In recent years, leading-edge protuberances have attracted plenty of attention as a passive method to manipulate flow separation on wind turbine blades. In this paper, an experimental investigation is carried out to explore the effect of leading-edge protuberances on the aerodynamic performance of wind turbine airfoils with and without surface roughness. A direct force measurement technique with the application of three-component balance is applied, and a hot-wire anemometer is used to measure the boundary layer flow to understand the governing mechanism for the flow regulation of the leading-edge protuberances. The current results confirm that the surface roughness leads to a decreased lift-to-drag ratio and an increased aerodynamic fluctuation of the baseline airfoil, which may cause severe losses in wind power capture. For the wavy airfoil, the leading-edge protuberance has facilitated the suppression of flow separation and the improvement of the airfoil aerodynamic performance in the poststall region. The results of the velocity measurement indicate that the leading-edge protuberances weaken the vortex shedding on the airfoil, which has a significant impact on the fluctuation of the aerodynamic force. For airfoils with a rough surface, the vortex shedding energy close to the trailing edge is evidently weakened for the wavy airfoil, which contributes effectively to the suppression of the shedding of the separated vortex and improve the stability of the aerodynamic force, compared to the baseline case. The effectiveness of leading-edge protuberances in the improvement of the performance stability may facilitate the service life of the blade and the ability of wind power capture.

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