В«В lessДЄn experimental program to measure the aerodynamic performance of a NACA 64-621 airfoil with a truncated trailing edge for wind turbine applications has been conducted in the Ohio State University Aeronautical and Astronautical Research Laboratory 6 in. Good correlation was obtained between the results of the two different experimental methods for angles of attack from -4/degree/ to 36/degree/ and aileron deflections from 0/degree/ to 90/degree/. Lift coefficients were obtained by integrating pressures, and corrections were made for the three-dimensional effects of blade twist and downwash in the blade tip section. A belt containing 29 pressure taps was fixed to the full-scale section at midspan to obtain surface pressure data. The model airfoil contained 61 pressure taps connected by moreВ В» embedded tubes to pressure transducers. High Reynolds Number Wind Tunnel the full-scale blade section was tested in the NASA Langley Research Center 30- by 60-Ft Subsonic Wind Tunnel. The model airfoil was tested in the OSU 6- by 12-In. The airfoils were NACA 64-621 sections, including trailing-edge ailerons with a width equal to 38 percent of the airfoil chord. chord) was evaluated by comparing selected pressure distributions around the geometrically similar cross sections. chord) wind tunnel model and a full-scale wind turbine blade (24-ft tip section with a 36-in. The aerodynamic similarity between a small (4-in. Significantly, it also provided chord Reynolds numbers up to 2.0 million. To realistically satisfy these conditions the 7 x 10 offered a tunnel-height-to-model-chord ratio of 6.7, suggesting low interference effects even at the relatively high lift and drag conditions expected during the test.

Results of force and pitching moment measurements over the angle of attack range for all combinations of Reynolds numbers, thickness, and aspect ratios, and the effects of boundary layer tripping are =, applications of leading edge grit roughness (LEGR), and use of vortex generators (VGs), all at chord Reynolds numbers as high as possible for the particular model configuration. The aspect ratios were 6, 9, 12 and infinity. The thickness ratios studied were 0.18, 0.15, and 0.12, and 0.09. Tests were conducted at Reynolds number ranging from 0.25 x 106 to 1.0 x 106. This report documents results of the wind tunnel investigation of constant chord blades having four aspect ratios, with NACA 44XX series airfoil sections, at angles of attack ranging from -10/sup 0/ to 110/sup 0/.

The purpose of this wind tunnel study is to characterize the performance characteristics of a blade in stall as a function of its aspect ratio, airfoil thickness, and Reynolds number. Peak power predictions upon which wind turbine components are sized depend on a good understanding of a blade's post-stall characteristics. Unlike aircraft, a wind turbine's angle of attach range extends deep into stall where the three-dimensional performance characteristics of airfoils are not generally known. Wind turbine blades operate over a wide angle of attach range.

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