Parameters affecting dynamic stall control by oscillatory excitation

A parametric study was undertaken to investigate the effect of oscillatory excitation (with zero net mass-flux) on a NACA 0015 airfoil, undergoing pitch oscillations at.. rotorcraft reduced frequencies. The primary objective of the study was to maximize airfoil performance while simultaneously limiting moment excursions to typical pre-stalled conditions, The incidence angle excursions were limited to ±5°. A “wide range reduced excitation frequencies., and. amplitudes were, considered for 0.3×10⁶≤Re≤0.9×10⁶ with various flap deflections and excitation, locations. Both light- and deep-stall were effectively controlled by the excitation whose effects were more pronounced at higher airfoil oscillation-rates and were effectively independent of Reynolds, number. As in the previous study, oscillatory excitation was found to be far superior to steady blowing, which was even detrimental under certain conditions. Flap-shoulder excitation was found to be superior to leading-edge excitation - particularly when used in conjunction with positive flap-deflection.