Oil-Flow Visualization on a SWT-2.3-101 Wind turbine

This paper describes flow visualization results from a continuing Cooperative Research and Development Agreement (CRADA) project between Siemens and the National Renewable Energy Laboratory (NREL) - National Wind Technology Center (NWTC). The cooperative research project was established for the purpose of advancing the understanding of wind turbine aerodynamics in the field environment with complex inflows resulting from atmospheric boundary layer conditions. The research includes extensive measurements to characterize the inflow to the turbine, blade aerodynamics, and loading on the blades, tower, and foundation of the turbine. Together in combination with regular turbine parameters such as power and generator speed the measurements will serve to provide a complete dataset for analyzing complete system performance as well as validation for improving rotor design models developed by Siemens and the NWTC. As a part of the overall research goals of the project, oil-flow visualization tests were conducted for the purpose of evaluating surface flow conditions and the effect of different vortex generators (VGs) at various blade pitch settings. The resulting flow patterns are used to correlate the flow separation on the blade surface to the estimated local angles of attack. Additionally, the results clearly indicate the effectiveness of vortex generators (VG) in delaying the occurrence of stall, compared to regions on the blade where no VG's are used.