Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

The science behind swimming

15.09.2014

From whales to larvae, study finds common principles at work in swimming

At nearly 100 feet long and weighing as much as 170 tons, the blue whale is the largest creature on the planet, and by far the heaviest living thing ever seen on Earth. So there's no way it could have anything in common with the tiniest fish larvae, which measure millimeters in length and tip the scales at a fraction of a gram, right?

Not so fast, says L. Mahadevan, the Lola England de Valpine Professor of Applied Mathematics, of Organismic and Evolutionary Biology, and of Physics.

Using simple hydrodynamics, a team of researchers led by Mahadevan was able to show that a handful of principles govern how virtually every animal -- from the tiniest fish to birds to gigantic whales propel themselves though the water. The study is described in a September 14 paper in Nature Physics.

"What we wanted to investigate was how the speed of an organism changes as a function of how large it is, how quickly it moves and how much it moves," Mahadevan said. "To resolve that in detail, however, is very complex, because there is a great deal of differences in morphology and what parts of the body different creatures use to swim. The question is: Is there anything in common across all these organisms? The answer, we found, is yes."

In an effort to uncover those common principles, Mahadevan working with a postdoctoral fellow in his group , Mattia Gazzola, and a colleague Mederic Argentina from the University of Nice, began by trying to unpack the physics of how different creatures swim.

"The traditional approach to swimming phenomena is to take a certain specimen and accurately characterize it via experiments and/or simulations, and try to generalize from there, but it is very hard to strip out specific biological effects from general principles," Gazzola said. "We instead thought that while swimmers exhibit a huge diversity in shapes and kinematics, at the end of the day they all live in the same media, water.

"Therefore we thought that if a unifying mechanistic principle existed, it had to lie in the constraints that the flow environment poses to all its inhabitants," he continued. "And this is a purely physical problem, much easier to solve since it is not affected by biological vagaries. What I like about this paper is that in one line of algebra we derived a compact formula that accounts for 50 years of experiments. This is an example of how powerful minimal modeling can be."

"The basic relationship we wanted to understand was how the input variables – namely the size of the organism, the amount an organism moves and how quickly it moves – control the output variable, which is effectively the speed at which it moves," Mahadevan explained. "What we found is that there is a specific relationship, which can be described by in terms of a simple scaling law with two limits."

The first, which corresponds to creatures moving at intermediate speeds, describes situations where the bulk of the resistance is caused by skin friction, because water "sticks" to the organism's body. At faster speeds, Mahadevan said, the resistance organisms face largely comes from pressure that builds up in front of and around them, which is described by the second limit.

"While it wasn't a surprise that the resistance changed at organisms moved faster, the fact that those challenges could be so simply described was interesting and provocative, because we are talking about organisms that range in size from a few millimeters to the size of a blue whale," Mahadevan said.

Armed with those observations, Mahadevan and colleagues turned to a host of empirical observations that had been made over the past 50-plus years. When those data were plotted on a graph, the researchers found that the swimming speed of virtually every organism, from fish larvae to frogs to birds, amphibians and even whales, could be described by one of the two equations.

The same also held true, Mahadevan said, when Gazzola created complex computer models to solve the governing equations of fluid dynamics to describe how different organisms swim.

"What is particularly interesting is that all the organisms essentially reach the hydrodynamic limits of performance," he said. "Our simple theory, which doesn't distinguish in any detailed way between something like a blue whale and fish larvae, except in the parameters of how large you are, much you move and how quickly you move, can describe all this diversity. That suggests there are general principles at work here."

Peter Reuell | Eurek Alert!
Further information:
http://www.harvard.edu/

Further reports about: Harvard Physics creatures larvae limits observations organism solve swimming

More articles from Life Sciences:

nachricht Nesting aids make agricultural fields attractive for bees
20.07.2017 | Julius-Maximilians-Universität Würzburg

nachricht The Kitchen Sponge – Breeding Ground for Germs
20.07.2017 | Hochschule Furtwangen

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: Manipulating Electron Spins Without Loss of Information

Physicists have developed a new technique that uses electrical voltages to control the electron spin on a chip. The newly-developed method provides protection from spin decay, meaning that the contained information can be maintained and transmitted over comparatively large distances, as has been demonstrated by a team from the University of Basel’s Department of Physics and the Swiss Nanoscience Institute. The results have been published in Physical Review X.

For several years, researchers have been trying to use the spin of an electron to store and transmit information. The spin of each electron is always coupled...

Im Focus: The proton precisely weighted

What is the mass of a proton? Scientists from Germany and Japan successfully did an important step towards the most exact knowledge of this fundamental constant. By means of precision measurements on a single proton, they could improve the precision by a factor of three and also correct the existing value.

To determine the mass of a single proton still more accurate – a group of physicists led by Klaus Blaum and Sven Sturm of the Max Planck Institute for Nuclear...

Im Focus: On the way to a biological alternative

A bacterial enzyme enables reactions that open up alternatives to key industrial chemical processes

The research team of Prof. Dr. Oliver Einsle at the University of Freiburg's Institute of Biochemistry has long been exploring the functioning of nitrogenase....

Im Focus: The 1 trillion tonne iceberg

Larsen C Ice Shelf rift finally breaks through

A one trillion tonne iceberg - one of the biggest ever recorded -- has calved away from the Larsen C Ice Shelf in Antarctica, after a rift in the ice,...

Im Focus: Laser-cooled ions contribute to better understanding of friction

Physics supports biology: Researchers from PTB have developed a model system to investigate friction phenomena with atomic precision

Friction: what you want from car brakes, otherwise rather a nuisance. In any case, it is useful to know as precisely as possible how friction phenomena arise –...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

»We are bringing Additive Manufacturing to SMEs«

19.07.2017 | Event News

The technology with a feel for feelings

12.07.2017 | Event News

Leipzig HTP-Forum discusses "hydrothermal processes" as a key technology for a biobased economy

12.07.2017 | Event News

 
Latest News

Researchers create new technique for manipulating polarization of terahertz radiation

20.07.2017 | Information Technology

High-tech sensing illuminates concrete stress testing

20.07.2017 | Materials Sciences

First direct observation and measurement of ultra-fast moving vortices in superconductors

20.07.2017 | Physics and Astronomy

VideoLinks
B2B-VideoLinks
More VideoLinks >>>