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!
--
"President Trump's behavior is becoming more alarming
and illogical. In 55 years of service in the
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have never encountered this level of anger, insulting
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-Barry R McCaffrey, Gen (ret) U.S.Army
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