Flying like a bat
Bats in the laboratory
While the experiment has already been successfully carried out with large birds such as geese, it is very difficult to teach a bat to fly in a wind tunnel. Rectilinear flight and the discipline of a squadron, are not part of this flying mammal’s locomotive register. That’s not a problem, thought the researchers at ULg. Let’s put a model of a bat in a wind tunnel instead, an artefact that resembles the animal as closely as possible. It was the researchers in Manchester who carried out this part of the work, a sophisticated model mainly composed of latex to reproduce the wing membranes and a metallic structure for the skeleton. The model was a Plecotus auritus (brown long-eared bat), characterised by its large ears. “It’s a static model”, stresses Greg Dimitriadis. “The wings are deployed but they don’t flap. It’s as though we are studying the bat gliding.” Placed in ULg’s wind tunnel, the model was subjected to forces which were recorded by aerodynamic load sensors. The wind tunnel’s airspeed can reach 60 metres per second (216 kph), but it is limited to 10 m/s (36 kph), which corresponds to this bat’s maximum flight speed. An initial series of measurements related specifically to the role of the animal’s long ears. “It’s obvious they play an aerodynamic role”, explains G. Dimitriadis. “But what is it? Our study showed that in a horizontal position, the ears give the animal lift. They complement the role of the wings. In a vertical position, they serve as a brake. And in a differential position, i.e. with one ear raised and the other horizontal, they allow the bat to turn even more quickly.” These results were published in 2008 in the specialised review Acta Chiropterologica.
Gardiner James D, Dimitriadis Grigorios, Codd Jonathan R & al, A potential role for bat tail membranes in flight control, in PLoS ONE (2011), 6(3), 18214