Roughness and turbulence effects on the aerodynamic effciency of a wind turbine blade section

Numerous experiments were conducted on the section of a 660 kw wind turbine blade in a subsonic wind tunnel. The selected airfoil was tested with a clean and distributed contamination roughness surface, with a high and low tunnel turbulence intensity. Surface contamination was simulated by applying 0.5 mm height roughness over the entire upper surface of the airfoil. The surface pressure distribution is measured under a steady and unsteady condition, at three Reynolds numbers; 0.43, 0.85, and 1.3 million, and over a range of angles of attack, AOA=7-19. Unsteady data were acquired by both pitch and plunge-type oscillation of the model about its quarter chord at a reduced frequency of 0.07. Results show that the surface roughness reduces section aerodynamic eciency and the lift coecient, but increases the drag coecient for all Reynolds numbers. The application of roughness reduces the upper surface pressure coecient and extends a separation region at high angles of attack. Increasing the tunnel turbulence intensity resulted in delay of the stall, an increase of maximum lift coecient, and smoothness of stall behavior. However, the drag coecient increased signicantly. Furthermore, turbulence intensity aected the predicted power output of the blade.