Force measurements and flow visualization for a flexible flapping wing mechanism

This paper describes follow on efforts from a previously published paper on the development of a flapping wing mechanism. In this study additional force measurements were made and visualization of the flow over the flapping wings was conducted at selected conditions. The aerodynamic forces generated by flexible membrane type wings were measured using a two degree of freedom force balance constructed during the course of these experiments which measured the aerodynamic forces of lift and thrust. Lift and thrust measurements were acquired as the mechanism flapped the flexible wings for multiple cases, and the two most interesting conditions were explored in more detail. These two conditions consisted of a zero velocity free stream condition and a forward flight condition of 5 m/s. For these two conditions, high-speed video of the flapping wing was taken. The images from the video were also correlated with cycle averaged aerodynamic forces produced by the mechanism. Several observations were made regarding the behavior of flexible flapping wings that should aid in the design of future flexible flapping wing vehicles. In addition, flow visualization images were taken of the flapping wing under forward flight condition and flow field velocity vectors were calculated. This data was in turn used in an attempt to better understand the fluid dynamics behind the measured lift and thrust production during flapping.