Three dimensional simulation of J-shaped Darrieus vertical axis wind turbine

Abstract

The present research aims to investigate the concept of J-shaped blade in a straight–bladed Darrieus type VAWT in terms of output torque and power by employing high-fidelity 3D numerical simulations. Theoretically, since the J-shaped blades can benefit from the lift and drag forces simultaneously, this combined forces help the turbine possess faster operation at low wind speeds, thereby resulting in the termination of self-starting problem and improving power coefficients, especially at low and moderate tip speed ratios. In this study, NACA0015 is served as the base airfoil and has been modified to generate the desired J-shape profile. The attained results indicate improvements on torque and power coefficients, more specifically in the first half of revolution namely 0° < θ < 180°. Additionally, the amplitude of power and torque oscillation in each revolution has been curtailed and shifted up. A chunk of these improvements can be attributed to the inherent geometry of J-shaped profile through which the generated vorticities are trapped inside the blade and released behind the rotor. Not only that, the volumetric representation of turbulent kinetic energy discloses that the wake region behind the J-shaped rotor is free from slow dissipation of vorticities and possesses much less turbulency.