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A fundamental principle of aeronautical engineering has been overturned
- philip1209 5mo agoFascinating. I wonder what the implications for radar-absorbing finishes are. Could they be more aerodynamic already?
- littlexsparkee 5mo agohttps://archive.ph/DbcqV https://archive.ph/DbcqV
- bediger4000 5mo agoThis article is kind of false. Keeping an object's boundary layer attached is known to reduce drag, even if the flow is turbulent. Golf ball dimples are a successful attempt to keep boundary layers attached.
- toss1 5mo agoYes, but this is not that. Golf ball dimples are about 4 mm across and 0.2mm or 200μm (micrometers). These features are several orders of magnitude smaller at 38 to 53μm diameter. >>the first in the world to demonstrate that aerodynamic drag can be reduced by up to 43.6 percent simply by applying distributed micro-roughness (DMR), a surface roughness so fine and irregular that it cannot be distinguished by the naked eye. [...] Two types of DMRs were used in this experiment: A convex pattern made of glass beads with diameters ranging from 38 to 53 micrometers (μm) and a concave pattern applied by sandblasting. The height of the DMR coating is only 1 percent of the thickness of the boundary layer and is classified as a “smooth surface” from a hydrodynamic point of view.
- nullhole 5mo agoNot to be that guy, but 38-53um is 1 order of magnitude smaller than 200um
- toss1 5mo agoNot to be that guy ;-) , but the diameter of the golf ball dimples is ~4 mm or about 4,000 μm, whilst the diameter of the spheres is 38-53 μm, or about 0.04 mm. Diameter-to-diameter seems like about 100x or two orders of magnitude? Similarly, 200 μm is the golf ball dimple depth (oops, just noticed I dropped that key word), and they didn't give us a measurement of the depth of the dents caused by the spheres or sandblasting, but it would likely be significantly less than half the radius of the spheres? Sorry about misleading with dropping the "depth" word.
- staplung 5mo agoThe headline is perhaps overstating things a bit but they do discuss how this is different than e.g. rivulets ''' This technology is fundamentally different from the “rivulet (shark skin) process,” which is known as a typical aerodynamic drag reduction technology. The rivulet process mimics the fine longitudinal grooves in shark skin, and by carving grooves approximately 0.1 mm wide along the direction of airflow, it aligns the vortices that occur near the wall surface of turbulent airflow areas. DMR, on the other hand, delays the switch from laminar to turbulent flow by means of random and minute irregularities. The flow zones it affects and the mechanisms it employs are based on completely different concepts. '''
- doginasuit 5mo ago"We apologize for the mistake in overturning a fundamental principle of aeronautical engineering, those responsible have now been sacked."
- deleted 5mo ago[deleted]
- sgc 5mo agoIf the application method is as rudimentary as sandblasting, it sounds rather simple to retrofit to existing aircraft. If it works as they state it does, it's a virtually free same-day fuel efficiency boost. However, I did not see what the actual net improvement was. When they talk percentages, they are talking only about "in the transition zone". They say the coefficient improves throughout, but in theory, it could be almost irrelevant if the overall improvement throughout the profile is close to 0. It also sounds like a very difficult level of precise degradation to maintain for any period of time in real world conditions, since it would be easy to clog or abrade further.
- imoverclocked 5mo ago… theoretically meets reality pretty quick in aviation. You’ll likely find a lot of red tape to modifying any particular aircraft until it has been tested or certified. Well, for certified aircraft anyway. Even in the experimental world you might find some (excuse the pun) resistance to sand blasting someone’s wing.
- zonkerdonker 5mo agoBased on the mechanism of flow attachment in the transition zone it seems like the overall airfoil profile would likely have to change to take full advantage of the reduced friction. I think its much more likely to see this technique played with somewhere like Formula 1, if it hasnt been already.
- russellbeattie 5mo ago> "...like Formula 1" Or projectiles like bullets and missiles. A sniper bullet with nanoscale textured surface that's able to go x% farther due to reduced drag seems plausible.
- TomatoCo 5mo agoOn a metal as soft as copper I imagine that texture'll last about 30 minutes after it's issued to the soldier.
- mlmonkey 5mo ago> It's long been accepted that the smoother the surface, the lower the aerodynamic drag. That turns out not always to be the case. Huh... I'd always heard that a golf ball's dimples help reduce drag?
