Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

“Gray’s Paradox” Solved: Researchers Discover Secret of Speedy Dolphins

26.11.2008
For decades the puzzle has prompted much attention, speculation, and conjecture in the scientific community. But now, armed with cutting-edge flow measurement technology, researchers at Rensselaer Polytechnic Institute have tackled the problem and conclusively solved Gray’s Paradox.

There was something peculiar about dolphins that stumped prolific British zoologist Sir James Gray in 1936.

He had observed the sea mammals swimming at a swift rate of more than 20 miles per hour, but his studies had concluded that the muscles of dolphins simply weren’t strong enough to support those kinds of speeds. The conundrum came to be known as “Gray’s Paradox.”

For decades the puzzle prompted much attention, speculation, and conjecture in the scientific community. But now, armed with cutting-edge flow measurement technology, researchers at Rensselaer Polytechnic Institute have tackled the problem and conclusively solved Gray’s Paradox.

“Sir Gray was certainly on to something, and it took nearly 75 years for technology to bring us to the point where we could get at the heart of his paradox,” said Timothy Wei, professor and acting dean of Rensselaer’s School of Engineering, who led the project. “But now, for the first time, I think we can safely say the puzzle is solved. The short answer is that dolphins are simply much stronger than Gray or many other people ever imagined.”

Wei is presenting his findings today at the 61st Annual Meeting of the American Physical Society (APS) Division of Fluid Dynamics in San Antonio, Texas. Collaborators on the research include Frank Fish, a biologist at West Chester University in Pennsylvania; Terrie Williams, a marine biologist at the University of California, Santa Cruz; Rensselaer undergraduate student Yae Eun Moon; and Rensselaer graduate student Erica Sherman.

After studying dolphins, Gray said in 1936 that they are not capable of producing enough thrust, or power-induced acceleration, to overcome the drag created as the mammal sped forward through the water. This drag should prevent dolphins from attaining significant speed, but simple observation proved otherwise – a paradox. In the absence of a sound explanation, Gray theorized that dolphin skin must have special drag-reducing properties.

More than 70 years later, Wei has developed a tool that conclusively measures the force a dolphin generates with its tail.

Wei created this new state-of-the-art water flow diagnostic technology by modifying and combining force measurement tools developed for aerospace research with a video-based flow measurement technique known as Digital Particle Image Velocimetry, which can capture up to 1,000 video frames per second.

Wei videotaped two bottlenose dolphins, Primo and Puka, as they swam through a section of water populated with hundreds of thousands of tiny air bubbles. He then used sophisticated computer software to track the movement of the bubbles. The color-coded results show the speed and in what direction the water is flowing around and behind the dolphin, which allowed researchers to calculate precisely how much force the dolphin was producing.

See a DPIV video of Primo here: http://www.rpi.edu/news/video/wei/dolphin.html

Wei also used this technique to film dolphins as they were doing tail-stands, a trick where the dolphins “walk” on water by holding most of their bodies vertical above the water while supporting themselves with short, powerful thrusts of their tails.

The results show that dolphins produce on average about 200 pounds of force when flapping their tail – about 10 times more force than Gray originally hypothesized.

“It turns out that the answer to Gray’s Paradox had nothing to do with the dolphins’ skin,” Wei said. “Dolphins can certainly produce enough force to overcome drag. The scientific community has known this for a while, but this is the first time anyone has been able to actually quantitatively measure the force and say, for certain, the paradox is solved.”

At peak performance, the dolphins produced between 300 and 400 pounds of force. Human Olympic swimmers, by comparison, peak at about 60 to 70 pounds of force, Wei said. He knows this for a fact because he has been working with U.S.A. Swimming over the past few years to use these same bubble-tracking DPIV and force-measuring techniques to better understand how elite swimmers interact with the water, and improve lap times.

“It was actually a natural extension to go from swimmers to dolphins,” said Wei, whose research ranges from aeronautical and hydrodynamic flow of vehicles to more biological topics dealing with the flow of cells and fluid in the human body.

The dolphins Wei filmed, Primo and Puka, are retired U.S. Navy dolphins who now live at the Long Marine Laboratory at UC Santa Cruz.

