Dynamic stall control by periodic excitation, Part 1: NACA 0015 parametric study

A parametric study was undertaken to investigate the effect of periodic excitation (with zero net mass flux) on a NACA 0015 airfoil undergoing pitch oscillations at rotorcraft reduced frequencies under incompressible conditions. The primary objective of the study was to maximize airfoil performance while limiting moment excursions to typical prestalled conditions. The incidence angle excursions were limited to ±5 deg, and a wide range of reduced excitation frequencies and amplitudes were considered for 0.3 × 10⁶ ≤ Re ≤ 0.9 × 10⁶ with various flap deflections an excitation locations. Significant increases in maximum lift and reductions in drag were attained while containing the moment excursions. Oscillatory excitation was found to be far superior to steady blowing, which was even detrimental under certain conditions, and flap-shoulder excitation was found to be superior to leading-edge excitation.