Researchers at Virginia Tech in US are studying how bats are able to fly by flapping their wings and will apply that knowledge toward designing small flying vehicles known as "micro air vehicles".
More than 1,000 species of bats have hand membrane wings, meaning that their fingers are essentially "webbed" and connected by a flexible membrane.
But understanding how bats use their wings to manipulate the air around them is extremely challenging - primarily because both experimental measurements on live creatures and the related computer analysis are quite complex.
"Bats have different wing shapes and sizes, depending on their evolutionary function. Typically, bats are very agile and can change their flight path very quickly - showing high maneuverability for midflight prey capture, so it's of interest to know how they do this," said Danesh Tafti, the William S Cross professor in the Department of Mechanical Engineering and director of the High Performance Computational Fluid Thermal Science and Engineering Lab at Virginia Tech.
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"It distorts its wing shape and size continuously during flapping," Tafti noted.
For example, it increases the area of the wing by about 30 per cent to maximise favourable forces during the downward movement of the wing, and it decreases the area by a similar amount on the way up to minimise unfavourable forces.
The force coefficients generated by the wing are "about two to three times greater than a static airfoil wing used for large airplanes," said Kamal Viswanath, co-author of the study.
"We'd also like to explore other bat wing motions, such as a bat in level flight or a bat trying to maneuver quickly to answer questions, including: What are the differences in wing motion and how do they translate to air movement and forces that the bat generates? And finally, how can we use this knowledge to control the flight of an autonomous flying vehicle?" Tafti added.
The findings are published in the journal Physics of Fluids.