Undulating Skin Results In 50% Less Drag

[Larry Dighera]

If this technique can be adapted to gliders and other aircraft,
imagine the enabling effect it will produce:



http://technology.newscientist.com/channel/tech/dn13693-shapeshifting-skin-to-reduce-drag-on-planes-and-subs.html
Shape-shifting skin to reduce drag on planes and subs

* 13:30 16 April 2008
* NewScientist.com news service
* Colin Barras

Engineers have shown skin able to tune its wrinkles could cut
dramatically cut drag on submarines or planes (Image: IOP)
Engineers have shown skin able to tune its wrinkles could cut
dramatically cut drag on submarines or planes (Image: IOP)

Aircraft or submarines covered with an undulating skin able to
change at a flick of a button would experience 50% less drag than
conventional vehicles. This trick, which naturally occurs in
dolphins, is now being tested by human engineers.

Turbulence is the bane of engineers' lives. Chaotic air flow sets
up unstable vortices and patterns in gases and liquids, increasing
friction and drag.

Giving craft skin than can tweak its surface to impose order on
these currents could dramatically cut the effect of drag, says
Dimitris Lagoudas at Texas A&M University, US. Calming the chaotic
waves makes them interact less with the skin. "The particles in
the fluid stop "speaking" to the craft’s surface," he says.

Lagoudas and colleagues have worked out that wrinkling the surface
of a craft in the right way can cut problems. The surface must
assume the shape of the ideal ordered surface wave it is trying to
create, something that changes at different velocities.

Dolphin trick

It might seem counterintuitive to reduce drag by wrinkling the
surface of a craft, but nature provides a precedent. "Dolphins
induce their skin to wrinkle, so water won’t stick to them," says
Lagoudas.

After calculating that this approach would work, his team tested
designs for an "active skin" that shifts to ...

More...
http://technology.newscientist.com/channel/tech/dn13693-shapeshifting-skin-to-reduce-drag-on-planes-and-subs.html

[es330td]

On Apr 21, 12:57*pm, Larry Dighera > wrote:
> If this technique can be adapted to gliders and other aircraft,
> imagine the enabling effect it will produce:
>
> http://technology.newscientist.com/channel/tech/dn13693-shapeshifting...
> * * * * Shape-shifting skin to reduce drag on planes and subs
>
> * * * * * 13:30 16 April 2008
> * * * * * NewScientist.com news service
> * * * * * Colin Barras
>
> * * Engineers have shown skin able to tune its wrinkles could cut
> * * dramatically cut drag on submarines or planes (Image: IOP)
> * * Engineers have shown skin able to tune its wrinkles could cut
> * * dramatically cut drag on submarines or planes (Image: IOP)
>
> * * Aircraft or submarines covered with an undulating skin able to
> * * change at a flick of a button would experience 50% less drag than
> * * conventional vehicles. This trick, which naturally occurs in
> * * dolphins, is now being tested by human engineers.
>
> * * Turbulence is the bane of engineers' lives. Chaotic air flow sets
> * * up unstable vortices and patterns in gases and liquids, increasing
> * * friction and drag.
>
> * * Giving craft skin than can tweak its surface to impose order on
> * * these currents could dramatically cut the effect of drag, says
> * * Dimitris Lagoudas at Texas A&M University, US. Calming the chaotic
> * * waves makes them interact less with the skin. "The particles in
> * * the fluid stop "speaking" to the craft’s surface," he says.
>
> * * Lagoudas and colleagues have worked out that wrinkling the surface
> * * of a craft in the right way can cut problems. The surface must
> * * assume the shape of the ideal ordered surface wave it is trying to
> * * create, something that changes at different velocities.
>
> * * Dolphin trick
>
> * * It might seem counterintuitive to reduce drag by wrinkling the
> * * surface of a craft, but nature provides a precedent. "Dolphins
> * * induce their skin to wrinkle, so water won’t stick to them," says
> * * Lagoudas.
>
> * * After calculating that this approach would work, his team tested
> * * designs for an "active skin" that shifts to ...
>
> More...http://technology.newscientist.com/channel/tech/dn13693-shapeshifting...

Yesterday I was talking about something like this with my CFI and we
discussed the idea of dimpling an airplane like a golf ball. The
upper surfaces of the wings would remain smooth but the fuselage and
undersides of the wing would be dimpled to reduce drag.

