Meeting Abstract
Wing morphing allows birds to modify their aerodynamic performance and stability in flight, mediating the effects of fluctuating environmental conditions. Morphing is achieved through manipulation of the elbow and wrist joints, resulting in wing shape changes. Although previous research has shown that wrist flexion, manifested as sweep, improves high-speed and turning performance, there is no quantitative evidence demonstrating the effect of elbow angle on performance or stability. Further, for gliding flight, little information exists linking environmental turbulence, wing morphing characteristics, and aerodynamic parameters. To approach these questions, we first observed gulls in gliding flight and quantified their wing shapes. We, next, used cadavers to determine the range of elbow angles and the subset of angles used in glides. Finally, we evaluated the aerodynamic consequences of morphing configurations by preparing gull wings at different elbow angles, which were tested in a wind tunnel at varied turbulence intensities. We found evidence that elbow angle has a direct effect on aerodynamic efficiency, pitching stability, adverse yaw and the zero-lift pitching moment of the wing. This indicates that through elbow deflection alone, birds are capable of altering their glide performance and stabilization. Turbulence intensity affected aerodynamic efficiency and zero-lift pitching moment and additionally, maximal lift production. Relating the experimental results back to the morphed shapes used in gliding flight, we can identify a suite of aerodynamic benefits used by gliding gulls, and define how this is affected by a turbulent environment.
