Flycatchers boost lift by Leading Edge Vortex

In a new study, published online today (14 March 2012) in Biology Letters, our lab shows that the high-lift mechanism Leading Edge Vortex (LEV) appear to be common to most animal flyers, as it appears in slow flying pied flycatchers. These birds hover and fly slowly when foraging on aerial insects, and they have a powerful downstroke when the LEV boost the lift by 100%. This is much stronger than found in for example hummingbirds, but that could be explained by the fact that the flycatcher has a feathered (inactive) upstroke. As flycatchers catch insects they need to be equally good at maneuvering in the air, and the LEV helps them to achieve the required turn radii. This mechanism was thought to be restricted to insects, as it was key to explaining why e.g. a bumblebee can fly, and subsequently our group has found this in slowly flying bats. Now, we extend the set of animas using LEV in slow flight to include also normal hoverers (i.e. animals having an inclined stroke plane and inactive back-/upstroke) in this spectacular study.

New publication in French Academy journal

In a new paper published in the French Academy of Science journal, Comptes Rendus Mechanique, members of the Lund Animal Flight Lab has published a paper about a bat-inspired flapper (see figure). The paper is entitled "Stroke plane angle controls leading edge vortex in a bat-inspired flapper", This is an attempt to mimic the flight of a true bat, and how a wing composed of a compliant membranous surface function. The advantage of working with a flapper is that it can be programmed to move its wings in all possible ways, i.e. also in ways that live bats usually don't do, and so the whole kinematic parameter space can be explored. The drawback is of course ,as with all models, to know how much the model depart in performance from the real system and if it matters. The current paper describes the development of a leading edge vortex (LEV) during the downstroke, which is an important aerodynamic ingredient of slow bat flight. The LEV dynamics was partially controlled by the stroke plane angle. A copy of the paper can be obtain my mailing (anders.hedenstrom@biol.lu.se)