The Secrets of Insect Flight Revealed in New Study

Insects are dexterous creatures in the air, quickly changing directions as they hover, stall, dive and weave. Now, scientists have identified some of the underlying physics of insect flight, explaining how they can recover so quickly from a stall midflight, unlike conventional fixed wing aircraft.

When an airplane stalls, it takes a few moments for it to recover. Not given enough time, though, the aircraft can crash land. Insects, in contrast, recover almost immediately. In order to find out why that is, the researchers studied the flow of air around a rotating wing model. This allowed them to improve the understanding of how insects fly and may inform the design of small flying robots built for intelligence gathering, surveillance and search-and-rescue.

An insect, such as a fruit fly, can hover in the air by flapping its wings--a complex motion that's similar to the freestyle stroke in swimming. The wing rotates in a single plane, and by varying the angle between the plane and its body, the insect can fly forward from a hovering position.

Actually simulating the basics of this relatively complex action, though, wasn't easy. The scientists studied how water flows around a rotating model wing consisting of a rectangular piece of acrylic that was twice as long as it was wide. The rotation axis was off to the side of the wing and parallel to its width so that it rotated like half of an airplane propeller. To simulate forward motion, a scenario in which the insect is accelerating or climbing, the researchers pumped water in the direction perpendicular to the plane of rotation.

"We were able to identify the development of flow structure over an insect-scaled wing over a range of forward flight velocities," said Matthew Bross, one of the researchers, in a news release.

The scientists also made detailed three-dimensional computer visualizations of the flow around the wing. This allowed them to see that a leading edge vortex, which is a feature that's crucial for providing lift, almost immediately appears once the wing starts to rotate after a stalled state. This finding in particular explains exactly how insects manage to recover so quickly within flight.

The findings are published in the journal Physics of Fluids.