Videogrammetry Dynamics Measurements of a Lightweight Flexible Wing in a Wind Tunnel

Abstract

Videogrammetry is a measurement technique well suited to characterizing lightweight, flexible wings in wind-tunnel testing. It is noncontact, full field, and can capture the large-amplitude deflections experienced by the wings. Here videogrammetry is used to analyze the spectral content of the motion of a flexible Nighthawk mini-unmanned aerial vehicle wing and animate the operating deflection shapes of the wing corresponding to structural resonance frequencies. The wing was tested at angles of attack ranging from ―5 to 13 deg and wind speeds ranging from 20 to 40 mph. Results show that the flexible wing tends to experience flapping behavior at frequencies much lower than structural resonance at low angles of attack. This behavior is confirmed by the spectral content of the wing displacements and the corresponding animated deflection shapes. This analysis uses videogrammetry data in the spectral analysis and visualization of resonance shapes. The data are necessary to validate numerical models of the wings, understand complicated membrane-structure interactions, and optimize wing performance in different flight regimes.