[Big John]

On Mon, 21 Apr 2008 16:57:03 GMT, Larry Dighera >
wrote:

>
>If this technique can be adapted to gliders and other aircraft,
>imagine the enabling effect it will produce:
>
>
>
>http://technology.newscientist.com/channel/tech/dn13693-shapeshifting-skin-to-reduce-drag-on-planes-and-subs.html
> Shape-shifting skin to reduce drag on planes and subs
>
> * 13:30 16 April 2008
> * NewScientist.com news service
> * Colin Barras
>
> Engineers have shown skin able to tune its wrinkles could cut
> dramatically cut drag on submarines or planes (Image: IOP)
> Engineers have shown skin able to tune its wrinkles could cut
> dramatically cut drag on submarines or planes (Image: IOP)
>
> Aircraft or submarines covered with an undulating skin able to
> change at a flick of a button would experience 50% less drag than
> conventional vehicles. This trick, which naturally occurs in
> dolphins, is now being tested by human engineers.
>
> Turbulence is the bane of engineers' lives. Chaotic air flow sets
> up unstable vortices and patterns in gases and liquids, increasing
> friction and drag.
>
> Giving craft skin than can tweak its surface to impose order on
> these currents could dramatically cut the effect of drag, says
> Dimitris Lagoudas at Texas A&M University, US. Calming the chaotic
> waves makes them interact less with the skin. "The particles in
> the fluid stop "speaking" to the craft’s surface," he says.
>
> Lagoudas and colleagues have worked out that wrinkling the surface
> of a craft in the right way can cut problems. The surface must
> assume the shape of the ideal ordered surface wave it is trying to
> create, something that changes at different velocities.
>
> Dolphin trick
>
> It might seem counterintuitive to reduce drag by wrinkling the
> surface of a craft, but nature provides a precedent. "Dolphins
> induce their skin to wrinkle, so water won’t stick to them," says
> Lagoudas.
>
> After calculating that this approach would work, his team tested
> designs for an "active skin" that shifts to ...
>
>More...
>http://technology.newscientist.com/channel/tech/dn13693-shapeshifting-skin-to-reduce-drag-on-planes-and-subs.html

************************************************** ************
Didn't one or more of the America's Cup sail boats have something like
this in one of the last sail off's?

Big John

[Capt. Geoffrey Thorpe]

"es330td" > wrote in message
...
<...>

Yesterday I was talking about something like this with my CFI and we
discussed the idea of dimpling an airplane like a golf ball. The
upper surfaces of the wings would remain smooth but the fuselage and
undersides of the wing would be dimpled to reduce drag.

.................................................. .............................................

That only works on roundish things (helps keep the boundry layer attached as
you start around the back) and only for a limited range of reynolds numbers.
It won't work for your fuselage or the bottom of the wings.
Might work for round gear legs depending on the diameter and your airspeed.

Sailplanes do use "turbulator" tape to keep the boundry attached, but it is
applied only at specific locations.

--
Geoff
The Sea Hawk at Wow Way d0t Com
remove spaces and make the obvious substitutions to reply by mail
When immigration is outlawed, only outlaws will immigrate.

[Bertie the Bunyip[_24_]]

"Capt. Geoffrey Thorpe" <The Sea Hawk At Wow Way D0t C0m> wrote in
news:FuydnYfqHpzOvJDVnZ2dnUVZ_remnZ2d@wideopenwest .com:

> "es330td" > wrote in message
> .
> .. <...>
>
> Yesterday I was talking about something like this with my CFI and we
> discussed the idea of dimpling an airplane like a golf ball. The
> upper surfaces of the wings would remain smooth but the fuselage and
> undersides of the wing would be dimpled to reduce drag.
>

There's tape you can get for airplanes as well. It's aplied to the upper
surface of wings, in fact, as well as struts and just about anything else
you care to stick it to, even props.


Bertie

[Maxwell[_2_]]

"Bertie the Bunyip" > wrote in message
...
> "Capt. Geoffrey Thorpe" <The Sea Hawk At Wow Way D0t C0m> wrote in
> news:FuydnYfqHpzOvJDVnZ2dnUVZ_remnZ2d@wideopenwest .com:
>
>> "es330td" > wrote in message
>> .
>> .. <...>
>>
>> Yesterday I was talking about something like this with my CFI and we
>> discussed the idea of dimpling an airplane like a golf ball. The
>> upper surfaces of the wings would remain smooth but the fuselage and
>> undersides of the wing would be dimpled to reduce drag.
>>
>
> There's tape you can get for airplanes as well. It's aplied to the upper
> surface of wings, in fact, as well as struts and just about anything else
> you care to stick it to, even props.
>
>
> Bertie

