Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Vortex loops could untie knotty physics problems

04.03.2013
University of Chicago physicists have succeeding in creating a vortex knot—a feat akin to tying a smoke ring into a knot. Linked and knotted vortex loops have existed in theory for more than a century, but creating them in the laboratory had previously eluded scientists.

Vortex knots should, in principle, be persistent, stable phenomena. "The unexpected thing is that they're not," said Dustin Kleckner, a postdoctoral scientist at UChicago's James Franck Institute. "They seem to break up in a particular way. They stretch themselves, which is a weird behavior."


A vortex loop begins to form a knot during a demonstration in the laboratory of William Irvine, professor in physics at the University of Chicago.

Credit: Robert Kozloff/University of Chicago

This behavior culminates in what the UChicago researchers call "reconnection events." In these events, the loops elongate, begin to circulate in opposite directions, move toward each other and collide (the reconnection). Parts of the vortices then annihilate other parts, changing their configuration from linked or knotted into one that is unlinked or unknotted.

Kleckner and William Irvine, assistant professor in physics, report their findings on the creation and dynamics of vortex rings in Nature Physics, published online Sunday, March 3. Their work relates to deep questions in a variety of physics subfields, including turbulence, plasma physics, ordinary fluids and the more exotic superfluids. Knotted structures are thought to occur in all these phenomena but are difficult or impossible to observe.

"We look at plasma physics and turbulence every day in the sun," Irvine said, yet such phenomena pose longstanding, unsolved scientific puzzles. But knots may offer a means of untangling the complicated behavior of the electrically charged gas in plasma flows, for example, and for understanding the energy transport of complex flows in regular fluids and superfluids.

Conservation of quantities like energy and momentum are among the most important principles in physics. In many systems, the degree of "knottedness" can be represented as a precise physical quantity that also is conjectured to be conserved. "If confirmed, this would deepen our understanding of the dynamics and connections between many disparate physical fields," Irvine said. "We don't know if its true or not, but I think we can finally test this in experiment. There's actually around 50 years of theory on this subject with no clean experiments."

Colliding smoke rings

Irvine became interested in knot physics as a postdoctoral scientist at New York University after watching a smoke-ring demonstration in Washington Square Park. He wondered if he could get colliding smoke rings to become tangled. After unsuccessfully trying to make them himself he learned that others had tried before and failed.

"At some point the enthusiasm wanes and you worry about whether there's a very good reason why nobody has ever done this," Irvine said. "But sometimes going into a new field with a little naivete can be helpful."

Seeing a video of dolphins blowing air-core vortex rings convinced Irvine of the feasibility of the feat. He tried again, with Kleckner's assistance, soon upon arrival at Chicago. "Before we built the lab we had this little prep room, and we started with a little water tank," Irvine said. They tried to generate rings that would collide and then connect with each other, but the effort "failed catastrophically," Irvine said.

The duo overcame their experimental difficulties by designing and fabricating various hydrofoils (wings used in water) on a 3-D printer. They tried approximately 30 different shapes before they successfully created the desired vortices. When accelerated in a water tank at more than 100 g, hydrofoils leave behind bubble-traced vortex loops, whose dynamics the researchers recorded with a high-speed camera.

"The bubbles are a great trick because they allow you to see the core of the vortex very clearly," Irvine said.

The collaborative intellectual spirit and shared resources of the James Franck Institute also proved critical. "We wouldn't have succeeded without this sort of atmosphere," he said.

Lord Kelvin's knots

The roots of Irvine's work date back to the days of Lord Kelvin, more than a century ago. Kelvin had seen a demonstration of a vortex ring by physicist Peter Tait, and was fascinated by their elegance and stability.

"This was at the time when nobody knew what atoms were and the aether was still in fashion," Irvine said. In Kelvin's day, physicists theorized that the universe was filled with a substance known as aether, which transmitted light waves across the vacuum of space much like air transmits sound through the atmosphere. Kelvin thus proposed that atoms were vortex rings and knots in the aether, where the different types of knots formed the building blocks for the periodic table of elements.

