Effect of surface contamination on the performance of a section of a wind turbine blade

A series of low speed wind tunnel tests were conducted on a section of a 660 kW wind turbine blade to examine the effects of distributed surface contamination on its performance characteristics. The selected airfoil was tested with a clean surface, two types of zigzag roughness, strip tape roughness and distributed contamination roughness. The straight and zigzag leading edge roughness models simplify the contamination results in an early turbulence transition. In this study, surface contamination was simulated by applying 0.5 mm height roughness over the entire upper surface of the airfoil. The distribution density varied from the leading edge to the trailing edge of the model. Our data show that this particular airfoil was very sensitive to surface contamination and its maximum lift coefficient decreased up to 35%, while the stall angle of attack increased slightly. The surface contamination, however, caused very smooth stall characteristics and less lift drop in the post stall region. In contrast to the clean model, the maximum lift coefficient of the roughened airfoil increased with Reynolds number. The effects of zigzag roughness and strip tape roughness were less than that of the distributed contamination roughness.