EP decreases the wake region behind the rotor and leads to a reduction in turbulence and boosts the flow uniformity at the flow downstream. The sound emitted from the turbine is investigated using the FW-H acoustic analogy method. The results indicate that the sound pressure level for the turbine with J and J-EP blades is lower than that of the conventional blade.
Zamāni et al. (Mon,) studied this question.