100-year-old problem's solution may enhance fuel efficiency of cars, planes

Washington, September 26 : Researchers at Massachusetts Institute of Technology (MIT) have opened the door for significant improvements in the fuel efficiency of cars and aeroplanes by solving a century old engineering problem regarding how fluids-such as gasses and liquids-move.

The researchers say that their new mathematical and experimental work can help predict where the airflow around a vehicle cannot keep up and will detach from it, a phenomenon scientifically known as aerodynamic separation.

Fluid flows affect everything in our world, from blood flow to geophysical convection, and, thus, engineers constantly seek ways of controlling separation in such flows to reduce losses and increase efficiency.

Thomas Peacock, the Atlantic Richfield Career Development Associate Professor in the Department of Mechanical Engineering, says that controlling fluid flows lies at the heart of a wide range of scientific problems, including improving the performance of vehicles.

In 1904, Ludwig Prandtl derived the exact mathematical conditions for flow separation to occur.

But his work had two major restrictions - it applied only to steady flows like those around a car moving at a constant low speed, and it only applied to idealized two-dimensional flows.

"Most engineering systems, however, are unsteady. Conditions are constantly changing. For example, cars accelerate and decelerate, as do planes during manoeuvres, takeoff and landing. Furthermore, fluids of technological interest really flow in our three-dimensional world," says George Haller, a visiting professor in the Department of Mechanical Engineering.

Consequently, ever since 1904, scientists have been trying to extend Prandtl's results to real-life problems that are based on unsteady three-dimensional flows, Haller adds.

The researcher claims that his group's mathematical work now allows them to extend the theory to three dimensions.

Experiments conducted by Peacock and his colleagues provide strong backing to Haller's work.

"While we fully trust George's new mathematical results, the engineering community is usually sceptical until they also see experimental results," says Peacock.

The researchers, however, concede that it is too early to quantify the level of improvement in performance of cars and planes that might stem from their studies.

They insist that more work must be done before it can be applied to commercial technologies.

"This is the tip of the iceberg, but we've shown that this theory works," Peacock said.

ANI