Numerical study of turbulent wake flows behind a helical-blade vertical axis wind turbine*

Vertical axis wind turbine (VAWT) has been widely used as a renewable energy harvesting device. The turbulent wake flow characteristics behind VAWTs with straight blades have been well studied over the past decades, which have provided valuable insights to help improve their performance in energy harvesting when used individually or in an array configuration. In comparison, there have been much fewer studies on the wake flow dynamics of VAWTs with helical-shaped blades. In this talk, the characteristics of turbulent wake flow behind the helical-blade and straight-blade VAWTs are studied using a large-eddy simulation (LES) model of wind turbulence combined with an actuator-line model of VAWTs. In particular, small helical and straight 5-blade VAWTs rotating at a low tip-speed ratio (~0.3) are considered, which are suitable for small-scale residential applications. The simulation results show that the wake flow behind the helical-blade VAWT exhibits considerable three-dimensional structures than that behind the straight-blade VAWT, resulting in noticeable differences in the turbulent flow characteristics and the wake speed recovery.