Large-eddy simulations of turbulent wake flows behind helical- and straight-bladed vertical axis wind turbines rotating at low tip speed ratios

We use large-eddy simulations to study the effects of helical-shaped blades on the wake flow characteristics of vertical axis wind turbines (VAWTs) at low tip speed ratios. Compared with the straight-bladed VAWT, our study shows that the helical-bladed VAWT generates near-wake flow structures with more three-dimensional features, which accelerate the wake transition to turbulence, enhance the small-scale turbulent dissipation, and result in a more rapid decay of the wake turbulence intensity. Moreover, the helical-bladed VAWT also exhibits much smaller temporal variations for the torque and power coefficients than the straight-bladed VAWT, resulting in smoother wind power generation.