Winged insects to inspire nextgen tiny air vehicles

WASHINGTON - Creating tiny air vehicles that mimic the flapping of winged insects is a popular notion, but require a complex combination of pitching and plunging motions to oscillate the flapping wings.

Now, researchers at the Georgia Institute of Technology propose using flexible wings that are driven by a simple sinusoidal flapping motion.

“We found that the simple up and down wavelike stroke of wings at the resonance frequency is easier to implement and generates lift comparable to winged insects that employ a significantly more complex stroke,” said Alexander Alexeev.

Unlike fixed-wing and rotary-wing air vehicles, micro air vehicles integrate lifting, thrusting and hanging into a flapping wing system, and have the ability to cruise a long distance with a small energy supply.

“When you want to create smaller and smaller vehicles, the aerodynamics change a lot and modeling becomes important. We tried to gain insight into the flapping aerodynamics by using computational models and identifying the aerodynamic forces necessary to drive these very small flying machines,” said Alexeev.

Alexeev and Masoud used three-dimensional computer simulations to examine how flexible wings worked. They found that at tilted elastic wings driven by a simple harmonic stroke generated lift comparable to that of small insects that employ a significantly more complex stroke.

In addition, the simulations identified one flapping regime that enabled maximum lift and another that revealed maximum efficiency.

The efficiency was maximized at a flapping frequency 30 percent higher than the frequency for maximized lift.

Now, the researchers plan to examine how flapping wings can be effectively controlled in different flow conditions including unsteady gusty environments. They are also investigating whether wings with non-uniform structural and mechanical properties and wings driven by an asymmetric stroke may further improve the resonance performance of flapping wings.

The study was published in the May issue of the journal Physical Review E. (ANI)