[Bertie the Bunyip[_25_]]

"Maxwell" <luv2^fly99@cox.^net> wrote in
:

>
> "Bertie the Bunyip" > wrote in message
> ...
>> "Capt. Geoffrey Thorpe" <The Sea Hawk At Wow Way D0t C0m> wrote in
>> news:FuydnYfqHpzOvJDVnZ2dnUVZ_remnZ2d@wideopenwest .com:
>>
>>> "es330td" > wrote in message
>>> news:991c8471-6955-4565-890e-167de27c4999
@m36g2000hse.googlegroups.co
>>> m. .. <...>
>>>
>>> Yesterday I was talking about something like this with my CFI and we
>>> discussed the idea of dimpling an airplane like a golf ball. The
>>> upper surfaces of the wings would remain smooth but the fuselage and
>>> undersides of the wing would be dimpled to reduce drag.
>>>
>>
>> There's tape you can get for airplanes as well. It's aplied to the
>> upper surface of wings, in fact, as well as struts and just about
>> anything else you care to stick it to, even props.
>>
>>
>> Bertie
>
>
>



Snort!

God you're dummmmmmmm.


Bertie

[Bertie the Bunyip[_25_]]

"Maxwell" <luv2^fly99@cox.^net> wrote in news:%N9Pj.57906$QC.44358
@newsfe20.lga:

>
> "Bertie the Bunyip" > wrote in message
> ...
>> "Maxwell" <luv2^fly99@cox.^net> wrote in
>> :
>>
>>>
>>> "Bertie the Bunyip" > wrote in message
>>> ...
>>>> "Capt. Geoffrey Thorpe" <The Sea Hawk At Wow Way D0t C0m> wrote in
>>>> news:FuydnYfqHpzOvJDVnZ2dnUVZ_remnZ2d@wideopenwest .com:
>>>>
>>>>> "es330td" > wrote in message
>>>>> news:991c8471-6955-4565-890e-167de27c4999
>> @m36g2000hse.googlegroups.co
>>>>> m. .. <...>
>>>>>
>>>>> Yesterday I was talking about something like this with my CFI and
we
>>>>> discussed the idea of dimpling an airplane like a golf ball. The
>>>>> upper surfaces of the wings would remain smooth but the fuselage
and
>>>>> undersides of the wing would be dimpled to reduce drag.
>>>>>
>>>>
>>>> There's tape you can get for airplanes as well. It's aplied to the
>>>> upper surface of wings, in fact, as well as struts and just about
>>>> anything else you care to stick it to, even props.
>>>>
>>>>
>>>> Bertie
>>>
>>>
>>>
>>
>>
>>
>> Snort!
>>
>> God you're dummmmmmmm.
>>
>>
>> Bertie
>
>
>

Real dummmm.


Bertie

[Maxwell[_2_]]

"Bertie the Bunyip" > wrote in message
...
> "Maxwell" <luv2^fly99@cox.^net> wrote in
> :
>
>>
>> "Bertie the Bunyip" > wrote in message
>> ...
>>> "Capt. Geoffrey Thorpe" <The Sea Hawk At Wow Way D0t C0m> wrote in
>>> news:FuydnYfqHpzOvJDVnZ2dnUVZ_remnZ2d@wideopenwest .com:
>>>
>>>> "es330td" > wrote in message
>>>> news:991c8471-6955-4565-890e-167de27c4999
> @m36g2000hse.googlegroups.co
>>>> m. .. <...>
>>>>
>>>> Yesterday I was talking about something like this with my CFI and we
>>>> discussed the idea of dimpling an airplane like a golf ball. The
>>>> upper surfaces of the wings would remain smooth but the fuselage and
>>>> undersides of the wing would be dimpled to reduce drag.
>>>>
>>>
>>> There's tape you can get for airplanes as well. It's aplied to the
>>> upper surface of wings, in fact, as well as struts and just about
>>> anything else you care to stick it to, even props.
>>>
>>>
>>> Bertie
>>
>>
>>
>
>
>
> Snort!
>
> God you're dummmmmmmm.
>
>
> Bertie

[Capt. Geoffrey Thorpe]

"Bertie the Bunyip" > wrote in message
...
> "Capt. Geoffrey Thorpe" <The Sea Hawk At Wow Way D0t C0m> wrote in
> news:FuydnYfqHpzOvJDVnZ2dnUVZ_remnZ2d@wideopenwest .com:
>
>> "es330td" > wrote in message
>> .
>> .. <...>
>>
>> Yesterday I was talking about something like this with my CFI and we
>> discussed the idea of dimpling an airplane like a golf ball. The
>> upper surfaces of the wings would remain smooth but the fuselage and
>> undersides of the wing would be dimpled to reduce drag.
>>
>
> There's tape you can get for airplanes as well. It's aplied to the upper
> surface of wings, in fact, as well as struts and just about anything else
> you care to stick it to, even props.
>
>
> Bertie

Gee, I think I mentioned turbulator tape. Didn't I...

