Subscribe free to our newsletters via your
. Earth Science News .

Which has a more efficient 'engine': A tuna or a whale?
by Staff Writers
Chicago IL (SPX) May 14, 2014

File image.

A large gray whale and a much smaller skipjack tuna each propels itself through water. Which is the more efficient swimmer? It has been difficult to compare propulsion efficiencies of animals of different sizes, like comparing apples and oranges, but now Northwestern University researchers have developed a new metric, or standard, to measure individual energy consumption efficiency and make such a comparison possible.

Contrary to what one might expect, the Northwestern researchers found that, despite the great difference in mass, the whale and the tuna are almost equally efficient.

Much like a semi-trailer truck needs more fuel to go the same distance compared to a small car, one might think the much heavier whale would consume more energy compared to the tuna. While this is true, does it mean that the muscular "engine" propelling the whale is less efficient compared to the tuna or is the higher fuel consumption of the whale an unavoidable consequence of the laws of physics?

The whale's higher fuel consumption is unavoidable, the researchers report, and the engine efficiencies of the whale and tuna are similar. The new Northwestern metric for efficiency that enabled this comparison could be extremely useful in designing underwater vehicles -- such as those used to study fragile coral reefs, repair damaged deep-sea oil rigs or investigate sunken ships -- to be as efficient and agile as a real fish.

"Our study is about how energy flow changes with size or mass," said Neelesh Patankar, who led the research.

"This is good insight to have in the transportation field, whether you are working with cars, ships or planes. What are the limits of how good you can become? Our metric can be used to determine the point where an animal or a vehicle would function most efficiently. We want to know the sweet spot."

Patankar is a professor of mechanical engineering in Northwestern's McCormick School of Engineering and Applied Science. He currently is doing a mini-sabbatical at Argonne National Laboratory's Advanced Vehicle Technology Center investigating efficiency metrics for automotive vehicles.

The metric, called the energy consumption coefficient, is a non-dimensional measure of fuel consumption. Now, for the first time, scientists and engineers can compare apples to apples, no matter what the size of the animals or vehicles, to understand the energy efficiency of a self-propelled body or machine. This metric is as useful to quantify efficiency of self-propelled bodies as the drag coefficient metric is to quantify aerodynamic shapes of vehicles.

While the Northwestern study focused on swimming and flying animals, the concept potentially could be applied to define efficiencies of cars, too -- something the researchers are now pursuing.

"The study helps quench my curiosity about how nature works, but, as an engineer, I also want to see utility," Patankar said. "The energy consumption coefficient can be an important tool in designing self-propelled underwater vehicles as well as aerial vehicles. And, as a driver, I also would like to know how efficient my car is, information currently not available to me."

The study will be published the week of May 12 by the Proceedings of the National Academy of Sciences (PNAS).

The energy consumption coefficient takes into consideration metabolic rate, muscle mass and, of course, physics. After developing the metric, first author Rahul Bale and Patankar applied it to data for energy consumption by animals available from biologists.

The data represented thousands of species of swimming and flying animals. Swimming animals ranged from tiny larval zebrafish to massive mammalian swimmers such as dolphins and whales. Flying animals ranged from tiny insects to the largest flying birds.

The new metric successfully collapsed energy consumption data on to a single trend with respect to mass -- mass that varied almost a trillion times from the smallest to the largest animal. The key idea was not to plot the energy consumption itself versus mass but instead to plot energy consumption normalized by an appropriate scale that accounts for the size of the animal.

This is conceptually analogous to how aerodynamic shapes of vehicles are assessed not by comparing drag but by comparing drag that is suitably normalized -- the normalized drag being the drag coefficient.

The new metric, the researchers said, is a step in the direction of eventually providing efficiency information to consumers about their cars.

The title of the paper is "Energy efficiency and allometry of movement of swimming and flying animals." In addition to Patankar and Bale, other authors of the paper are Max Hao and Amneet Pal Singh Bhalla, both from Northwestern.


Related Links
Northwestern University
Follow the Whaling Debate

Comment on this article via your Facebook, Yahoo, AOL, Hotmail login.

Share this article via these popular social media networks DiggDigg RedditReddit GoogleGoogle

Memory Foam Mattress Review
Newsletters :: SpaceDaily :: SpaceWar :: TerraDaily :: Energy Daily
XML Feeds :: Space News :: Earth News :: War News :: Solar Energy News

Japan imports tonnes of whale meat from Iceland: Greenpeace
Tokyo (AFP) May 09, 2014
Environmentalists on Friday lashed out after Japan imported 2,000 tonnes of frozen whale meat from Iceland, in what they say is continued defiance of world opinion over the hunting of the mammals. Packages containing meat from fin whales were unloaded Thursday from a vessel that had travelled from Iceland to Osaka, western Japan, said Junichi Sato of Greenpeace Japan. The ship left Icela ... read more

Australia commits up to $84 million to MH370 search

Tech troubles hinder resumption of MH370 search

Hollywood revives Godzilla, Japan's 'king of monsters'

Italy warns EU on asylum as shipwreck survivors land

Ultrafast laser technique developed to observe electron action

Quantum trimer -- from a distance

Conducting polymer films decorated with biomolecules for cell research use

The Tallest Skyscrapers Currently Under Construction

The physics of ocean undertow

MH370 search on hold after trouble with mini-sub

Imploding sub a 'tragic loss': Titanic director

Eight dead, hundreds ill from 'tainted water' in Philippines

West Antarctic Glacier Loss Appears Unstoppable

A Slow Collapse As West Antarctic Melts

Greenland melting due equally to global warming, natural variations

International team maps nearly 200,000 global glaciers in quest for sea rise answers

Corn dwarfed by temperature dip suitable for growing in caves, mines

Winners and losers in cereal production from El Nino

Bee biodiversity boosts crop yields

Study says pesticides to blame for honeybee colony collapse

Questions remain as China remembers 6 years since quake

Water extraction boosts California quake risk: study

Three dead in China rain storms: government

Yellowstone Geyser Eruptions Mostly Influenced By Internal Processes

Meni Mbugha brings pygmy style to city life in DR Congo

Troops needed to shore up shaky South Sudan peace: US

US general in Nigeria to aid search for schoolgirls

No US troops to aid search for Nigeria schoolgirls: Hagel

US military opens door to gender treatment for Manning

Preschool teacher depression linked to behavioral problems in children

Longevity gene may boost brain power

Rocks lining Peruvian desert pointed to ancient fairgrounds

The content herein, unless otherwise known to be public domain, are Copyright 1995-2014 - Space Media Network. All websites are published in Australia and are solely subject to Australian law and governed by Fair Use principals for news reporting and research purposes. AFP, UPI and IANS news wire stories are copyright Agence France-Presse, United Press International and Indo-Asia News Service. ESA news reports are copyright European Space Agency. All NASA sourced material is public domain. Additional copyrights may apply in whole or part to other bona fide parties. Advertising does not imply endorsement, agreement or approval of any opinions, statements or information provided by Space Media Network on any Web page published or hosted by Space Media Network. Privacy Statement All images and articles appearing on Space Media Network have been edited or digitally altered in some way. Any requests to remove copyright material will be acted upon in a timely and appropriate manner. Any attempt to extort money from Space Media Network will be ignored and reported to Australian Law Enforcement Agencies as a potential case of financial fraud involving the use of a telephonic carriage device or postal service.