Experimental Investigation of Suddenly Stop of Supercritical Airfoil SC-0410 between Pitching Motion

In this research, the aerodynamic behavior and the time lag of supercritical airfoil SC-0410 undergoing a classic maneuver were investigated. This maneuver consist of pitch-up motion, pause and then pitch-down motion. In this research, the effect of reduced frequency and stop duration were investigated. The experiments were conducted in a subsonic close return wind tunnel with test section dimensions of 0.8 m×0.8 m. A pitching motion was produced by oscillation system about the quarter cord axis at reduced frequency of 0.01 to 0.12. In this study, both the mean angle of attack and oscillation domain were constant. The stop occurs between the upstroke motions. The stop angle of 5 degrees, was smaller than the static stall angle. Immediately after upstroke motion, suddenly stop and down stroke motion, the flow field is not achieved the static condition and the time lasts that the changes of 3 stages pass the flow field about airfoil and gain to initial steady state condition. The results show that reduced frequency was major parameter on the time lag. While the measured time lag was not sensitive to the pause duration. By increasing the reduced frequency, the time lag decreases because of large amount of energy dissipation at high frequencies. It was worth to point that the aerodynamic coefficient diagram verses angle of attack forms the hysteresis loop at unsteady stream. The hysteresis loop is the result of phase difference between the motion and the flow field.