Aerodynamic damping derivatives of low aspect ratio wings at low Reynolds numbers

Abstract

This paper focuses on experimentally measuring the aerodynamic damping stability derivatives of a harmonically oscillating low aspect ratio (LAR) wing at a Reynolds number of 7.5× 10. Recent publications by the authors have demonstrated that the developing tip vortex asymmetry for an LAR wing in sideslip leads to a significant roll moment despite the lack of dihedral, sweep, fuselage interference or vertical tail surfaces, indicating that aerodynamic lateral damping may exist for pure flat plate wings. To date, the dearth of experimental data for LAR damping derivatives has prevented the formation of a dynamic model to be used in solving the equations of motion; to address this, a forced oscillation technique is implemented, described and validated for a wing with an aspect ratio of unity. Damping in yaw and pitch are reported for a variety of incidence angles (α and β) and frequencies of motion (f = [0.5, 1, 1.5, 2, 1.5 and 3]Hz); damping of normal force in pitch (CNF,q) is found to be the most significant derivative by at least an order of magnitude. The damping derivatives converge to near-constant values at mid to high range frequencies for all incidence angles, suggesting that constant values of the derivatives may potentially be implemented in linearized forms of the equations of motion during flight dynamics simulations.