title: Wing-kinematics measurement and aerodynamics in a small insect in hovering flight.
abstract: Wing-motion of hovering small fly Liriomyza sativae was measured using high-speed video and flows of the wings calculated numerically. The fly used high wingbeat frequency (≈265 Hz) and large stroke amplitude (≈182°); therefore, even if its wing-length (R) was small (R ≈ 1.4 mm), the mean velocity of wing reached ≈1.5 m/s, the same as that of an average-size insect (R ≈ 3 mm). But the Reynolds number (Re) of wing was still low (≈40), owing to the small wing-size. In increasing the stroke amplitude, the outer parts of the wings had a "clap and fling" motion. The mean-lift coefficient was high, ≈1.85, several times larger than that of a cruising airplane. The partial "clap and fling" motion increased the lift by ≈7%, compared with the case of no aerodynamic interaction between the wings. The fly mainly used the delayed stall mechanism to generate the high-lift. The lift-to-drag ratio is only 0.7 (for larger insects, Re being about 100 or higher, the ratio is 1-1.2); that is, although the small fly can produce enough lift to support its weight, it needs to overcome a larger drag to do so.
authors.affiliation: Institute of Fluid Mechanics, Beijing University of Aeronautics &Astronautics, Beijing 100191, China.
authors.forename: Xin
authors.initials: X
authors.lastname: Cheng
authors.affiliation: Institute of Fluid Mechanics, Beijing University of Aeronautics &Astronautics, Beijing 100191, China.
authors.forename: Mao
authors.initials: M
authors.lastname: Sun
mesh_terms: D000818:Animals; D001696:Biomechanical Phenomena; D004175:Diptera / Q000502:physiology*; D005426:Flight, Animal / Q000502:physiology*; D013997:Time Factors; D014921:Wings, Animal / Q000033:anatomy & histology / Q000502:physiology*