| A comprehensive experimental program has been conducted on a LS(1)-0421MOD airfoil model in the 3' x 5 ' OSU subsonic wind tunnel. Surface pressure distributions were obtained for 2D baseline and 3D configurations under clean and surface grit conditions. Several vortex generator configurations were evaluated. The data were taken for steady state and unsteady conditions. The steady state data included angles of attack from 0° to 30° and Reynolds numbers of 1.0 million. The unsteady conditions were simulated using a face cam that provided a sinusoidal angle of attack variation with 10° amplitude for three frequencies of 0.6 and 1.8 Hz at mean angles of attack of 8°, 14° and 20°. Surface pressure data were obtained from six spanwise stations, which were integrated to local coefficients. The maximum 2D lift coefficient obtained for the 1.0 million Reynolds number was 1.58 at 14.4° angle of attack. For the 3D case the maximum lift coefficient at the wall was 1.58 at 19.5° and at the tip was 1.20 at 18.3°. The results showed that the application of the grit roughness reduces the maximum lift coefficients in all configurations by as much as 50%.; The Flat and Curled vortex generators increased the maximum lift coefficient for both the 3D tip and wall stations, up to 1.6 and 1.92, respectively. The application of the vortex generators shifted the stall angle of attack by approximately 30%. A gritted model with the vortex generators saw an increase in both the maximum lift and stall angle of attack by approximately 25% in comparison to grit only.; The unsteady maximum lift coefficients were always higher than those for the steady state up to 60% and showed, generally, large hysteresis loops. The hysteresis loops were smaller for the 3D wing configuration due to the tip vortex influence, therefore smallest hysteresis loops occurred at the tip. The Flat and Curled vortex generators removed the hysteresis loops for all frequencies at 14° mean angle and significantly reduced the minimum value of the pitching moment and the pressure drag at stall. |
