title: Effect of flexural and torsional wing flexibility on lift generation in hoverfly flight.
abstract: The effect of wing flexibility in hoverflies was investigated using an at-scale mechanical model. Unlike dynamically-scaled models, an at-scale model can include all phenomena related to motion and deformation of the wing during flapping. For this purpose, an at-scale polymer wing mimicking a hoverfly was fabricated using a custom micromolding process. The wing has venation and corrugation profiles which mimic those of a hoverfly wing and the measured flexural stiffness of the artificial wing is comparable to that of the natural wing. To emulate the torsional flexibility at the wing-body joint, a discrete flexure hinge was created. A range of flexure stiffnesses was chosen to match the torsional stiffness of pronation and supination in a hoverfly wing. The polymer wing was compared with a rigid, flat, carbon-fiber wing using a flapping mechanism driven by a piezoelectric actuator. Both wings exhibited passive rotation around the wing hinge; however, these rotations were reduced in the case of the compliant polymer wing due to chordwise deformations during flapping which caused a reduced effective angle of attack. Maximum lift was achieved when the stiffness of the hinge was similar to that of a hoverfly in both wing cases and the magnitude of measured lift is sufficient for hovering; the maximum lift achieved by the single polymer and carbon-fiber wings was 5.9 × 10(2)( )μN and 6.9 × 10(2)( )μN, respectively. These results suggest that hoverflies could exploit intrinsic compliances to generate desired motions of the wing and that, for the same flapping motions, a rigid wing could be more suitable for producing large lift.
authors.affiliation: School of Engineering and Applied Sciences, Harvard University, Cambridge, MA 02138, USA.
authors.forename: Hiroto
authors.initials: H
authors.lastname: Tanaka
authors.forename: John P
authors.initials: JP
authors.lastname: Whitney
authors.forename: Robert J
authors.initials: RJ
authors.lastname: Wood
mesh_terms: D000818:Animals; D001696:Biomechanical Phenomena; D002244:Carbon; D000077482:Carbon Fiber; D004175:Diptera / Q000502:physiology*; D005426:Flight, Animal; D008953:Models, Anatomic; D018583:Pliability; D014921:Wings, Animal / Q000033:anatomy & histology / Q000502:physiology*
chemical_list: D000077482:Carbon Fiber; D002244:Carbon