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Considered an icon of conservation science, researchers at World Wildlife Fund (WWF) headquarters in Washington, D.C.,...
The new atlas, which shows the distribution of important trace metals and other substances, is the first product of...
Early in April, the first of a fleet of environmental monitoring satellites will lift off from Europe's spaceport in...
Since 2000, U.S. government health research agencies have spent almost $1 billion on an effort to churn out thousands...
Magdalena Koziol, a former postdoc at Yale University, was the victim of scientific sabotage. Now, she is suing the...
Antiretroviral drugs can protect people from becoming infected by HIV. But so-called pre-exposure prophylaxis, or PrEP...
Two studies show that eating a diet low in protein and high in carbohydrates is linked to a longer, healthier life, and...
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Electromagnetic Waves May Cut Turbulence
22 May 2000 5:00 pm
Turbulence is expensive. By some estimates, overcoming the swirling drag that slows down submarines, boats, and airplanes costs billions of dollars a year. Now researchers have proposed a method that might one day harness electromagnetic fields to smooth the flow of salt water.
As water streams past a submarine's hull, the flow splits into many pairs of current called streaks. Each streak consists of a fast and a slow ribbon of water. Eddies circulate between the halves of each streak. These eddies grow rapidly until they burst, vibrating the hull and slowing the submarine.
But there may be a way to cut drag force by almost 30%, according to computer simulations of turbulent ocean-water flows reported in the 19 May issue of Science by mechanical engineer Yiqing Du of the Massachusetts Institute of Technology and applied mathematician George Karniadakis of Brown University. They modeled the ways in which electromagnetic pulses might break up the turbulence in the electrically conductive salt water passing over a hull. The researchers found in simulations and lab tests that the pulses prevent streaks from forming along the hull, so the explosive eddies never appear. "We cut the legs off the turbulence," Karniadakis says.
The technique could be a tremendous advance in fluid dynamics, if the simulations are borne out by upcoming experiments, says Richard Philips of the Naval Undersea Warfare Center in Newport, Rhode Island.