Wei said the research team will likely continue to investigate the flow dynamics and force generation of other marine animals, which could yield new insight into how different species have evolved as a result of their swimming proficiency.

“Maybe sea otters,” he said.

For more information on Wei’s work with Olympic swimmers, visit: http://news.rpi.edu/update.do?artcenterkey=2477

Michael Mullaney | Newswise Science News
Further information:
http://news.rpi.edu/update.do?artcenterkey=2477
http://www.rpi.edu

More articles from Physics and Astronomy:

nachricht Climate cycles may explain how running water carved Mars' surface features
02.12.2016 | Penn State

nachricht What do Netflix, Google and planetary systems have in common?
02.12.2016 | University of Toronto

All articles from Physics and Astronomy >>>

The most recent press releases about innovation >>>

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

Im Focus: Novel silicon etching technique crafts 3-D gradient refractive index micro-optics

A multi-institutional research collaboration has created a novel approach for fabricating three-dimensional micro-optics through the shape-defined formation of porous silicon (PSi), with broad impacts in integrated optoelectronics, imaging, and photovoltaics.

Working with colleagues at Stanford and The Dow Chemical Company, researchers at the University of Illinois at Urbana-Champaign fabricated 3-D birefringent...

Im Focus: Quantum Particles Form Droplets

In experiments with magnetic atoms conducted at extremely low temperatures, scientists have demonstrated a unique phase of matter: The atoms form a new type of quantum liquid or quantum droplet state. These so called quantum droplets may preserve their form in absence of external confinement because of quantum effects. The joint team of experimental physicists from Innsbruck and theoretical physicists from Hannover report on their findings in the journal Physical Review X.

“Our Quantum droplets are in the gas phase but they still drop like a rock,” explains experimental physicist Francesca Ferlaino when talking about the...

Im Focus: MADMAX: Max Planck Institute for Physics takes up axion research

The Max Planck Institute for Physics (MPP) is opening up a new research field. A workshop from November 21 - 22, 2016 will mark the start of activities for an innovative axion experiment. Axions are still only purely hypothetical particles. Their detection could solve two fundamental problems in particle physics: What dark matter consists of and why it has not yet been possible to directly observe a CP violation for the strong interaction.

The “MADMAX” project is the MPP’s commitment to axion research. Axions are so far only a theoretical prediction and are difficult to detect: on the one hand,...

Im Focus: Molecules change shape when wet

Broadband rotational spectroscopy unravels structural reshaping of isolated molecules in the gas phase to accommodate water

In two recent publications in the Journal of Chemical Physics and in the Journal of Physical Chemistry Letters, researchers around Melanie Schnell from the Max...

Im Focus: Fraunhofer ISE Develops Highly Compact, High Frequency DC/DC Converter for Aviation

The efficiency of power electronic systems is not solely dependent on electrical efficiency but also on weight, for example, in mobile systems. When the weight of relevant components and devices in airplanes, for instance, is reduced, fuel savings can be achieved and correspondingly greenhouse gas emissions decreased. New materials and components based on gallium nitride (GaN) can help to reduce weight and increase the efficiency. With these new materials, power electronic switches can be operated at higher switching frequency, resulting in higher power density and lower material costs.

Researchers at the Fraunhofer Institute for Solar Energy Systems ISE together with partners have investigated how these materials can be used to make power...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

ICTM Conference 2017: Production technology for turbomachine manufacturing of the future

16.11.2016 | Event News

Innovation Day Laser Technology – Laser Additive Manufacturing

01.11.2016 | Event News

#IC2S2: When Social Science meets Computer Science - GESIS will host the IC2S2 conference 2017

14.10.2016 | Event News

 
Latest News

UTSA study describes new minimally invasive device to treat cancer and other illnesses

02.12.2016 | Medical Engineering

Plasma-zapping process could yield trans fat-free soybean oil product

02.12.2016 | Agricultural and Forestry Science

What do Netflix, Google and planetary systems have in common?

02.12.2016 | Physics and Astronomy

VideoLinks
B2B-VideoLinks
More VideoLinks >>>