What we know about aerodynamic theory makes no sense when applied to insects or anything as small as or smaller than a hummingbird. Over the past 15 years, in particular, scientists have been painting a new picture of the unconventional aerodynamic mechanisms of these tiny creatures.
Jeff Dawson, an associate professor in Carleton’s Department of Biology since 2005, undertook his post-doctoral fellowship at Cambridge under the ingenious insect-flight expert Charles Ellington. Ellington analyzed the kinematics and aerodynamics of hovering insects such as bees and moths and his visualization of the airflow around insect wings kicked off the “revolution” in aerodynamics.
“As insect wings move from up stroke to down stroke, they create mini-tornadoes. These spiralling vortices of air greatly increase lift during the down stroke,” explains Dawson.
It’s certainly not how a bird flies or an airplane or, for that matter, the fixed-wing robotic drones that are the talk of the town these days.
Dawson, who has always thought the physiology of insects is “cool stuff,” has investigated a range of insect behaviour, from the interaction of moths and echolocating bats to the “steering” muscles of locusts.
As a neuroethologist, Dawson is interested in how animals avoid predators, what kind of defence mechanisms they use to protect themselves. These mechanisms might involve changing body posture or wing kinematics that shift the balance of aerodynamic forces at play.
Dawson says locusts, with their relatively simple ears and nervous systems, provide an excellent model to study auditory sensorimotor integration mechanisms and aerodynamic mechanisms required for stability and for changing direction quickly.
His Insect Flight Group is delving deeply into the seemingly disparate fields of neuroethology and biomechanics as they examine the flight of the humble locust in a wind tunnel and through high-speed cinematography. Dawson and his students’ research have even taken them back in time to study the aerodynamic characteristics of an extinct proto-pterygote insect, built with the help of a 3-D printer in larger-than-life proportions using a fossil as a foundation.
A 1,500-litre “tow tank” that looks like a gigantic see-through bath tub allows researchers to visualize the movement of insect wings through water (which is comparable to their movement through air) by using lasers and stereo photography.
And his Locust Car Project, a mobile robotics device that allows researchers to study how insects process and use sensory information during flight, received quite a bit of attention after Dawson rebuilt an original prototype he and his software engineering friend Ron Harding had created in 2000. An on-board computer interprets locust muscle activity and generates signals to activate the car’s wheels, so a locust is actually driving and steering the device.
The Insect Flight Group also has a variety of robotic devices it uses for experiments, devices generally built from a panoply of gears, cables, pulleys and electronic components Dawson likes to gather, tinker with and repurpose. His lab, he says, is an example of resourcefulness, low technology, recycling and multidisciplinarity.
While Dawson admits his research is “pure,” he envisions contributing to a technology that could be used in search and rescue operations or inspections of dangerous environments. Imagine, for example, an unmanned aerial vehicle the size of a pill bottle, with tiny camera, microphone and sensors on board.
How close are we to such a tiny flapping-wing robot?
“Not very,” admits Dawson. “It would be expensive to build and hard to control. But imagine, in this multidisciplinary education environment, electronic engineers, mechanical engineers and aerospace engineers working side by side with biologists to study the complexity of how insects fly.
“Maybe, just maybe,” adds Dawson, “my research could make the development of these technologies possible.”