Aerodynamic experimental investigation and analysis of the flow and thrust generation of the flexible flat flapping wing robot

For micro unmanned aerial vehicles with the flapping wing mechanism, the thrust is produced by the unsteady aerodynamics. The produced flapping thrust is similar to the thrust created in nature. However, the aerodynamic flow of the bionic flapping wings and produced thrust relationship has not been truly investigated. This study has found the vortex locations behind the wings that affect the thrust at specific periods of the flapping cycle. The aerodynamic flow field around the flapping wingspan of 33 cm is visually observed and reported by the smoke wire technique. The leading edge and trailing edge vortexes are recorded with a high-speed VDO camera as well as the real-time produced thrust is acquired. It was found that the leading edge vortex occurs near the top wing surface at the 20-degree upstroke wing position, the trailing edge vortex occurs after the 20-degree down stroke and the maximum thrust occurs at the −5-degree down stroke. In addition, the leading and trailing edge vortexes are created beneath the wings during the upstroke and changed to be the jet flow generating the thrust. The produced thrust and flapping stroke relationship are analyzed in this study. The investigation provides the fundamental knowledge to design the flying robot body configuration that could help generating thrust in the desired direction.