Order from chaos: Australian vortex studies are first proof of 70-year-old theory of turbulence in fluids

phys.org | 2/13/2017 | Staff
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Two Australian studies published this week offer the first proof of a 70-year-old theory of turbulence.

"The studies confirm a seminal theory of the formation of large-scale vortices from turbulence in 2-D fluid flow, where the large vortices emerge from an apparent chaos of smaller vortices," says author Prof Matt Davis, FLEET's lead on the University of Queensland paper.

Fluids - Two-dimensions - Systems - Electrons - Semiconductors

Fluids restricted to flow in two-dimensions can be observed in systems ranging from electrons in semiconductors, to the surface of soap bubbles, to atmospheric phenomena such as cyclones.

"One of the commonly observed features in such 2-D flow is the formation of large-scale swirling motion of the fluid from the initially chaotic swirling motion typical of turbulent flow, such as Jupiter's famous Great Red Spot," says the Monash study's lead author, Shaun Johnstone.

Theory - Nobel - Laureate - Lars - Onsager

There is, however, a simple theory, proposed in 1949 by the Nobel laureate Lars Onsager, to explain the formation of large-scale vortex motion from initially turbulent 2-D flow.

Despite the appeal of Onsager's physical picture of 2-D turbulence, it can only make quantitative predictions for one special type of fluid: a 'superfluid," which flows without any viscosity or drag, and which can only be realised at extremely low temperatures. This had made a testing of Onsager's theory difficult, until now.

Study - Research - Field - Physics - Superfluids

"The study is broadly relevant to the emerging research field of non-equilibrium physics, and more specifically relevant to study of superfluids and superconductors," says author Prof Kris Helmerson, who works with Johnstone in Monash's School of Physics and Astronomy.

The new research is described in two papers out in Science today, with one experimental study led from FLEET's Monash University node, and the other led from an EQUS/FLEET collaboration at the University of Queensland.

People - Concept - Vortex - Twisting - Shape

Most people are familiar with the concept of a vortex: whether the familiar twisting shape of a tornado, or the simple whirlpool...
(Excerpt) Read more at: phys.org
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