Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Fluid particles irreversible in some circumstances, physicists report in this week’s Nature

15.12.2005


When a viscous fluid, such as a jar of honey, is stirred and then unstirred, the contents return to their starting points. However, according to research by a team of physicists headed by New York University’s David Pine, the particles of such fluids do not always return to their original locations. The findings are reported in the latest issue of the journal Nature.

It is a well-established consequence of the laws governing fluid motion that when a viscous fluid is stirred and then unstirred, all parts of the liquid return to their starting points. Pine, along with his colleagues at the Haverford College (PA), the California Institute of Technology, and the Israel Institute of Technology in Haifa, examined what happens to the particles of such fluids during this process.

The researchers studied the movement of tiny polymer beads suspended in a viscous fluid trapped between two concentric cylinders. The cylinders were held 2.5 millimeters apart and could rotate relative to each other. Based on their experiments, the researchers observed that for low concentrations of beads stirred a short distance, the mixing can be reversed so that the beads return to their starting positions. However, at higher concentrations, or with more stirring, mixing became irreversible. The appearance of this irreversible behavior is caused by multiple encounters between individual beads, they concluded.



"The irreversibility of these particles may be explained by the extreme sensitivity of their trajectories to imperceptibly small changes of the particle positions," said Pine, director of NYU’s Center for Soft Matter Research. "Such perturbations might arise from almost anything, such as small imperfections in the particles or by small external forces, and are magnified exponentially by the wakes particles sense due to the motion of other particles suspended in the liquid. Physical systems that exhibit such extreme sensitivity to small perturbations are said to be ’chaotic.’ "

Pine also noted that the results "are interesting from a fundamental point of view because they demonstrate experimentally how vanishingly small perturbations of systems governed by deterministic equations can lead to stochastic non-deterministic behavior."

Mixing processes are difficult to scale up from laboratory bench to production plant because the change in their mixing behavior can be unpredictable. For example, poor understanding of particle migration during injection molding of precision ceramic parts limits manufacturing of large complex shapes. Understanding the influence of collisions between suspended particles may shed new light on the problem.

James Devitt | EurekAlert!
Further information:
http://www.nyu.edu

More articles from Physics and Astronomy:

nachricht What happens when we heat the atomic lattice of a magnet all of a sudden?
18.07.2018 | Forschungsverbund Berlin

nachricht Subaru Telescope helps pinpoint origin of ultra-high energy neutrino
16.07.2018 | National Institutes of Natural Sciences

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: 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

Machine-learning predicted a superhard and high-energy-density tungsten nitride

18.07.2018 | Materials Sciences

NYSCF researchers develop novel bioengineering technique for personalized bone grafts

18.07.2018 | Life Sciences

Why might reading make myopic?

18.07.2018 | Health and Medicine

VideoLinks
Science & Research
Overview of more VideoLinks >>>