Flapping Wing Deformation Measurement in Hover Flight Conditions

Abstract

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Deformation during the flapping cycle can be used as a determinant of hover-mode performance. The wing used here is a small hummingbird sized wing constructed from carbon fiber and machined acetal plastic. Digital image correlation measurements while the wing was flapped at 25 Hz is compared with aerodynamic thrust performance to reveal characteristics that might translate to favorable or poor wing performance. This is aimed to provide flapping micro air vehicle designers with knowledge of how to tailor their wings for desired aerodynamic performance. Three different wing designs were tested; all of which were the same planform area and tested using a single active degree of freedom flapping mechanism. Tip deflection and twist angle at 50 % and 75 % are extracted from the full-field deformation and used as metrics. The twist measurements showed advanced rotation in all the wings tested, though to different extents. The wing which had the most advanced rotation was also found to have produced the most thrust at 25 Hz, while the wing with the least tip deflection and was most efficient. This suggests that the larger tip deflection seen with the other wings may be detrimental to the efficiency of the wing.