September 2, 2014

Deconstructing the Hummingbird’s Hover

Tiffany Trader

Ever wonder how a hummingbird is able to hover in mid-air, appearing for a moment to defy the laws of gravity? You’re not alone. Vanderbilt University mechanical engineer Haoxiang Luo accessed the XSEDE’s Lonestar supercomputer to run 3D simulations of a hummingbird flight in an attempt to deconstruct its mysterious powers.

Science Writer Jorge Salazar details Luo’s research in a recent article on the TACC website. The science has real-world applications too – for the development of micro and unmanned aerial vehicles.

Luo carried out computer simulations of the three-dimensional flow patterns created by the pumping of the hummingbird’s wings using the Lonestar supercomputer of the Texas Advanced Computing Center.

“We used TACC’s Lonestar for both its CPU time and data storage,” said Luo. “The excellent computing power allowed us to complete the simulations in a reasonable amount of time.”

It was known that the vertical force from the wings is equal to the bird’s body weight, but there still was a lot more to uncover.

The research team used a high-speed camera, which captured 1,000 frames per second, to record the flight of a trained female ruby-throated hummingbird. Non-toxic paint was applied in small dots to the leading and trailing edge of its wings, allowing a MATLAB program to track the dots through space and time.

“The instantaneous force characteristics were previously unknown,” Luo reported. “So was the three-dimensional flow stirred up by the bird. We are the first group to be able to directly quantify the time-varying forces within a stroke cycle.”

The experiment shows that there is relationship between wing motion, the force produced by that motion, and the power consumed in beating their wings, explains Salazar.

Despite the bird’s diminutive stature, this was an exceedingly compute-intensive endeavor, hence the need for a leadership-class supercomputer.

“For a hummingbird with only a 10 centimeter wingspan, the unsteady aerodynamics is complex enough to require millions of mesh points to resolve the many, many small vortices stirred up by the wings — the bird essentially is flying in an ‘ocean of vortices.’ Therefore, efficient algorithms and high-performance computing are necessary for this work,” said Luo.

Luo and his colleagues are planning to expand their study of the hummingbird to see how it performs other aerial maneuvers. The mechanical engineers hope to apply their gleanings to man-made air-crafts, while biologists are interested in the way that the flying ability has evolved over time and in different animal species.

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