Quote:
Originally Posted by aerohead
NASA's Paul Soderman sent me a paper he did from his research at NASA Ames.He had studied owl flight and I believe the premise of the work was acoustic Stealth,and not necessarily drag reduction.---------------------- At full take-off power,does the sawtooth blend the interface between the turbo-fan's jet stream and the slower surrounding nacelle air?
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Yes. the sawtooth edge improves on the ducted fan, where the fastest inner core is buffered from the ambient air, reducing the shearing effect between layers, which causes the noise. The sawtooth makes for micro-vortices that to some extent cancel each other out, as the upside flow from one micro vortex impinges on the downside flow of the next.
Where could I get a look at the Soderman paper?
The owl, btw, uses his serrated edge feathers more for noise reduction than for most efficient lift. That's why raptors fly faster, though more noisily--they get breakfast by dint of speed and power, vs. being sneaky.