29 January 2013

Hummingbird aerodynamics

Todays lab meeting was fully devoted to hummingbird aerodynamics. Firstly, Marta Wolf, who has just returned from a 2-year postdoc in the flight lab at Berkeley University presented her fascinating results from studies of Anna's hummingbird. We learned a lot about how it is to work with hummingbirds, which seems to be easy on one hand but also difficult as birds mass is only about 4.5 g (like a rather lean goldcrest) and they can rapidly loose weight and may have to be released. Marta showed PIV data on the hovering wake, as well as nice illustrations about hummingbird hovering in a box.
Second on todays agenda was the paper from the Altshuler lab about the hovering wake in hummingbirds, which was published i Experiments in Fluids during the last week. The authors claim their data show that the wake consists of bilateral vortex loops, one shed from each wing. In this sense the hummingbird wake show similarities to the typical wake of bats. However, we had some difficulties on seeing what the authors could see in their smoke visualization movies, while we will have reason to return to these data.

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