Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Bats in Flight Reveal Unexpected Aerodynamics

23.01.2007
Brown University engineers and biologists have joined forces to record the fine details of wing and body movement in bat flight – together with the patterns of air movement that generate lift. Similar measurements have been made in insects and some birds, but this is the first such data for bats, which are highly flexible and maneuverable flyers and a potential model for engineered micro air vehicles.

The maneuverability of a bat in flight makes even Harry Potter’s quidditch performance look downright clumsy. While many people may be content to simply watch these aerial acrobats in wonder, Kenneth Breuer and Sharon Swartz are determined to understand the detailed aerodynamics of bat flight – and ultimately the evolutionary path that created it.

They have taken a major step toward that goal by combining high-resolution, three-dimensional video recordings with precise measurements of the wake field generated by the bats’ wing movements. Their study, published in the journal Bioinspiration and Biomimetics, marks the first such measurements made in bats and highlights ways in which bat flight appears to differ from bird and insect flight. The results suggest the possibility that a novel lift-generating mechanism may be at work in bats and point to the highly maneuverable mammals as a model for tiny flying machines.

Breuer, a professor of engineering at Brown University, who studied mechanical aerodynamics earlier in his career, is particularly intrigued by bats because “they can generate different wing shapes and motions that other creatures can’t.”

... more about:
»generate »measurements »movement »stroke

“Bats have unique capabilities,” says Breuer, “but the goal is not to build something that looks like a bat. We want to understand bat flight and be able to incorporate some of the features of bat flight into an engineered vehicle.”

Swartz, an associate professor in ecology and evolutionary biology at Brown University, and longtime collaborator with Breuer, is particularly interested in how bats evolved their capabilities. “The assumption has always been that bats evolved from some sort of flying squirrel-type animals,” says Swartz. “Gliding has evolved in mammals seven times. That tells us that it’s really easy for an animal with skin to evolve into a glider, but going from a square gliding wing to a long, skinny flapping wing has not happened seven times. It might have happened once. And now it doesn’t look like bats have any relationship to these gliding things.”

Bat wings are highly articulated, with more than two dozen independent joints and a thin flexible membrane covering them. The videos, shot from four angles simultaneously and then synchronized, show how the complex movements of each wing stroke relate to overall flight speed, body position and angle of attack. Reflective markers placed on joints, along bones and at key points on the wing membrane allowed the researchers to accurately track the position and shape of bones throughout the wing stroke.

Birds and insects can fold and rotate their wings during flight, but bats have many more options. Their flexible skin can catch the air and generate lift or reduce drag in many different ways. During straightforward flight, the wing is mostly extended for the down stroke, but the wing surface curves much more than a bird’s does – giving bats greater lift for less energy. During the up stroke, the bats fold the wings much closer to their bodies than other flying animals, potentially reducing the drag they experience. The wing’s extraordinary flexibility also allows the animals to make 180-degree turns in a distance of less than half a wingspan.

The video images are impressive, but to truly understand how bats fly, the researchers needed to make the invisible visible. The research team filled the test corridor with a fine mist of non-toxic aerosol particles to trace the airflow. As each bat flies down the corridor, she (all the test subjects were female) triggers a laser imaging device, which captures the position, speed and direction of the particles in her wake.

By combining the information from dozens of flights, the research team was able to build a picture of the location and strength of the wake structure at each point in the bat’s wing stroke. The detail of this first reconstruction is limited by the rate at which the laser setup can collect data, but it is clear that the aerodynamics of the bat’s up stroke are quite different than what is seen in birds and insects. During the down stroke, the vortex – which generates much of the lift in flapping-wing flight – closely tracks the animal’s wingtip. In the up stroke, the vortex seems to be shed from another location entirely – perhaps the animal’s wrist joint.

This unusual pattern most likely results from the tremendous flexibility and articulation of the bat’s wing, but it also seems to contribute to a substantial savings in the energy the animal expends. With the receipt of a new laser imaging system that will allow them to capture data at 40 times the rate they can now, the researchers look forward to a much more detailed understanding of this mechanism in the near future. They will also use the new system to examine aerobatic maneuvers such as take off, turning and landing, as well as straight flight.

