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 Astronomers find unexpected, dust-obscured star formation in distant galaxy
24.03.2017 | University of Massachusetts at Amherst

nachricht Gravitational wave kicks monster black hole out of galactic core
24.03.2017 | NASA/Goddard Space Flight Center

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: Giant Magnetic Fields in the Universe

Astronomers from Bonn and Tautenburg in Thuringia (Germany) used the 100-m radio telescope at Effelsberg to observe several galaxy clusters. At the edges of these large accumulations of dark matter, stellar systems (galaxies), hot gas, and charged particles, they found magnetic fields that are exceptionally ordered over distances of many million light years. This makes them the most extended magnetic fields in the universe known so far.

The results will be published on March 22 in the journal „Astronomy & Astrophysics“.

Galaxy clusters are the largest gravitationally bound structures in the universe. With a typical extent of about 10 million light years, i.e. 100 times the...

Im Focus: Tracing down linear ubiquitination

Researchers at the Goethe University Frankfurt, together with partners from the University of Tübingen in Germany and Queen Mary University as well as Francis Crick Institute from London (UK) have developed a novel technology to decipher the secret ubiquitin code.

Ubiquitin is a small protein that can be linked to other cellular proteins, thereby controlling and modulating their functions. The attachment occurs in many...

Im Focus: Perovskite edges can be tuned for optoelectronic performance

Layered 2D material improves efficiency for solar cells and LEDs

In the eternal search for next generation high-efficiency solar cells and LEDs, scientists at Los Alamos National Laboratory and their partners are creating...

Im Focus: Polymer-coated silicon nanosheets as alternative to graphene: A perfect team for nanoelectronics

Silicon nanosheets are thin, two-dimensional layers with exceptional optoelectronic properties very similar to those of graphene. Albeit, the nanosheets are less stable. Now researchers at the Technical University of Munich (TUM) have, for the first time ever, produced a composite material combining silicon nanosheets and a polymer that is both UV-resistant and easy to process. This brings the scientists a significant step closer to industrial applications like flexible displays and photosensors.

Silicon nanosheets are thin, two-dimensional layers with exceptional optoelectronic properties very similar to those of graphene. Albeit, the nanosheets are...

Im Focus: Researchers Imitate Molecular Crowding in Cells

Enzymes behave differently in a test tube compared with the molecular scrum of a living cell. Chemists from the University of Basel have now been able to simulate these confined natural conditions in artificial vesicles for the first time. As reported in the academic journal Small, the results are offering better insight into the development of nanoreactors and artificial organelles.

Enzymes behave differently in a test tube compared with the molecular scrum of a living cell. Chemists from the University of Basel have now been able to...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

International Land Use Symposium ILUS 2017: Call for Abstracts and Registration open

20.03.2017 | Event News

CONNECT 2017: International congress on connective tissue

14.03.2017 | Event News

ICTM Conference: Turbine Construction between Big Data and Additive Manufacturing

07.03.2017 | Event News

 
Latest News

Electrical 'switch' in brain's capillary network monitors activity and controls blood flow

27.03.2017 | Health and Medicine

Clock stars: Astrocytes keep time for brain, behavior

27.03.2017 | Life Sciences

Sun's impact on climate change quantified for first time

27.03.2017 | Earth Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>