Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Randomness Rules in Turbulent Flows

03.06.2011
It seems perfectly natural to expect that two motorists who depart from the same location and follow the same directions will end up at the same destination.

But according to a Johns Hopkins University mathematical physicist, this is not true when the “directions” are provided by a turbulent fluid flow, such as you find in a churning river or stream. Verifying earlier theoretical predictions, Gregory Eyink’s computer experiments reveal that, in principle, two identical small beads dropped into the same turbulent flow at precisely the same starting location will end up at different – and entirely random – destinations.

“This result is as astonishing and unexpected as if I told you that I fired a gun aimed at precisely the same point on a target but the bullet went in a completely different direction each and every time. It’s surprising because, even though the beads are exactly the same and the flow of water is exactly the same, the result is different,” said Eyink, professor of applied mathematics and statistics at the university’s Whiting School of Engineering. “It is crucial here that the flow is turbulent — as in whitewater rapids or a roiling volcanic plume — and not smooth, regular flow as in a quiet-running stream.”

An article about the phenomenon appears in a recent issue of Physical Review E and is available online here http://link.aps.org/doi/10.1103/PhysRevE.83.056405

To conduct his study, Eyink used a virtual “stream” that is part of an online public database of turbulent flow created with Whiting School colleagues Charles Meneveau and Randal Burns, as well as with physicist Alexander Szalay of the Krieger School of Arts and Sciences. Into this “stream” Eyink tossed virtual “particles” at precisely the same point and let them drift within the fluid. The researcher then randomly “kicked” each of the particles as they moved along, with different “kicks” at different points along the way. The particles, as one would expect when subjected to different “kicks,” followed different paths.

“But here’s the surprising thing,” Eyink explained. “As the kicks got weaker and weaker, the particles still followed random – and different – paths. In the end, the computer experiment seemed to show that the particles would follow different paths even if the kicks vanished completely.”

This phenomenon is called “spontaneous stochasticity,” which basically means that objects placed in a turbulent flow – even objects that are identical and which are dropped into the same spot – will end up in different places.

“Thus, we know that ‘God plays dice’ not only with subatomic particles, but also with everyday particles like soot or dust carried by a turbulent fluid,” Eyink said.

Eyink’s study also revealed that the magnetic lines of force that are carried along in a moving magnetized fluid (like a stream of molten metal) move in a completely random way when the fluid flow is turbulent. This contradicts the fundamental principle of “magnetic flux-freezing” formulated by Nobel Prize-winning astrophysicist Hannes Alfvéen in 1942, which states that magnetic lines of force are carried along in a moving fluid like strands of thread cast into a flow.

“This principle of Alfveen’s is fundamental to our understanding of how fluid motions in the Earth’s core and in the sun generate those bodies’ magnetic fields, and my study may provide a solution to the longstanding puzzle of why flux freezing seems to fail in violent solar flares and in other turbulent plasma flows,” Eyink said.

This study was supported by the National Science Foundation.

Eyink’s home page: http://www.ams.jhu.edu/~eyink/

Lisa De Nike | Newswise Science News
Further information:
http://www.jhu.edu

More articles from Physics and Astronomy:

nachricht Engineering team images tiny quasicrystals as they form
18.08.2017 | Cornell University

nachricht Astrophysicists explain the mysterious behavior of cosmic rays
18.08.2017 | Moscow Institute of Physics and Technology

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: Fizzy soda water could be key to clean manufacture of flat wonder material: Graphene

Whether you call it effervescent, fizzy, or sparkling, carbonated water is making a comeback as a beverage. Aside from quenching thirst, researchers at the University of Illinois at Urbana-Champaign have discovered a new use for these "bubbly" concoctions that will have major impact on the manufacturer of the world's thinnest, flattest, and one most useful materials -- graphene.

As graphene's popularity grows as an advanced "wonder" material, the speed and quality at which it can be manufactured will be paramount. With that in mind,...

Im Focus: Exotic quantum states made from light: Physicists create optical “wells” for a super-photon

Physicists at the University of Bonn have managed to create optical hollows and more complex patterns into which the light of a Bose-Einstein condensate flows. The creation of such highly low-loss structures for light is a prerequisite for complex light circuits, such as for quantum information processing for a new generation of computers. The researchers are now presenting their results in the journal Nature Photonics.

Light particles (photons) occur as tiny, indivisible portions. Many thousands of these light portions can be merged to form a single super-photon if they are...

Im Focus: Circular RNA linked to brain function

For the first time, scientists have shown that circular RNA is linked to brain function. When a RNA molecule called Cdr1as was deleted from the genome of mice, the animals had problems filtering out unnecessary information – like patients suffering from neuropsychiatric disorders.

While hundreds of circular RNAs (circRNAs) are abundant in mammalian brains, one big question has remained unanswered: What are they actually good for? In the...

Im Focus: RAVAN CubeSat measures Earth's outgoing energy

An experimental small satellite has successfully collected and delivered data on a key measurement for predicting changes in Earth's climate.

The Radiometer Assessment using Vertically Aligned Nanotubes (RAVAN) CubeSat was launched into low-Earth orbit on Nov. 11, 2016, in order to test new...

Im Focus: Scientists shine new light on the “other high temperature superconductor”

A study led by scientists of the Max Planck Institute for the Structure and Dynamics of Matter (MPSD) at the Center for Free-Electron Laser Science in Hamburg presents evidence of the coexistence of superconductivity and “charge-density-waves” in compounds of the poorly-studied family of bismuthates. This observation opens up new perspectives for a deeper understanding of the phenomenon of high-temperature superconductivity, a topic which is at the core of condensed matter research since more than 30 years. The paper by Nicoletti et al has been published in the PNAS.

Since the beginning of the 20th century, superconductivity had been observed in some metals at temperatures only a few degrees above the absolute zero (minus...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Call for Papers – ICNFT 2018, 5th International Conference on New Forming Technology

16.08.2017 | Event News

Sustainability is the business model of tomorrow

04.08.2017 | Event News

Clash of Realities 2017: Registration now open. International Conference at TH Köln

26.07.2017 | Event News

 
Latest News

A Map of the Cell’s Power Station

18.08.2017 | Life Sciences

Engineering team images tiny quasicrystals as they form

18.08.2017 | Physics and Astronomy

Researchers printed graphene-like materials with inkjet

18.08.2017 | Materials Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>