Aerodynamic performance enhancement and noise reduction for Darrieus vertical axis wind turbines: V-shaped blades and trailing-edge serrations

The Darrieus vertical axis wind turbines (VAWTs) are one of the mainstream devices for wind energy utilization in the urban areas. The market's pursuit of high wind energy conversion efficiency promotes the research on improving the wind turbine power coefficient while reducing noise. This paper makes further investigation on the aerodynamics and aeroacoustics of a small VAWT with V-shaped blades and trailing-edge serrations. The feasibility of utilizing the Reynolds-Averaged Navier-Stokes SST k-omega turbulence model and the FW-H method is verified against experiments. The studied V-shaped blades can effectively improve the power performance of VAWT over a wide range of tip speed ratios under normal wind speed conditions, and the trailing-edge serrations will also slightly increase the power output of V-bladed VAWT at the optimal tip speed ratio. The power coefficient of the V-bladed wind turbine with trailing-edge serrations is about 28.3% higher than that of the original turbine. In addition, a dumbbell-shaped noise directivity distribution was first discovered in the VAWT compared with the traditional elliptical distribution. The V-bladed VAWT generated less low-frequency noise and the trailing-edge serrations realized the expected noise reduction effect. Practically, this study proposes a feasible solution for the design of high-efficiency and low-noise wind turbines.