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 New quantum liquid crystals may play role in future of computers
21.04.2017 | California Institute of Technology

nachricht Light rays from a supernova bent by the curvature of space-time around a galaxy
21.04.2017 | Stockholm University

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: Deep inside Galaxy M87

The nearby, giant radio galaxy M87 hosts a supermassive black hole (BH) and is well-known for its bright jet dominating the spectrum over ten orders of magnitude in frequency. Due to its proximity, jet prominence, and the large black hole mass, M87 is the best laboratory for investigating the formation, acceleration, and collimation of relativistic jets. A research team led by Silke Britzen from the Max Planck Institute for Radio Astronomy in Bonn, Germany, has found strong indication for turbulent processes connecting the accretion disk and the jet of that galaxy providing insights into the longstanding problem of the origin of astrophysical jets.

Supermassive black holes form some of the most enigmatic phenomena in astrophysics. Their enormous energy output is supposed to be generated by the...

Im Focus: A Quantum Low Pass for Photons

Physicists in Garching observe novel quantum effect that limits the number of emitted photons.

The probability to find a certain number of photons inside a laser pulse usually corresponds to a classical distribution of independent events, the so-called...

Im Focus: Microprocessors based on a layer of just three atoms

Microprocessors based on atomically thin materials hold the promise of the evolution of traditional processors as well as new applications in the field of flexible electronics. Now, a TU Wien research team led by Thomas Müller has made a breakthrough in this field as part of an ongoing research project.

Two-dimensional materials, or 2D materials for short, are extremely versatile, although – or often more precisely because – they are made up of just one or a...

Im Focus: Quantum-physical Model System

Computer-assisted methods aid Heidelberg physicists in reproducing experiment with ultracold atoms

Two researchers at Heidelberg University have developed a model system that enables a better understanding of the processes in a quantum-physical experiment...

Im Focus: Glacier bacteria’s contribution to carbon cycling

Glaciers might seem rather inhospitable environments. However, they are home to a diverse and vibrant microbial community. It’s becoming increasingly clear that they play a bigger role in the carbon cycle than previously thought.

A new study, now published in the journal Nature Geoscience, shows how microbial communities in melting glaciers contribute to the Earth’s carbon cycle, a...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Expert meeting “Health Business Connect” will connect international medical technology companies

20.04.2017 | Event News

Wenn der Computer das Gehirn austrickst

18.04.2017 | Event News

7th International Conference on Crystalline Silicon Photovoltaics in Freiburg on April 3-5, 2017

03.04.2017 | Event News

 
Latest News

Fraunhofer HHI with latest VR technologies at NAB in Las Vegas

24.04.2017 | Trade Fair News

New quantum liquid crystals may play role in future of computers

21.04.2017 | Physics and Astronomy

A promising target for kidney fibrosis

21.04.2017 | Health and Medicine

VideoLinks
B2B-VideoLinks
More VideoLinks >>>