But of course, some MXwannaboi trimmed off my entire reply. Hmmmmm

Now, can you explain to the class what effect sticking this tape to "just
about anything else you care to stick it to," is going to have on drag?

--
Geoff
The Sea Hawk at Wow Way d0t Com
remove spaces and make the obvious substitutions to reply by mail
When immigration is outlawed, only outlaws will immigrate.

[Capt. Geoffrey Thorpe]

"Big John" > wrote in message
...
<...>
>
> ************************************************** ************
> Didn't one or more of the America's Cup sail boats have something like
> this in one of the last sail off's?
>
> Big John
>


They have tried a textured surface (more than a couple races ago) but the
rules were changed again to outlaw this sort of thing (along with surface
tension modifiers that you drip into the water at the bow).

I don't believe that the "shape shifting" idea has been attempted in real
life - But you are right, it's not exactly a new idea.

--
Geoff
The Sea Hawk at Wow Way d0t Com
remove spaces and make the obvious substitutions to reply by mail
When immigration is outlawed, only outlaws will immigrate.

[Bertie the Bunyip[_24_]]

"Capt. Geoffrey Thorpe" <The Sea Hawk At Wow Way D0t C0m> wrote in
news:vJSdnYfBN9CF2pDVnZ2dnUVZ_gudnZ2d@wideopenwest .com:

> "Bertie the Bunyip" > wrote in message
> ...
>> "Capt. Geoffrey Thorpe" <The Sea Hawk At Wow Way D0t C0m> wrote in
>> news:FuydnYfqHpzOvJDVnZ2dnUVZ_remnZ2d@wideopenwest .com:
>>
>>> "es330td" > wrote in message
>>> news:991c8471-6955-4565-890e-167de27c4999
@m36g2000hse.googlegroups.co
>>> m. .. <...>
>>>
>>> Yesterday I was talking about something like this with my CFI and we
>>> discussed the idea of dimpling an airplane like a golf ball. The
>>> upper surfaces of the wings would remain smooth but the fuselage and
>>> undersides of the wing would be dimpled to reduce drag.
>>>
>>
>> There's tape you can get for airplanes as well. It's aplied to the
>> upper surface of wings, in fact, as well as struts and just about
>> anything else you care to stick it to, even props.
>>
>>
>> Bertie
>
> Gee, I think I mentioned turbulator tape. Didn't I...

Yes, but this stuff is different. it's perforated a-la golf ball as
opposed to the zig zag stuf they use on gliders.
>
> But of course, some MXwannaboi trimmed off my entire reply. Hmmmmm
>

Oh brother.


> Now, can you explain to the class what effect sticking this tape to
> "just about anything else you care to stick it to," is going to have
> on drag?
>


Well, the dimples form a very shallow turbulent layer that paadoxically
aids in the adherence of the boundary layer to the surface thus reducing
turbulence and as a result, drag as well.


Happy now or would you like me to call you a name as well?


Bertie

[Maxwell[_2_]]

"Bertie the Bunyip" > wrote in message
.. .
> "Capt. Geoffrey Thorpe" <The Sea Hawk At Wow Way D0t C0m> wrote in
> news:vJSdnYfBN9CF2pDVnZ2dnUVZ_gudnZ2d@wideopenwest .com:
>
>> "Bertie the Bunyip" > wrote in message
>> ...
>>> "Capt. Geoffrey Thorpe" <The Sea Hawk At Wow Way D0t C0m> wrote in
>>> news:FuydnYfqHpzOvJDVnZ2dnUVZ_remnZ2d@wideopenwest .com:
>>>
>>>> "es330td" > wrote in message
>>>> news:991c8471-6955-4565-890e-167de27c4999
> @m36g2000hse.googlegroups.co
>>>> m. .. <...>
>>>>
>>>> Yesterday I was talking about something like this with my CFI and we
>>>> discussed the idea of dimpling an airplane like a golf ball. The
>>>> upper surfaces of the wings would remain smooth but the fuselage and
>>>> undersides of the wing would be dimpled to reduce drag.
>>>>
>>>
>>> There's tape you can get for airplanes as well. It's aplied to the
>>> upper surface of wings, in fact, as well as struts and just about
>>> anything else you care to stick it to, even props.
>>>
>>>
>>> Bertie
>>
>> Gee, I think I mentioned turbulator tape. Didn't I...
>
> Yes, but this stuff is different. it's perforated a-la golf ball as
> opposed to the zig zag stuf they use on gliders.
>>
>> But of course, some MXwannaboi trimmed off my entire reply. Hmmmmm
>>
>
> Oh brother.
>
>
>> Now, can you explain to the class what effect sticking this tape to
>> "just about anything else you care to stick it to," is going to have
>> on drag?
>>
>
>
> Well, the dimples form a very shallow turbulent layer that paadoxically
> aids in the adherence of the boundary layer to the surface thus reducing
> turbulence and as a result, drag as well.
>
>

