Measurement of unsteady transition on a pitching airfoil using dynamic pressure sensors

Abstract

Unsteady boundary layer transition on a pitching OA209 airfoil in a wind tunnel was detected by using pressure fluctuation measurement at different oscillation frequency. Thirty Kulite dynamic pressure transducers flush-mounted on the airfoil surface recorded pressure signatures, and root mean square of pressure signatures were calculated. Results indicated that the criterion of transition for static airfoil defined as the peak of root mean square of pressure fluctuation was still suitable for detection of transition on a pitching airfoil. Fixed transition experiment for pitching airfoil was performed to validate the conclusion. Effect of oscillation frequency on transition was investigated. For small reduced frequency, the hysteresis loop is larger near leading edge. With increasing in the oscillation frequencies, the transition was promoted and relaminarization was enhanced.