Owl Wings Are Helping Silence Airplanes, Fans, And Wind Turbines

[Ecky]

Source

Owls are often considered nature’s stealth fighters, and it turns out their ability to silently is a result of a unique wing structure not found in any other bird. Now that researchers know the owl’s secret, they can make lots of stuff silent—everything from bedroom ceiling fans to massive wind turbines.

What contributes to a noisy wing or fan blade as it slices through the air is the turbulence from its trailing edge. But once a team of researchers from the University of Cambridge, Virginia Tech, Lehigh University, and Florida Atlantic University put an owl’s wing under a microscope, they discovered that its flight feathers had a unique soft downy covering, a flexible array of bristles along its leading edge, and a porous fringe coming off the trailing edge.

Working together, these three unique characteristics smooth out the air as it passes over an owl’s wing while also scattering the sounds produced—like how a stealth fighter scatters radar signals—so that it can catch its prey unawares.

To replicate this structure on a wind turbine, for starters, the researchers first experimented with covering those massive blades with a fine mesh material that was similar to what’s used in wedding veils. It succeeded in reducing the blade’s surface noise by a whopping 30 decibels, but ultimately proved impractical for real-world use.

As an alternative, the researchers created a custom prototype material using 3D printing techniques that reduce noise in wind tunnel tests by as much as 10 decibels, without sacrificing aerodynamics. And as this technique is further tested and refined, it will make those giant blades even quieter.

But in addition to reducing the amount of noise pollution generated by a massive wind farm, the new coating could allow wind turbines to actually run at higher speeds, making them more efficient and increasing their power output. And while applying the material to a plane’s wings is a little more challenging given the speeds they travel at, it has the potential to make an air craft more fuel efficient and also more comfortable and quieter for those riding inside.

What I wonder is if adding a fine mesh coating that reduces trailing-edge drag would add enough skin friction to offset the reduction in turbulence. Either way though, silence is something to be valued.

[AbramWagner]

Interesting how how a lot of designs they look to nature and copy it.

[NickelB NL]

Nature has found its ways already via evolution. Almost all we know now comes from nature. But the details from alot of stuff is getting griped bij people now.

[AbramWagner]

Originally Posted by NickelB NL

Nature has found its ways already via evolution. Almost all we know now comes from nature. But the details from alot of stuff is getting griped bij people now.

I was thinking more along the lines that it points to intelligent design of a creator but every one is entitled to their opinion.

[freebeard]

Small-'C' creator, I see. I lean more toward the Anthropic Principle, Weak or Strong.

This is a good example of Biomimetics, and a different approach to semi-permeable surfaces generally.

...the researchers first experimented with covering those massive blades with a fine mesh material that was similar to what’s used in wedding veils.

The reporter covers the Society page? A furry trip strip on the leading edge and a serrated trailing edge would be more analogous.

Edit: Then there is this from The Register:

Engineers 3D-print ROBOT SEAHORSE, then BATTER it with rubber mallets

It being El Reg, you'll notice the title in the actual URL is "/seahorse_tails_robot_tales_were_all_going_to_die/".

[RunningStrong]

I'm sceptical that there'll be any perceivable decrease in airplace noise (both interior and exterior) but the Wind Turbines is certainly an interesting application and a turbine noise is often used by anti-wind turbine groups.

Originally Posted by AbramWagner

Interesting how how a lot of designs they look to nature and copy it.

Similar to how wing tips have been adopted only fairly recently.

It's a funny thing, we've known for years that animals are capable of some amazing things that we would do well to replicate, but the technology and funding to really look into it has only recently become available in some instances.

[freebeard]

Originally Posted by RunningStrong

I'm sceptical[sic]...

Latest practice with turbojets is a serrated trailing edge. It must be quantifiable.



The real fun is when you take what Bucky Fuller called 'generalizable principles' from nature and apply them to things nature never addressed. Beetle wings to LCD screens kind of stuff. Or Bucky-tubes/balls and graphene.

[aerohead]

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.

[freebeard]

A large suite of features combined to allow the acoustic stealth performance.NASA has studied Raptor/Owl acoustics extensively.

IIRC it was a light plane with a five-bladed prop and a large (like the whole tail of the fuselage) muffler.

Now we have Black Helicopters.

[Otto]

Google for Lockheed YO-3 aircraft, essentially a Sweitzer sailplane with 5 or 6 bladed slow moving propeller, engine, and a long muffler. It was a dog to fly, being under powered and over weight, but never took a round of enemy fire, since it pretty much flew at night and Charlie never heard it coming. There is an alumni website for YO-3 guys.

The FBI had a couple of these Army surplus planes at Pt. Mugu in the late '70s. Used them in the Patty Hearst kidnapping, etc. I talked to the crew chief, who told me that if one flew over in the dark about 50 feet overhead, all you'd hear was about the same as a flock of birds at that height, like ducks or geese, not honking.

NASA has or had one of the final versions, 3 paddle blade wood prop, to carry microphones to test helicopter noise, flown in close formation. Based at an old (Moffat?) Navy airfield at the south end of the San Francisco Bay.