Aerodynamics of flapping wings in forward flight
Final Report Abstract
Under this project, the applicant investigated the aerodynamic characteristics of a leadingedge vortex (LEV) of flapping plates in freestream. By using the wind tunnel B of the Chair of Aerodynamics and Fluid Mechanics at the Technical University of Munich, effects of an advance ratio, aspect ratio, sweptback angle, and pitching angle of flapping plates on the LEV have been explored in detail. During 25 months of support, the applicant succeeded to build a sophisticated testbed including a robotic arm that can give multiple degrees of freedom in designated wingbeat frequency at high temporal accuracy. An in-house force/torque transducer that can collect a micro force at a relatively large torque was also developed. These systems were controlled by an in-house program written in LabVIEW™. The technique that can remove an inertial and gravitational force from measured values, which are inevitably included in addition to the aerodynamic force, was proposed and implemented. The PI further did an international collaboration with Korea Advanced Institute of Science and Technology (KAIST) in South Korea during the research period, which equips a water-towing tank facility exclusively built for moving objects in freestream. Based on this effort, we managed to reveal some characteristics of the LEV. 1) the spanwise flow progressing from the wingroot to the wingtip with a sweptback angle also maintains the LEV only up to almost three times the chord, as it had been found in a revolving/flapping wing. 2) the sweptback angle of the wing in a wingbeat motion results in a time-varying increment in an aerodynamic force during the stroke even it moves with a constant stroke velocity. 3) combination of the two sources of spanwise flow does not give noticeable changes in the LEV, and still has certain optimum values. These new findings have been reported in two peerreviewed journal papers, one international conference, and one workshop for aerodynamic engineers.
Publications
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Aerodynamic investigation on shifted-back vertical stroke plane of flapping wing in forward flight. Bioinspiration & Biomimetics, 16(6), 064001.
Han, Jong-Seob & Breitsamter, Christian
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Leading-Edge Vortex Characteristics of Low-Aspect-Ratio Sweptback Plates at Low Reynolds Number. Applied Sciences, 11(6), 2450.
Han, Jong-Seob & Breitsamter, Christian
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“Aerodynamics of Low-Aspect-Ratio Flapping Plates in Forward Flight,” STAB Workshop, 16-17 November 2021, Goettingen, Germany.
Jong-Seob Han & Christian Breitsamter
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“Wind-tunnel test on leading-edge vortex of low-aspect-ratio flapping plates,” 33rd Congress of the International Council of the Aeronautical Science (ICAS 2022), September 4-9, Stockholm, Sweden.
Jong-Seob Han & Christian Breitsamter
