http://www.physorg.com/news11095.html
eeehm. Isn"t this the reason why golf balls look like they had a rough puberty with a problematic skin?
Perhaps the "rough" shark-skin type swimsuits and under-water surface treatments use the same physics. If so, somebody should have figured this out a long time ago!
We were studying this phenomenon in wind tunnels in the early 1980s
in our University classes. Announcing this as a huge breakthrough
is akin to someone announcing the discovery of the wheel....
in our University classes. Announcing this as a huge breakthrough
is akin to someone announcing the discovery of the wheel....
Hello all
The B-52 bomber built in the 50's has devices on the stabilator called vortex generators which are used to prevent laminar airflow separation.
The B-52 bomber built in the 50's has devices on the stabilator called vortex generators which are used to prevent laminar airflow separation.
I remember reading about this in Popular Science or Mechanics years ago. Perhaps the Swedes could all pitch in and get a supscription.
Cutter
Cutter
QUOTE
The B-52 bomber built in the 50's has devices on the stabilator called vortex generators which are used to prevent laminar airflow separation.
Looked up vertex generators on wikipedia. Certainly didn't seem to be the same thing at all.. But what do I know.
From the abstract of the article.
It sounds like this isn't the same thing as:
It sounds like this isn't the same thing as:
Perhaps the "rough" shark-skin type swimsuits and under-water surface treatments use the same physics. If so, somebody should have figured this out a long time ago!
This is starting to be like slashdot, people not reading the actual article and then stating that this is nothing new, or stupid, or whatever.
They probably stole this idea from aliens
QUOTE
Reducing skin friction is important in nature and in many technological applications. This reduction may be achieved by reducing stresses in turbulent boundary layers, for instance tailoring biomimetic rough skins. Here we take a second approach consisting of keeping the boundary layer laminar as long as possible by forcing small optimal perturbations. Because of the highly non-normal nature of the underlying linearized operator, these perturbations are highly amplified and able to modify the mean velocity profiles at leading order. We report results of wind-tunnel experiments in which we implement this concept by using suitably designed roughness elements placed on the skin to enforce nearly optimal perturbations. We show that by using this passive control technique it is possible to sensibly delay transition to turbulence.
It sounds like this isn't the same thing as:
QUOTE (->
| QUOTE |
| Reducing skin friction is important in nature and in many technological applications. This reduction may be achieved by reducing stresses in turbulent boundary layers, for instance tailoring biomimetic rough skins. Here we take a second approach consisting of keeping the boundary layer laminar as long as possible by forcing small optimal perturbations. Because of the highly non-normal nature of the underlying linearized operator, these perturbations are highly amplified and able to modify the mean velocity profiles at leading order. We report results of wind-tunnel experiments in which we implement this concept by using suitably designed roughness elements placed on the skin to enforce nearly optimal perturbations. We show that by using this passive control technique it is possible to sensibly delay transition to turbulence. |
It sounds like this isn't the same thing as:
Perhaps the "rough" shark-skin type swimsuits and under-water surface treatments use the same physics. If so, somebody should have figured this out a long time ago!
This is starting to be like slashdot, people not reading the actual article and then stating that this is nothing new, or stupid, or whatever.
They probably stole this idea from aliens
I remember reading about reducing resistance with an irregular surface from Viktor Schauberger's works. I agree this shouldn't be publicized as some break-through if it's been around for so long. It could be mentioned as a good thing to be picked up after neglecting it for so long, tough.
Forgot to mention that from what I remember and understood, what reduces the friction, is not the actual rough surface, but this surface cause small turbulence that creates a sort of isolation from it, with a much reduced friction than the solid surface. It probably works as a flat board dragged on the floor compared to one on a layer of ping-pong balls.
Model airplane builder - the ones that do really slow flying gliders - know for ages that creating a row of small bumps some distance from the leading edge of the top of the wing can prevent stalling at low air speeds. They got the trick from owls, who have a row of hairy feathers at the same location. Keeps airflow laminar and prevents besides stalling also noise. Rudimentary biology and simple glider models must have missed Sweden.
Above is a typical response of Americans they think everything has been discovered there,little do they know.
Perhaps the "gringos" could be less obnoxious and cocky about the subject.
wow.......seems late to be discovering and implemented this advancement in design.....engineers must work with profit as main protocol.
Do you guys ever look at airplanes and think that engineers could do better?
wow....i want those on my car......and my bike helmet....
Do you guys ever look at airplanes and think that engineers could do better?
wow....i want those on my car......and my bike helmet....
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