There has always been a need to efficiently carry more people and more cargo. And so the science and engineering of getting large aircraft off the ground is very well understood.
But what about flight at a small scale? Say the scale of a dragonfly, a bird or a bat?
Hui Hu, an Iowa State University associate professor of aerospace engineering, said there hasn’t been a need to understand the airflow, the eddies and the spinning vortices created by flapping wings and so there haven’t been many engineering studies of small-scale flight. But that’s changing.
The U.S. Air Force, for example, is interested in insect-sized nano-air vehicles or bird-sized micro-air vehicles. The vehicles could fly microphones, cameras, sensors, transmitters and even tiny weapons right through a terrorist’s doorway.
So how do you design a little flier that’s fast and agile as a house fly?
Hu says a good place to start is nature itself.
And so for a few years he’s been using wind tunnel tests and imaging technologies to learn why dragonflies and bats are such effective fliers. How, for example, do flapping frequency, flight speed and wing angle affect the lift and thrust of a flapping wing?
Hu’s studies of bio-inspired aerodynamic designs began in 2008 when he spent the summer on a faculty fellowship at the Air Force Research Laboratory at Eglin Air Force Base in Florida. Over the years he’s published papers describing aerodynamic performance of different kinds of flapping wings.
A study based on the dragonfly, for example, found the uneven, sawtooth surface of the insect’s wing performed better than a smooth airfoil in the slow-speed, high-drag conditions of small-scale flight. Using particle image velocimetry – an imaging technique that uses lasers and cameras to measure and record flows – Hu found the corrugated wing created tiny air cushions that kept oncoming airflow attached to the wing’s surface. That stable airflow helped boost performance in the challenging flight conditions. By describing the underlying physics of dragonfly flight, Hu and Jeffery Murphy, a former Iowa State graduate student, won a 2009 Best Paper Award in applied aerodynamics from the American Institute of Aeronautics and Astronautics.
Another study of bat-like wings found the built-in flexibility of membrane-covered wings helped decrease drag and improve flight performance.
And what about building tiny flying machines that use flapping wings? Can engineers come up with a reliable way to make that work?
Hu has been looking into that, too.
He’s using piezoelectrics, materials that bend when subject to an electric current, to create flapping movements. That way flapping depends on feeding current to a material, rather than relying on a motor, gears and other moving parts.
Hu has also used his wind tunnel and imaging tests to study how pairs of flapping wings work together – just like they do on a dragonfly. He learned wings flapping out of sync (one wing up while the second is down) created more thrust. And tandem wings working side by side, rather than top to bottom, maximize thrust and lift.
Hu said these kinds of physics and aerodynamics lessons – and many more – need to be learned before engineers can design effective nano- and micro-scale vehicles.
And so he’s getting students immersed in the studies.
Hu has won a $150,000, three-year National Science Foundation grant that sends up to 12 Iowa State students to China’s Shanghai Jiao Tong University for eight weeks of intensive summer research. The students work at the university’s J.C. Wu Aerodynamics Research Center to study bio-inspired aerodynamics and engineering problems.
“We’re just now learning what makes a dragonfly work,” Hu said. “There was no need to understand flight at these small scales. But now the Defense Advanced Research Projects Agency and the Air Force say there is a need and so there’s an effort to work on it. We’re figuring out many, many interesting things we didn’t know before.”Hui Hu, Aerospace Engineering, 515-294-0094, firstname.lastname@example.org
Mike Krapfl | Newswise
Scientists from Hannover develop a novel lightweight production process
27.09.2017 | IPH - Institut für Integrierte Produktion Hannover gGmbH
PRESTO – Highly Dynamic Powerhouses
15.05.2017 | JULABO GmbH
University of Maryland researchers contribute to historic detection of gravitational waves and light created by event
On August 17, 2017, at 12:41:04 UTC, scientists made the first direct observation of a merger between two neutron stars--the dense, collapsed cores that remain...
Seven new papers describe the first-ever detection of light from a gravitational wave source. The event, caused by two neutron stars colliding and merging together, was dubbed GW170817 because it sent ripples through space-time that reached Earth on 2017 August 17. Around the world, hundreds of excited astronomers mobilized quickly and were able to observe the event using numerous telescopes, providing a wealth of new data.
Previous detections of gravitational waves have all involved the merger of two black holes, a feat that won the 2017 Nobel Prize in Physics earlier this month....
Material defects in end products can quickly result in failures in many areas of industry, and have a massive impact on the safe use of their products. This is why, in the field of quality assurance, intelligent, nondestructive sensor systems play a key role. They allow testing components and parts in a rapid and cost-efficient manner without destroying the actual product or changing its surface. Experts from the Fraunhofer IZFP in Saarbrücken will be presenting two exhibits at the Blechexpo in Stuttgart from 7–10 November 2017 that allow fast, reliable, and automated characterization of materials and detection of defects (Hall 5, Booth 5306).
When quality testing uses time-consuming destructive test methods, it can result in enormous costs due to damaging or destroying the products. And given that...
Using a new cooling technique MPQ scientists succeed at observing collisions in a dense beam of cold and slow dipolar molecules.
How do chemical reactions proceed at extremely low temperatures? The answer requires the investigation of molecular samples that are cold, dense, and slow at...
Scientists from the Max Planck Institute of Quantum Optics, using high precision laser spectroscopy of atomic hydrogen, confirm the surprisingly small value of the proton radius determined from muonic hydrogen.
It was one of the breakthroughs of the year 2010: Laser spectroscopy of muonic hydrogen resulted in a value for the proton charge radius that was significantly...
17.10.2017 | Event News
10.10.2017 | Event News
10.10.2017 | Event News
20.10.2017 | Information Technology
20.10.2017 | Materials Sciences
20.10.2017 | Interdisciplinary Research