The idea that atoms were simply knots tied in the aether eventually failed. But it failed in such an interesting way, Irvine said, that it gave birth to the fruitful study of knotted systems in mathematics and physics.

In future research, Irvine and Kleckner hope to perform some of their experiments at larger scale to investigate whether size would lend greater stability to vortex rings. They also are investigating the fine scale features of the vortices and whether "knottedness" is, or can be, conserved in fine-scale twisting of the vortex loops. "This is not something we presently know," Kleckner said.

Steve Koppes | EurekAlert!
Further information:
http://www.uchicago.edu

More articles from Physics and Astronomy:

nachricht Nanostructures taste the rainbow
29.06.2017 | California Institute of Technology

nachricht X-ray photoelectron spectroscopy under real ambient pressure conditions
28.06.2017 | 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: Making Waves

Computer scientists use wave packet theory to develop realistic, detailed water wave simulations in real time. Their results will be presented at this year’s SIGGRAPH conference.

Think about the last time you were at a lake, river, or the ocean. Remember the ripples of the water, the waves crashing against the rocks, the wake following...

Im Focus: Can we see monkeys from space? Emerging technologies to map biodiversity

An international team of scientists has proposed a new multi-disciplinary approach in which an array of new technologies will allow us to map biodiversity and the risks that wildlife is facing at the scale of whole landscapes. The findings are published in Nature Ecology and Evolution. This international research is led by the Kunming Institute of Zoology from China, University of East Anglia, University of Leicester and the Leibniz Institute for Zoo and Wildlife Research.

Using a combination of satellite and ground data, the team proposes that it is now possible to map biodiversity with an accuracy that has not been previously...

Im Focus: Climate satellite: Tracking methane with robust laser technology

Heatwaves in the Arctic, longer periods of vegetation in Europe, severe floods in West Africa – starting in 2021, scientists want to explore the emissions of the greenhouse gas methane with the German-French satellite MERLIN. This is made possible by a new robust laser system of the Fraunhofer Institute for Laser Technology ILT in Aachen, which achieves unprecedented measurement accuracy.

Methane is primarily the result of the decomposition of organic matter. The gas has a 25 times greater warming potential than carbon dioxide, but is not as...

Im Focus: How protons move through a fuel cell

Hydrogen is regarded as the energy source of the future: It is produced with solar power and can be used to generate heat and electricity in fuel cells. Empa researchers have now succeeded in decoding the movement of hydrogen ions in crystals – a key step towards more efficient energy conversion in the hydrogen industry of tomorrow.

As charge carriers, electrons and ions play the leading role in electrochemical energy storage devices and converters such as batteries and fuel cells. Proton...

Im Focus: A unique data centre for cosmological simulations

Scientists from the Excellence Cluster Universe at the Ludwig-Maximilians-Universität Munich have establised "Cosmowebportal", a unique data centre for cosmological simulations located at the Leibniz Supercomputing Centre (LRZ) of the Bavarian Academy of Sciences. The complete results of a series of large hydrodynamical cosmological simulations are available, with data volumes typically exceeding several hundred terabytes. Scientists worldwide can interactively explore these complex simulations via a web interface and directly access the results.

With current telescopes, scientists can observe our Universe’s galaxies and galaxy clusters and their distribution along an invisible cosmic web. From the...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Plants are networkers

19.06.2017 | Event News

Digital Survival Training for Executives

13.06.2017 | Event News

Global Learning Council Summit 2017

13.06.2017 | Event News

 
Latest News

Nanostructures taste the rainbow

29.06.2017 | Physics and Astronomy

New technique unveils 'matrix' inside tissues and tumors

29.06.2017 | Life Sciences

Cystic fibrosis alters the structure of mucus in airways

29.06.2017 | Health and Medicine

VideoLinks
B2B-VideoLinks
More VideoLinks >>>