Aerodynamic Characteristics of a Pitching Airfoil Through Pressure-Distortion Correction in Pneumatic Tubing

Abstract

The lift and pressure-drag coefficients integrated from unsteady-pressure coefficients are investigated for a pitching airfoil at a low Reynolds number. The unsteady pressure on the pitching-airfoil surface is measured through pressure-distortion correction in the pneumatic tubing, and the pressure-distortion characteristics are estimated. The unsteady pressure on the pitching airfoil is significantly delayed with reduced frequency, and the nondimensional time delay is evaluated with respect to unsteady pressure. The hysteresis loops of the lift and pressure-drag coefficients rotate in counterclockwise and clockwise directions, respectively, and this is due to the reattachment during downstroke. Moreover, the angle of attack range, in which aerodynamic performance is nonlinearly varied, is generated due to the nonlinear boundary-layer behavior caused by the low-Reynolds-number effect. As a result, the unsteady aerodynamic characteristics at are dominantly influenced by the reattachment and the low-Reynolds-number effect.