On Fri, 10 Aug 2018 09:59:27 -0700, Stormin' Norman
<norman@schwarzkopf.in.memorium> wrote:
>On 10 Aug 2018 09:19:59 -0700, Miloch <Miloch_member@newsguy.com>
>wrote:
>
>>In article <mjdrmd90hlnpsrah6f4d49eqnb61i8tn4q@4ax.com>, Old Geezerr says...
>>>
>>>On 10 Aug 2018 06:33:38 -0700, Miloch <Miloch_member@newsguy.com>
>>>wrote:
>>>
>>>>
>>> A frily dilly trim job.
>>>
>>>Dave:
>>>
>>>
>>
>>Looks like they used a giant pair of pinking shears
>>
>>
>
>The chevrons at the rear of the engines are to reduce sound.
>
>Here is the explanation from Boeing"
>
> "To combat the sound of jet-blast from the rear of the engine,
>Boeing, General Electric, and NASA developed serrated edges called
>chevrons for the back of the nacelle and the engine exhaust nozzle.
>The chevrons reduce jet blast noise by controlling the way the air
>mixes after passing through and around the engine.
>
> The acoustic liners and chevrons are such effective noise
>suppressors that several hundred pounds of sound insulation may be
>eliminated from the fuselage."
>
>http://www.boeing.com/news/frontiers/archive/2005/december/ts_sf07.html
>
>
>And here is what NASA has to say:
>
> "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.
>
> ... 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."
>
>https://www.nasa.gov/topics/aeronautics/features/bridges_chevron_events.html
>
>
>I think it is some great engineering!
It is impressive how quiet all the latest Boeings are.
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