Extracting Dynamic Loads from Optical Deformation Measurements

Abstract

*† ‡ The possibility of extracting dynamic force information from aerodynamic surfaces by means of non-intrusive measurements was investigated. A videogrammetry system was used to measure three-dimensional coordinates of multiple targets on three thin rectangular cantilever plates deforming under unsteady forces in a wind tunnel. The plates were excited into flutter modes in the Old Dominion University Low Speed Wind Tunnel and a new highspeed videogrammetry system developed for NASA Langley Research Center by High Technology Corporation was used to monitor deflections. Retro-reflective targets on the plates were tracked at an average rate of 160 frames per second. Deformation information was analyzed to estimate the aerodynamic forces acting on the plates during flutter. Results indicate that the method may be used successfully to recover unsteady aerodynamic forces. Considering a cantilever plate to be a simplistic version of an aircraft wing, this technique has potential applications in aircraft flight and wind tunnel testing.