AUSTIN, Texas--The convoluted tangle describing turbulence has been visualized for the first time by a group of researchers from The University of Texas at Austin and the Massachusetts Institute of Technology (MIT).
Their work, published in the April 6 issue of Physical Review Letters, may ultimately help engineers design more efficient planes, cars, submarines and engines.
Turbulence is important in almost all phenomena involving fluid flow, such as air and gas mixing in an engine and air whipping across the surface of a vehicle. However, a comprehensive description of turbulent fluid motion remains one of the major unsolved problems in physics.
The research revealed an underlying skeleton of turbulence, which is a complex tangle of curves corresponding to two very different motions of particles in the flow.
The first type of curve attracts fluid particles, while the second type of curve repels fluid particles. These two sets of curves repeatedly cross one another, forming a dense evolving tangle that is the skeleton of turbulence.
Laboratory experiments were designed and conducted by doctoral student Jori Ruppert-Felsot and his adviser, Physics Professor Harry Swinney, in The University of Texas at Austin’s Center for Nonlinear Dynamics.
They produced turbulence by rapidly pumping water into and out of a rotating two-foot high cylindrical tank. The influence of the rotation was comparable to the effect of the Earth’s rotation on atmospheric and oceanic turbulence.
“The experiment was designed to achieve a better understanding of the kind of turbulence that occurs in the atmosphere and oceans, where the Earth’s rotation strongly affects the flow and leads to structures such as hurricanes and atmospheric high- and low- pressure systems,” said Swinney.
The researchers determined the speed of the flows by using laser imaging techniques to track tiny particles seeded in the fluid.
The technical analysis of the flow velocity was carried out by MIT mechanical engineering graduate student Manikandan Mathur. Mathur’s work is jointly supervised by MIT co-authors Dr. George Haller, professor of mechanical engineering, and Dr. Thomas Peacock, assistant professor of mechanical engineering.Using mathematical tools, Mathur uncovered a convoluted tangle embedded in the flow.
This research was supported by the Office of Naval Research, the National Science Foundation and the Air Force Office for Scientific Research.
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