Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Turbulence Restrains Itself

08.11.2002


Like rapidly flowing gases and liquids, magnetically confined plasmas in tokamaks and related fusion devices exhibit a high degree of turbulence, which can generally destroy the optimal conditions for producing fusion energy. In a deeply encouraging new result, scientists have experimentally confirmed that turbulence can actually limit its own ability to wreak havoc.


Theoretical picture of self-generated turbulence flows in a tokamak cross section


Computer simulations of turbulence in the DIII-D tokamak agree with recent DIII-D experiments. Color contours illustrate the highly elongated structure of turbulence in the electron density



Researchers at the DIII-D tokamak at General Atomics have discovered that turbulence generates its own flows that act as a self-regulating mechanism. These flows, which are predicted theoretically and have been observed in computer simulations, create a "shearing" or tearing action that destroys turbulent eddies, as indicated by the figure. Such flows are like the large-scale zonal jets and patterns seen in the atmospheres of Jupiter and other large planets.

These turbulent flows have been clearly observed in recent experiments at DIII-D by using a special imaging system. The imaging measurements are obtained at a rate of one million frames per second and have a spatial resolution of about 1 cm. Observing and identifying these unique turbulence flows experimentally, and comparing their characteristics with theory, is helping to advance researchers’ understanding of this complex and crucial phenomena taking place in high temperature fusion plasmas.


The roiling turbulence inside tokamaks represents some of the most complex physics on the planet. Using the full power of the world’s largest supercomputers, scientists in separate work have now been able to fully simulate the movement of tokamak particles and heat due to turbulence. Implementing new algorithms to incorporate very complex physics, they included the effects of super-fast electrons and the recent practice of rotating the plasma, like horses in a merry go round, for higher-pressure tokamak operation and higher-energy output. Making it possible to directly compare DIII-D turbulence experiments with numerical calculations for the first time, these simulations may also help greatly in making reliable predictions for larger tokamaks and future commercial-scale fusion reactors.

Contacts
D-III experiments:
A collaboration between the University of Wisconsin-Madison, and the DIII-D National Fusion Facility at General Atomics.
George R. McKee, (858) 455-2419, mckee@fusion.gat.com
Raymond J. Fonck, University of Wisconsin-Madison, General Atomics

Supercomputer simulations:
Jeff Candy, General Atomics, (858) 455-2593, jeff.candy@gat.com

David Harris | EurekAlert!
Further information:
http://www.aps.org/meet/DPP02/baps/press/press6.html
http://www.aps.org/

More articles from Physics and Astronomy:

nachricht NIST researchers boost microwave signal stability a hundredfold
26.05.2020 | National Institute of Standards and Technology (NIST)

nachricht ATLAS telescope discovers first-of-its-kind asteroid
25.05.2020 | University of Hawaii at Manoa

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: New double-contrast technique picks up small tumors on MRI

Early detection of tumors is extremely important in treating cancer. A new technique developed by researchers at the University of California, Davis offers a significant advance in using magnetic resonance imaging to pick out even very small tumors from normal tissue. The work is published May 25 in the journal Nature Nanotechnology.

researchers at the University of California, Davis offers a significant advance in using magnetic resonance imaging to pick out even very small tumors from...

Im Focus: I-call - When microimplants communicate with each other / Innovation driver digitization - "Smart Health“

Microelectronics as a key technology enables numerous innovations in the field of intelligent medical technology. The Fraunhofer Institute for Biomedical Engineering IBMT coordinates the BMBF cooperative project "I-call" realizing the first electronic system for ultrasound-based, safe and interference-resistant data transmission between implants in the human body.

When microelectronic systems are used for medical applications, they have to meet high requirements in terms of biocompatibility, reliability, energy...

Im Focus: When predictions of theoretical chemists become reality

Thomas Heine, Professor of Theoretical Chemistry at TU Dresden, together with his team, first predicted a topological 2D polymer in 2019. Only one year later, an international team led by Italian researchers was able to synthesize these materials and experimentally prove their topological properties. For the renowned journal Nature Materials, this was the occasion to invite Thomas Heine to a News and Views article, which was published this week. Under the title "Making 2D Topological Polymers a reality" Prof. Heine describes how his theory became a reality.

Ultrathin materials are extremely interesting as building blocks for next generation nano electronic devices, as it is much easier to make circuits and other...

Im Focus: Rolling into the deep

Scientists took a leukocyte as the blueprint and developed a microrobot that has the size, shape and moving capabilities of a white blood cell. Simulating a blood vessel in a laboratory setting, they succeeded in magnetically navigating the ball-shaped microroller through this dynamic and dense environment. The drug-delivery vehicle withstood the simulated blood flow, pushing the developments in targeted drug delivery a step further: inside the body, there is no better access route to all tissues and organs than the circulatory system. A robot that could actually travel through this finely woven web would revolutionize the minimally-invasive treatment of illnesses.

A team of scientists from the Max Planck Institute for Intelligent Systems (MPI-IS) in Stuttgart invented a tiny microrobot that resembles a white blood cell...

Im Focus: NASA's Curiosity rover finds clues to chilly ancient Mars buried in rocks

By studying the chemical elements on Mars today -- including carbon and oxygen -- scientists can work backwards to piece together the history of a planet that once had the conditions necessary to support life.

Weaving this story, element by element, from roughly 140 million miles (225 million kilometers) away is a painstaking process. But scientists aren't the type...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

Dresden Nexus Conference 2020: Same Time, Virtual Format, Registration Opened

19.05.2020 | Event News

Aachen Machine Tool Colloquium AWK'21 will take place on June 10 and 11, 2021

07.04.2020 | Event News

International Coral Reef Symposium in Bremen Postponed by a Year

06.04.2020 | Event News

 
Latest News

NIST researchers boost microwave signal stability a hundredfold

26.05.2020 | Physics and Astronomy

Complex genetic regulation of flowering time

26.05.2020 | Life Sciences

'One-way' electronic devices enter the mainstream

26.05.2020 | Information Technology

VideoLinks
Science & Research
Overview of more VideoLinks >>>