Better designs for planes, cars as turbulence puzzle cracked

Air travellers have come to recognise as routine the gut-wrenching sensation they experience as their flight jostles after hitting an 'air-pocket'-scientifically known as turbulence.

Indian researcher Manikandan Mathur is part of a group of Massachusetts Institute of Technology that claims to have found out the mystery behind a phenomenon that often causes among other things unexpected jolts in flights making aircraft to bounce and dip in mid-air.

This they say could ultimately help engineers design better planes, cars, submarines and engines and also reduce oceanic pollution. The results of the research will be published in an upcoming issue of the Physical Review Letters, according to news from MIT.

So what exactly is turbulence? Delhi-based Professor of Physics Dwarkanath Mulherkar explains, "It is anything that produces a quick and abrupt change."

"In turbulent flow the air is continuously changing due to changes in speed and direction. You could say that it is like when a stream of water flows over shoals of rocks or practically any phenomena involving fluid flow such as air and gas mixing in an engine or air whipping across a vehicle's surface," he says.

In daily life the swirls of smoke puffed out from a cigarette, or the swathes of cream poured into coffee or ocean waves breaking on a cliff all count as turbulence.

Auto design guru Dilip Chabbaria says the research may lead to cars being designed faster, cleaner and more efficient.

"Turbulence basically means drag. Though this breakthrough if we can get around that then it definitely pushes designing (automobiles) up two or three stages higher. Definitely we can see faster cars on the roads."

He adds that though the research "seems mumbo jumbo to him, at a macro level it will help aerodynamic engineers in the long run come up with better designs."

The research findings could also perhaps help to reduce pollution in the oceans. "Sediments usually settle down at the floor of the ocean. Whatever pollution is present in the wter bodies goes down to the bed and is covered with soil. But whenever there is turbulence it creates brings up the sediments and makes the water turgid and muddy," says Jai Uppal, Delhi-based environmentalist.

"It is upto some researchers to find out practical applications for the research for use in controlling oceanic pollution," says Uppal.

For quite a long time turbulence has been an 'Achilles heel' for mathematicians and physicians.

The MIT group used water jets to force water from below into a rotating tank of fluid. They seeded the resulting complicated flow with luminescent buoyant particles. When illuminated with a laser, the minuscule polystyrene spheres were visible as they raced around the vortexes and jets.

"With this approach we isolated the very source of turbulent mixing, not just its effect on dye or smoke as earlier studies did," says engineering graduate student Manikandan Mathur who carried out technical analysis in the research.

Imagine that the particles visible in turbulent water are like an army of ants being chased through a bowl of mixed-up red and blue spaghetti.

"The ants love red spaghetti and want to stay close to it but they hate blue spaghetti and won't touch it. And they have to keep running in the bowl under these constraints, stuck in an endless maze forever," says George Haller, professor of mechanical engineering at MIT.