Totally incorrect, Bertie Buttlick.

[Bertie the Bunyip[_25_]]

"Maxwell" <luv2^fly99@cox.^net> wrote in news:WSbPj.110302$Ft5.69371
@newsfe15.lga:

>
> "Bertie the Bunyip" > wrote in message
> .. .
>> "Capt. Geoffrey Thorpe" <The Sea Hawk At Wow Way D0t C0m> wrote in
>> news:vJSdnYfBN9CF2pDVnZ2dnUVZ_gudnZ2d@wideopenwest .com:
>>
>>> "Bertie the Bunyip" > wrote in message
>>> ...
>>>> "Capt. Geoffrey Thorpe" <The Sea Hawk At Wow Way D0t C0m> wrote in
>>>> news:FuydnYfqHpzOvJDVnZ2dnUVZ_remnZ2d@wideopenwest .com:
>>>>
>>>>> "es330td" > wrote in message
>>>>> news:991c8471-6955-4565-890e-167de27c4999
>> @m36g2000hse.googlegroups.co
>>>>> m. .. <...>
>>>>>
>>>>> Yesterday I was talking about something like this with my CFI and
we
>>>>> discussed the idea of dimpling an airplane like a golf ball. The
>>>>> upper surfaces of the wings would remain smooth but the fuselage
and
>>>>> undersides of the wing would be dimpled to reduce drag.
>>>>>
>>>>
>>>> There's tape you can get for airplanes as well. It's aplied to the
>>>> upper surface of wings, in fact, as well as struts and just about
>>>> anything else you care to stick it to, even props.
>>>>
>>>>
>>>> Bertie
>>>
>>> Gee, I think I mentioned turbulator tape. Didn't I...
>>
>> Yes, but this stuff is different. it's perforated a-la golf ball as
>> opposed to the zig zag stuf they use on gliders.
>>>
>>> But of course, some MXwannaboi trimmed off my entire reply. Hmmmmm
>>>
>>
>> Oh brother.
>>
>>
>>> Now, can you explain to the class what effect sticking this tape to
>>> "just about anything else you care to stick it to," is going to
have
>>> on drag?
>>>
>>
>>
>> Well, the dimples form a very shallow turbulent layer that
paadoxically
>> aids in the adherence of the boundary layer to the surface thus
reducing
>> turbulence and as a result, drag as well.
>>
>>
>
> Totally incorrect, Bertie Buttlick.
>

Nope.


Bertie
>
>

[Capt. Geoffrey Thorpe]

"Bertie the Bunyip" > wrote in message
.. .
> "Capt. Geoffrey Thorpe" <The Sea Hawk At Wow Way D0t C0m> wrote in
> news:vJSdnYfBN9CF2pDVnZ2dnUVZ_gudnZ2d@wideopenwest .com:
>
<...>
>> Now, can you explain to the class what effect sticking this tape to
>> "just about anything else you care to stick it to," is going to have
>> on drag?
>>
>
>
> Well, the dimples form a very shallow turbulent layer that paadoxically
> aids in the adherence of the boundary layer to the surface thus reducing
> turbulence and as a result, drag as well.
>

So if I stick this on my propeller (or "just about anything else you care
to stick it to," ) I am going to reduce drag?


--
Geoff
The Sea Hawk at Wow Way d0t Com
remove spaces and make the obvious substitutions to reply by mail
When immigration is outlawed, only outlaws will immigrate.

[Larry Dighera]

On Mon, 21 Apr 2008 14:31:15 -0500, Big John >
wrote in >:

>Didn't one or more of the America's Cup sail boats have something like
>this in one of the last sail off's?

