Soon, tiny flying robots inspired by insects

Washington – Researchers have discovered some of the underlying physics that could help explain how insects could so quickly recover from a stall in midflight – unlike an aircraft, where a stalled state most often leads to a crash landing.

The analysis, in which the researchers studied the flow around a rotating model wing, improves the understanding of how insects fly and informs the design of small flying robots built for intelligence gathering, surveillance, search-and-rescue, and other purposes.

An insect like a fruit fly hovers in the air by flapping its wings – a complex motion akin 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.

To simulate the basics of this action, Matthew Bross and colleagues at Lehigh University in Bethlehem, PA, studied how water flows around a rotating model wing consisting of a rectangular piece of acrylic that is twice as long as it is wide.

The rotation axis is off to the side of the wing and parallel to its width, so that it rotates 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.

The researchers made detailed three-dimensional computer visualizations of the flow around the wing, finding that a leading-edge vortex – a feature crucial for providing lift – almost immediately appears once the wing starts to rotate after a stalled state.

The study has been published in the journal Physics of Fluids.