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17 April 2014 12:48 pm ,
Vol. 344 ,
Officials last week revealed that the U.S. contribution to ITER could cost $3.9 billion by 2034—roughly four times the...
An experimental hepatitis B drug that looked safe in animal trials tragically killed five of 15 patients in 1993. Now,...
Using the two high-quality genomes that exist for Neandertals and Denisovans, researchers find clues to gene activity...
A new report from the Intergovernmental Panel on Climate Change (IPCC) concludes that humanity has done little to slow...
Astronomers have discovered an Earth-sized planet in the habitable zone of a red dwarf—a star cooler than the sun—500...
Three years ago, Jennifer Francis of Rutgers University proposed that a warming Arctic was altering the behavior of the...
- 17 April 2014 12:48 pm , Vol. 344 , #6181
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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.