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the nation's airports are busier than

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ever with thousands of planes taking off

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and landing daily passengers and people

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living around airports are often

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reminded that air transport is not

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always the quietest mode of

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transportation nasa continues working

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with partners in industry and academia

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to help alleviate the problem of noisy

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flow protruding in

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aeronautics researcher james bridges of

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nasa's glenn research center in

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cleveland discusses chevron engine

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nozzle technology

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a nasa innovation to help airplanes fly

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quieter very good at reducing noise the

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chevrons are the sawtooth pattern that

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you can see me if i hold at this angle a

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little bit better you can see the

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sawtooth pattern that's what is called

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the chevron

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and that is a change from just a regular

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smooth round lip that most nozzles have

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that change modifies how the flow

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downstream of the engine makes noise

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makes it so that it doesn't make as much

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noise which is obviously what we will

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want the aircraft to be quieter these

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are being used in the aircraft that are

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being turned off the production line

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today are the ones that will soon be

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coming out production lines they've been

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in in the initial flight test the

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development of chevrons is the one a

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good example of the kind of work it

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requires in this country and

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to bring ideas from fundamental research

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all the way to a product there was

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people working in academia with nasa

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sponsorship for 20 30 years people doing

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a lot of work it very it's sometimes

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hard to recognize that this is going to

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ever turn into something really useful

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but it's it's in a scientific pursuit

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and then when you pull a lot of

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different ideas together but with

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engineers who have problems to solve

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then you start making progress on on the

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real problems right now we have several

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aeronautics programs that are working on

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reducing noise as part of our whole

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green aviation initiative some of them

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are worried about propulsion noise the

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noise that the fan makes and some of

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them are worried about the airframe

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noise the noise of the landing gear and

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flaps and slats and everything else

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makes that make the aircraft so noisy on

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approach there's a lot of fundamental

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science that still needs to be done to

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understand that to understand ways to

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reduce that so things like the serrated

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edges these chevrons on these nozzles

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here when applied to helicopter blades

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can potentially also be a reduction for

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helicopter blade noise and that is the

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that is at a very fundamental level

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understanding how that all works is what

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nasa is all about

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this nozzle we have some tabs which hang

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out some which are neutral some which

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protrude in

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and here we had a

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one lobe which was

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outwards compared to the way the norm a

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normal nozzle would look and then some

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which then protruded inwards we have all

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the all of these chevrons are the same

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amount of in and out they have just a

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the chevron which gives you the

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variation in the edge

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problem is that the air coming out the

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back of the engine makes a lot of noise

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as the turbulent

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produces

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these changes to the nozzle

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change the noi change the turbulence of

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the flow it comes out the back of the