title: Lift vs. drag based mechanisms for vertical force production in the smallest flying insects.
abstract: We used computational fluid dynamics to determine whether lift- or drag-based mechanisms generate the most vertical force in the flight of the smallest insects. These insects fly at Re on the order of 4-60 where viscous effects are significant. Detailed quantitative data on the wing kinematics of the smallest insects is not available, and as a result both drag- and lift-based strategies have been suggested as the mechanisms by which these insects stay aloft. We used the immersed boundary method to solve the fully-coupled fluid-structure interaction problem of a flexible wing immersed in a two-dimensional viscous fluid to compare three idealized hovering kinematics: a drag-based stroke in the vertical plane, a lift-based stroke in the horizontal plane, and a hybrid stroke on a tilted plane. Our results suggest that at higher Re, a lift-based strategy produces more vertical force than a drag-based strategy. At the Re pertinent to small insect hovering, however, there is little difference in performance between the two strategies. A drag-based mechanism of flight could produce more vertical force than a lift-based mechanism for insects at Re<5; however, we are unaware of active fliers at this scale.
authors: Department of Mathematics, University of North Carolina, Chapel Hill, NC 27599, USA. Electronic address: skjohnsn@email.unc.edu.
authors: S K
authors: SK
authors: Jones
authors: Department of Mathematics, University of North Carolina, Chapel Hill, NC 27599, USA.
authors: R
authors: R
authors: Laurenza
authors: Department of Biology, University of North Carolina, Chapel Hill, NC 27599, USA.
authors: T L
authors: TL
authors: Hedrick
authors: Department of Mathematics, University of North Carolina, Chapel Hill, NC 27599, USA.
authors: B E
authors: BE
authors: Griffith
authors: Department of Mathematics, University of North Carolina, Chapel Hill, NC 27599, USA; Department of Biology, University of North Carolina, Chapel Hill, NC 27599, USA.
authors: L A
authors: LA
authors: Miller
mesh_terms: D000465:Algorithms; D000818:Animals; D001696:Biomechanical Phenomena; D005426:Flight, Animal / Q000502:physiology*; D057446:Hydrodynamics; D007313:Insecta / Q000502:physiology*; D008954:Models, Biological; D014921:Wings, Animal / Q000502:physiology*
keywords: Biomechanics; Computational fluid dynamics; Immersed boundary method; Insect flight