Effect of blade-to-blade wake interference on aerodynamic performance of darrieus vertical axis wind turbines

Abstract

This study employs two-dimensional numerical simulations to systematically evaluate the effects of blade number and solidity on the power coefficient and unsteady flow characteristics of H-type Darrieus vertical axis wind turbines (VAWTs). Although conventional VAWTs designs typically adopt three or more blades, the results indicate that even under optimal tip-speed ratio conditions, such multi-blade configurations exhibit relatively low power coefficients. Through detailed analysis of velocity, vorticity, and turbulence intensity fields, the mechanisms underlying torque fluctuations, wake interactions, and blade load distributions are elucidated. The findings reveal that although the single-blade configuration achieves the highest power coefficient, exceeding the two-blade design by 3.6 %, it suffers from significant torque fluctuations that impair operational stability. In contrast, the two-blade VAWT offers an optimal balance, delivering a power coefficient 1.6 % higher than conventional three-blade designs, along with lower peak turbulence intensity and faster flow recovery within the rotor. Crucially, multi-blade configurations (3–5 blades) experience severe wake interference. As the number of blades increases, the vortex shedding frequency rises markedly, and cumulative wake effects lead to delayed flow recovery, resulting in a 7.2 % reduction in power coefficient. Furthermore, each blade number corresponds to a distinct optimal solidity value. While reducing the number of blades enhances instantaneous energy capture efficiency, increasing the blade count improves torque stability at the cost of greater wake losses. These insights provide new perspectives on rotor optimization for VAWTs and offer valuable guidance for the future design of vertical axis wind turbines.