03 March 2011
A new paper, entitled Comparative aerodynamic performance of flapping flight in two bat species using time-resolved wake visualization from the lab was published today in the Journal of the Royal Society Interface, in which Florian Muijres and co-workers compare two species of bat with regard to their aerodynamic performance. Florian has developed very detailed methods for analyzing the wake properties, as recorded by time-resolved stereo PIV in the Lund University wind tunnel. The two species being compared, Glossophaga soricina and Leptopnycteris yerbabuenae, differ with a factor of 2 in mass and in some ecological respects. The Leptonycteris is a migrant while the Glossophaga is a resident, while they are both fruigivores that eat/drink nectar from plants using hovering flight. A measure of flight economics, the maximum lift to drag, was similar between the species, but it occurred at a higher speed in the larger species. This could reflect different performance optima between the two species associated with requirements for slow flight in Glossophaga and cruising/migratory flight in Leptonycteris. The wake geometry showed the typical bat features in both species, including reversed vortex loops at the transition between up-/downstroke and vortices shed from the wing roots.