title: Vortex interaction of tandem pitching and plunging plates: a two-dimensional model of hovering dragonfly-like flight.
abstract: The force evolution and associated vortex dynamics on a nominal two-dimensional tandem pitching and plunging configuration inspired by hovering dragonfly-like flight have been investigated experimentally using time-resolved particle image velocimetry. The aerodynamic forces acting on the flat plates have been determined using a classic control-volume approach, i.e. a momentum balance. It was found that only the tandem phasing of ψ = 90° was capable of generating similar levels of thrust when compared to the single-plate reference case. For this tandem configuration, however, a much more constant thrust generation was developed over the cycle. Further examination showed that the force and vortex development on the fore-plate was unaffected by the tandem configuration and that nearly all variations in performance could be attributed to the vortex interaction on the hind-plate. By calculating the trajectory and strength of the hind-plate's trailing-edge vortex, the chain-like vortex interaction mechanism responsible for improved performance at ψ = 90° could be identified. The underlying result from this study suggests that the dominant vortex interaction in dragonfly flight is two dimensional and that the spanwise flow generated by root-flapping kinematics is not entirely necessary for efficient propulsion but potentially due to evolutionary restrictions in nature.
authors.affiliation: Institute of Fluid Mechanics and Aerodynamics, Technische Universität Darmstadt, Germany. derival@ucalgary.ca
authors.forename: David
authors.initials: D
authors.lastname: Rival
authors.forename: Dirk
authors.initials: D
authors.lastname: Schönweitz
authors.forename: Cameron
authors.initials: C
authors.lastname: Tropea
mesh_terms: D000818:Animals; D032701:Biomimetics / Q000379:methods*; D003198:Computer Simulation; D005426:Flight, Animal / Q000502:physiology*; D007313:Insecta / Q000502:physiology*; D008954:Models, Biological; D017711:Nonlinear Dynamics; D014921:Wings, Animal / Q000502:physiology*