Swartz and Breuer’s collaboration demonstrates the great promise as well as the great challenge of cross-disciplinary cooperation. “Engineers like to control things and make many, many measurements,” says Swartz, the biologist. “With a living bat, we might spend days getting them to fly through our test area a few times.” Both investigators remark that it took them months to find a common language and set of expectations, but both also cite the other’s insight as being among the most rewarding elements of the project.

The Air Force Office of Scientific Research (AFOSR) supported the work.

Editors: For downloadable video, contact Marty Downs at (401) 863-2752.

Brown University has a fiber link television studio available for domestic and international live and taped interviews and maintains an ISDN line for radio interviews. For more information, call the Office of Media Relations at (401) 863-2476.

Martha Downs | EurekAlert!
Further information:
http://www.brown.edu

Further reports about: generate measurements movement stroke

More articles from Life Sciences:

nachricht The secret sulfate code that lets the bad Tau in
16.07.2018 | American Society for Biochemistry and Molecular Biology

nachricht Colorectal cancer risk factors decrypted
16.07.2018 | Max-Planck-Institut für Stoffwechselforschung

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: First evidence on the source of extragalactic particles

For the first time ever, scientists have determined the cosmic origin of highest-energy neutrinos. A research group led by IceCube scientist Elisa Resconi, spokesperson of the Collaborative Research Center SFB1258 at the Technical University of Munich (TUM), provides an important piece of evidence that the particles detected by the IceCube neutrino telescope at the South Pole originate from a galaxy four billion light-years away from Earth.

To rule out other origins with certainty, the team led by neutrino physicist Elisa Resconi from the Technical University of Munich and multi-wavelength...

Im Focus: Magnetic vortices: Two independent magnetic skyrmion phases discovered in a single material

For the first time a team of researchers have discovered two different phases of magnetic skyrmions in a single material. Physicists of the Technical Universities of Munich and Dresden and the University of Cologne can now better study and understand the properties of these magnetic structures, which are important for both basic research and applications.

Whirlpools are an everyday experience in a bath tub: When the water is drained a circular vortex is formed. Typically, such whirls are rather stable. Similar...

Im Focus: Breaking the bond: To take part or not?

Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.

A frequently used reaction in organic chemistry is nucleophilic substitution. It plays, for example, an important role in in the synthesis of new chemical...

Im Focus: New 2D Spectroscopy Methods

Optical spectroscopy allows investigating the energy structure and dynamic properties of complex quantum systems. Researchers from the University of Würzburg present two new approaches of coherent two-dimensional spectroscopy.

"Put an excitation into the system and observe how it evolves." According to physicist Professor Tobias Brixner, this is the credo of optical spectroscopy....

Im Focus: Chemical reactions in the light of ultrashort X-ray pulses from free-electron lasers

Ultra-short, high-intensity X-ray flashes open the door to the foundations of chemical reactions. Free-electron lasers generate these kinds of pulses, but there is a catch: the pulses vary in duration and energy. An international research team has now presented a solution: Using a ring of 16 detectors and a circularly polarized laser beam, they can determine both factors with attosecond accuracy.

Free-electron lasers (FELs) generate extremely short and intense X-ray flashes. Researchers can use these flashes to resolve structures with diameters on the...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

Leading experts in Diabetes, Metabolism and Biomedical Engineering discuss Precision Medicine

13.07.2018 | Event News

Conference on Laser Polishing – LaP: Fine Tuning for Surfaces

12.07.2018 | Event News

11th European Wood-based Panel Symposium 2018: Meeting point for the wood-based materials industry

03.07.2018 | Event News

 
Latest News

Nano-kirigami: 'Paper-cut' provides model for 3D intelligent nanofabrication

16.07.2018 | Physics and Astronomy

New players, standardization and digitalization for more rail freight transport

16.07.2018 | Transportation and Logistics

Researchers discover natural product that could lead to new class of commercial herbicide

16.07.2018 | Agricultural and Forestry Science

VideoLinks
Science & Research
Overview of more VideoLinks >>>