Suppression of Dynamic Stall by Leading Edge Slat on a Darrieus Vertical Axis Wind Turbine

Abstract

The performance characteristics of vertical axis wind turbines are considerably influenced by dynamic stall phenomenon which is the processes of delayed flow separation caused by a rapid excursion in the angle of attack of rotating blades. It leads to a sudden drop in lift forces which further reduce the rotor power output and efficiency significantly. The present analysis is to explore the ideas for enhancing the performance and efficiency for a vertical axis wind turbine model by implementing leading-edge slat on blades of the turbine to delay flow separation. In this paper a comprehensive two-dimensional computational fluid dynamics study has been carried out on airfoil under transient pitch oscillating motion, to obtain detailed flow fields for analysis and flow visualization. The Reynolds Averaged Navier-Stokes K-omega shear stress transport model is used to predict turbulence during computations. In addition, a sliding mesh technique along with the user-defined function is used. The outcomes show that the improved design of the turbine with the leading edge slat not only increases the lift coefficient at low Reynolds number but also enhanced the capability of wind energy extraction compared baseline model. The flow separation was delayed by a certain degree due to the leading edge slat. Consequently, the proposed model is appropriate and it can be used various lifting objects, to enhance the output power and efficiency.