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Old 07-06-2015, 05:13 PM   #8 (permalink)
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trailing edge

Automotive drag is associated with separation-induced pressure drag.
If you have a streamlined shape,the trailing edges will also be streamlined and the car will only suffer from surface friction drag which cannot be removed.
Any 'feather down' attached to the aft-body would already be embedded within the thickened turbulent boundary layer and only add turbulence and drag.
As to noise,most of that is coming from the tires.
Owls fly at very low flight velocity,below critical Reynolds number.They're in a laminar boundary layer up to maximum cross-section and 1st minimum pressure on the wings.It's nothing like an automobile.
Their down is attached to nerve endings.As their angle of attack approaches stall,their central nervous system will cause the bird to morph it's wings such to defeat the stall,within a closed-loop feedback system.Again,it's nothing like an automobile.
Owl technology was very important during the Vietnam War,where the USA had aircraft operating overhead at very low altitude which could not be heard from the ground.A large suite of features combined to allow the acoustic stealth performance.NASA has studied Raptor/Owl acoustics extensively.
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