Is this it?


http://www.newscientist.com/article/mg15320654.400-secrets-of-a-perfect-skin.html
Researchers have known for years that fast-swimming sharks are
covered with renewable scales, called dermal denticles, that have
microscopic ridges. Just what these ridges did was a mystery until
the 1980s when specialists in aerodynamics developed a way of
smoothing turbulent flow using microscopic surface grooves that
are aligned with the movement of fluid. These grooves are called
riblets. "There are very close connections between riblets and
shark skins," says Kwing-So Choi, a mechanical engineer at the
University of Nottingham specialising in drag reduction.

Riblets work by making turbulence more ordered near the surface.
"They are like tiny fences that prevent the lateral movement of
turbulence across the flow," says Choi. While any lateral movement
is hindered, any flow that is parallel with the riblets continues
unabated. "If you optimise the size and shape of the riblets, a
drag reduction of up to 10 per cent is possible."

Riblets have already been tested in real applications. Their
biggest claim to fame was as a putative contributor to the sailing
coup in 1987 when the US won the America's Cup, the prestigious
yachting trophy. The American boat had a riblet coating on its
hull, a development that was later banned by race officials. Other
mariners have been slow to follow suit because riblets are easily
clogged by microscopic marine debris. A more promising application
is in aircraft, where fouling is less of a problem. Such riblets
are already in use on some commercial airliners.


It sounds different from the active skin in the more recent article.

[Bertie the Bunyip[_24_]]

"Capt. Geoffrey Thorpe" <The Sea Hawk At Wow Way D0t C0m> wrote in
:

> "Bertie the Bunyip" > wrote in message
> .. .
>> "Capt. Geoffrey Thorpe" <The Sea Hawk At Wow Way D0t C0m> wrote in
>> news:vJSdnYfBN9CF2pDVnZ2dnUVZ_gudnZ2d@wideopenwest .com:
>>
> <...>
>>> Now, can you explain to the class what effect sticking this tape to
>>> "just about anything else you care to stick it to," is going to
>>> have on drag?
>>>
>>
>>
>> Well, the dimples form a very shallow turbulent layer that
>> paadoxically aids in the adherence of the boundary layer to the
>> surface thus reducing turbulence and as a result, drag as well.
>>
>
> So if I stick this on my propeller (or "just about anything else you
> care to stick it to," ) I am going to reduce drag?
>
>

Apparently. I have an article about it somewhere. the prop installation
was problematic and not STC'd for certified aircraft. It tended to peel,
apparently. They were featured in Sport Aviation a few years ago.


Bertie

[Bertie the Bunyip[_24_]]

Larry Dighera > wrote in
:

> On Mon, 21 Apr 2008 14:31:15 -0500, Big John >
> wrote in >:
>
>>Didn't one or more of the America's Cup sail boats have something like
>>this in one of the last sail off's?
>
> Is this it?
>
>
> http://www.newscientist.com/article/mg15320654.400-secrets-of-a-
perfect
> -skin.html
> Researchers have known for years that fast-swimming sharks are
> covered with renewable scales, called dermal denticles, that have
> microscopic ridges. Just what these ridges did was a mystery until
> the 1980s when specialists in aerodynamics developed a way of
> smoothing turbulent flow using microscopic surface grooves that
> are aligned with the movement of fluid. These grooves are called
> riblets. "There are very close connections between riblets and
> shark skins," says Kwing-So Choi, a mechanical engineer at the
> University of Nottingham specialising in drag reduction.
>
> Riblets work by making turbulence more ordered near the surface.
> "They are like tiny fences that prevent the lateral movement of
> turbulence across the flow," says Choi. While any lateral movement
> is hindered, any flow that is parallel with the riblets continues
> unabated. "If you optimise the size and shape of the riblets, a
> drag reduction of up to 10 per cent is possible."
>
> Riblets have already been tested in real applications. Their
> biggest claim to fame was as a putative contributor to the sailing
> coup in 1987 when the US won the America's Cup, the prestigious
> yachting trophy. The American boat had a riblet coating on its
> hull, a development that was later banned by race officials. Other
> mariners have been slow to follow suit because riblets are easily
> clogged by microscopic marine debris. A more promising application
> is in aircraft, where fouling is less of a problem. Such riblets
> are already in use on some commercial airliners.
>
>
> It sounds different from the active skin in the more recent article.
>

It is and it isn't. The riblets on shark skins are more closely related
to vortex generators.



Bertie