New paper about bat aerodynamics from Animal Flight Lab

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.

Animal Flight Research Highlighted in Research Council Annual Report

In the current "Annual Report for 2010" from the Swedish Research Council (VR), our research on animal flight was selected to illustrate "basic research of the highest quality", which is an investment in the future. It's very nice to be appreciated in this way, I think, by our main funding body and we should see that as a token of achieved quality and visibility. There is also some accompanying text on VR:s website, with answers to some questions about the research. The picture on the left was taken earlier this winter, when AH was performing some critical experiments.

Rhea gets PhD

On last Friday our group member Rhea von Busse passed her oral examination for a PhD at the Humboldt University, Berlin. Dr Busses thesis is about "The trinity of energy conservation: kinematics, aerodynamics and energetics of the lesser long-nosed bat (Leptonycteris yerbabuenae)", including chapters on kinematcs, aerodynamics (wakes), a comparison between kinematics and wakes, and an investigation about the flight metabolic rate. This thesis is the result of the collaboration between AFL and York Winter. The discussions leading up to this collaboration were initiated some 10 years ago, when AH visited the Max Planck Institute at Seewiesen to give a talk about the wind tunnel studies on birds that were underway. Then Rhea came with the first batch of Glossophaga soricinas used for our first studies (and Rheas master thesis). We congratulate Rhea to this magnificent achievement and wish her the best of luck with her new studies on bats in the Brown University bat biology group.

New wind tunnel at Western Ontario

In a NewsFocus piece in Science entitled "Treading Air", the new hypobaric wind tunnel at the University of Western Ontario is described. In this wind tunnel the temperature, air pressure and humidity can be controlled. This tunnel is therefore ideal for studying physiology during flight in way not possible in other wind tunnels. This tunnel is also equipped with a PIV-system, and the article tells that airflow around the wing-tips of a starling has been studied. We wish our wind tunnel colleagues at Western Ontario, led by Chris Guglielmo (see image), the best of luck with their wind tunnel and look forward to see their first results published soon.

Nature-inspired flight

In a new issue of the journal Bioinspiration & Biomimntics, a special section is devoted to nature-inspired flight. There is an emphasis on MAVs of various sorts, but also purely animal flight papers have been included. The issue has been edited by two well-known figures in our field, David Lentink and Andy Biewener. The latter is handling most of our mansucripts submitted to JEB. The two editors write an introductory essay, following by the original papers. Have a look here. There will be reason to return to these papers.

Operation snow storm: lab meeting

During the lab meeting today (29 November 2010) the AFL-members that made it to the Ecology Building, in spite of the snow-storm, discussed the recent paper about “The effect of body size on the wing movements of pteropodid bats, with insights into thrust and lift production”. This paper, from the Brown University Group, reports on kinematic parameters studied in six species of bats. The paper concludes that “the ways that bats modulate their wing kinematics to produce thrust and lift over the course of a wing beat cycle are independent of body size”. How convenient if this proves to be true! The authors however thinks that small bats, such as Phyllostomids, may differ from the medium to large sized bats studied here. One reason put forward could be that small bats, using a leading edge vortex, are more insect-like in their use of aerodynamic mechanism, and therefore different from other bats. It will be interesting to find out of smaller species of bats differ in flight.

A new paper on bat flight has now been published by the Brown University group in the Journal of Experimental Biology (Hubel et al. 2010), where they report on the wake dynamics in a medium sized bat, Cynopterus brachyotis, when it is flying at intermediate speeds (5 and 6.7 m/s). The wake is very similar to that found for other bat species studied in Lund, which lend support for the notion of the generality of these results. Hence, it is very nice to see results of bat aerodynamics being confirmed by anther lab. Since papers of bat flight are still quite rare, this paper will be the focus of our next lab meeting, which will be Monday 11 October, 2010.