Drag reduction using riblet film applied to airfoils for wind turbines
This thesis presents results of a study to investigate the drag reduction properties of riblet film on airfoils specifically designed for wind turbine applications. The S809 and DU 96-W-180 airfoils were tested with four different symmetrical V-shaped riblet sizes (44, 62, 100 and 150 μm) at three Reynolds numbers (1, 1.5 and 1.85 million) and at angles of attack spanning the low drag range of the airfoils. The airfoil chord was 18 in (0.457 m). Tests were run with riblet film covering different chordwise extents of the airfoils in order to determine the optimal riblet location in terms of drag reduction. In addition to V-shaped riblets, skipped-tooth riblet configurations were also tested on the DU 96-W-180 airfoil. Results showed that the magnitude of drag reduction depended on the angle of attack, Reynolds number, riblet size, and riblet location and was highly airfoil specific. For some configurations, riblets produced significant drag reduction of up to 5%, while for others riblets were detrimental to airfoil performance and caused an increase in drag. While no clear trends were observed for riblets on the S809 airfoil, results from the DU 96-W-180 tests indicated an optimum riblet size of 62 μm for the range of Reynolds numbers at which tests were conducted. Results also showed that each riblet size performed best at a given Reynolds number with the optimal Reynolds number decreasing with an increase in riblet size.
Aerodynamics, airfoil, drag reduction, performance, riblet film, riblets, skin friction, skipped-tooth, wind tunnel, wind turbine
University of Illinois - Urbana-Champaign
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University of Illinois at Urbana-Champaign