عنوان مقاله [English]
Boundary layer profile on the upper surface of a super-critical airfoil in pitching motion has been experimentally investigated. Measurements were performed using a boundary layer having total pressure slim tubes positioned at 25% of the chord from the leading edge on the upper surface. In the static mode, the effect of the angle of attack ranging from -3 to 14 degrees and for free-stream velocities of 40 m/s to 70 m/s were investigated, where for the dynamic case effects of oscillation amplitude varied between $pm 3$ and $pm 10$ degrees, reduced frequencies from 0.007 to 0.0313, and mean angles of attack between -3 and 6 degrees, on the boundary layer profile were studied for one oscillation cycle. Time series of each pressure signals acquired from the pressure sensors were processed after filtering and corrections. To study the amplitude of the dominated frequency in the velocity profile, Fast Fourier Transformation on the pressure signals acquired from each rake was used. The results indicate hysteresis loops for boundary layer thickness during upstroke and downstroke states and extension of width of hysteresis loops at higher reduced frequency. In addition, boundary layer thickness is decreased as the angle of attack is increased in the upstroke portion of the motion.