The holidays are here and the nation's airports are busier than ever –thousands of airplanes taking off and landing. Passengers and people living around airports are reminded that the airplane is not the quietest mode of transportation; certainly not as quiet as a sleigh pulled by eight tiny reindeer. Fear not, because even while travelers are heading home, NASA continues working with others in industry and academia on technologies that will create a more silent night (and day) around airports.
One of the most recent noise-reducing technologies shepherded through the research process by NASA and now making a difference on commercial jet engines is chevrons.
Chevrons are the sawtooth pattern seen on the trailing edges of some jet engine nozzles. As hot air from the engine core mixes with cooler air blowing through the engine fan, the shaped edges serve to smooth the mixing, which reduces turbulence that creates noise. "Successes like chevrons are the result of a lot of different, hard-working people and are the result of a lot of very small efforts that all come together, often across many scientific disciplines," said James Bridges, the associate principal investigator responsible for coordinating aircraft noise research at NASA.
The new Boeing 787 is among the most modern jets relying on chevrons to reduce engine noise levels. It sports chevrons on the nacelles, or fan housings. The Boeing 747-8 has chevrons on both the nacelles and inner core engine nozzles.
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