title: Wake structure and kinematics in two insectivorous bats.
abstract: We compare kinematics and wake structure over a range of flight speeds (4.0-8.2 m s(-1)) for two bats that pursue insect prey aerially, Tadarida brasiliensis and Myotis velifer Body mass and wingspan are similar in these species, but M. velifer has broader wings and lower wing loading. By using high-speed videography and particle image velocimetry of steady flight in a wind tunnel, we show that three-dimensional kinematics and wake structure are similar in the two species at the higher speeds studied, but differ at lower speeds. At lower speeds, the two species show significant differences in mean angle of attack, body-wingtip distance and sweep angle. The distinct body vortex seen at low speed in T. brasiliensis and other bats studied to date is considerably weaker or absent in M. velifer We suggest that this could be influenced by morphology: (i) the narrower thorax in this species probably reduces the body-induced discontinuity in circulation between the two wings and (ii) the wing loading is lower, hence the lift coefficient required for weight support is lower. As a result, in M. velifer, there may be a decreased disruption in the lift generation between the body and the wing, and the strength of the characteristic root vortex is greatly diminished, both suggesting increased flight efficiency.This article is part of the themed issue 'Moving in a moving medium: new perspectives on flight'.
authors.affiliation: School of Engineering, Brown University, Providence, RI 02912, USA Structure and Motion Laboratory, Royal Veterinary College, Hatfield AL97TA, UK thubel@rvc.ac.uk.
authors.forename: Tatjana Y
authors.identifier: 0000-0002-6749-6747
authors.initials: TY
authors.lastname: Hubel
authors.affiliation: Department of Ecology and Evolutionary Biology, Brown University, Providence, RI 02912, USA Center for Design Innovation, Winston Salem, NC 27101-4019, USA.
authors.forename: Nickolay I
authors.initials: NI
authors.lastname: Hristov
authors.affiliation: School of Engineering, Brown University, Providence, RI 02912, USA Department of Ecology and Evolutionary Biology, Brown University, Providence, RI 02912, USA.
authors.forename: Sharon M
authors.initials: SM
authors.lastname: Swartz
authors.affiliation: School of Engineering, Brown University, Providence, RI 02912, USA Department of Ecology and Evolutionary Biology, Brown University, Providence, RI 02912, USA.
authors.forename: Kenneth S
authors.initials: KS
authors.lastname: Breuer
mesh_terms: D000818:Animals; D001696:Biomechanical Phenomena; D002685:Chiroptera / Q000033:anatomy & histology / Q000502:physiology*; D005426:Flight, Animal; D012212:Rheology; D014921:Wings, Animal / Q000033:anatomy & histology / Q000502:physiology*
keywords: bat flight; flapping flight; wake structure