- dathinab 5mo agoyep and a lot of "smooth" aerodynamic surfaces have "microscopic"/"very small" surface patterns to make the surface less perfect smooth as if it is too perfect smooth the air kinda "sticks" to it increasing drag (to say it in a very unscientific way)
- pfdietz 5mo ago[dead]
- beering 5mo agoTFA makes it clear that this is a very different phenomenon than golf ball dimples, and even goes as far as to say they are opposing.
- coldtea 5mo agoHowever the TFA doesn't make clear that this: "It's long been accepted that the smoother the surface, the lower the aerodynamic drag. That turns out not always to be the case" was already known to NOT always be the case (e.g. in golf balls).
- Swizec 5mo ago> Huh... I'd always heard that a golf ball's dimples help reduce drag? Yep also vortex generators in cars have become common. So common that they've filtered down to after market parts you can put on a honda civic Vortexes break up large air pockets and reduce drag.
- SilverElfin 5mo agoIs that what those things are on random civics? Do they make any difference for regular street cars?
- adverbly 5mo agoI'll await the experimental measurements of fuel efficiency using real aircraft.
- drpixie 5mo agoMe too. The number of "revolutionary" designs that are announced but disappear makes me cynical. Looking wings on real aircraft, unless freshly painted, they're pretty close to finely sanded :) If the airlines and engineers saw a significant performance degradation with wear, they'd be out there polishing and repainting wings. On a similar note - How many times have you seen announcements about someones blended wing that is going to save 50% fuel? But there are very few blended wings in nature (eg. rays), and those are in a very slow-speed regime.
- dnautics 5mo agoThe real obstacle to blended wing designs, I imagine, is more boring: airports are likely to be difficult to retrofit to support those, well for cargo anyways, and for passengers there's probably less appetite to board such a plane
- dnautics 5mo agoIs this not useful in the speed regime of automobiles?
- 6stringmerc 5mo agoI wrote about this ages ago, in that shark skin is an evolutionary adaptation worth study because water is thicker than air, but when air compounds, blah blah blah. Basically think of making a composite mold with directional tiny tiny dorsal fin looking surface. If you rub your hand on it the wrong way it cuts you open. Could even be scaled for large cargo ship hulls. Next up: my personal wing invention which uses leading edges modeled on humpback whale fins, because the use case / stall profile is better. Sigh, I’m going to have a great time in Heaven chatting with Leonardo da Vinci…
- r3trohack3r 5mo agoFrom the featured article: > This technology is fundamentally different from the “rivulet (shark skin) process,” which is known as a typical aerodynamic drag reduction technology. The rivulet process mimics the fine longitudinal grooves in shark skin, and by carving grooves approximately 0.1 mm wide along the direction of airflow, it aligns the vortices that occur near the wall surface of turbulent airflow areas. DMR, on the other hand, delays the switch from laminar to turbulent flow by means of random and minute irregularities. The flow zones it affects and the mechanisms it employs are based on completely different concepts.
- wafflemaker 5mo agoWhy wait for heaven. There probably are mods for Kerbal Space Program with exactly that parts. Create your wingsuit there.
- spacedoutman 5mo ago>humpback whale fins you might find this video interesting then, the fastest rc drone in the world and it uses humpback inspired props. https://www.youtube.com/watch?v=k9n1h0rn9No https://www.youtube.com/watch?v=k9n1h0rn9No
- rawgabbit 5mo agoUhh. I was taught that in university in the late 80s. Some surfaces have a lot of friction and if you add surface imperfections the turbulent airflow actually reduces drag.
- clnhlzmn 5mo agoYou learned something different then because this finding is that some kinds of additional roughness delay the transition to turbulent flow which is pretty clear in the article.
- fsagx 5mo agohttps://phys.org/news/2014-01-smooth-rough-surfaces.html https://phys.org/news/2014-01-smooth-rough-surfaces.html A quick search looks to show the same general topic from more than a decade ago. I too have a recollection of this being discussed in the late 80s or early 90s. Maybe some folk wisdom that's just now getting quantified.
- rawgabbit 5mo agoThanks for clarifying.
- qwertyuiop_ 5mo agoTell that to the ice build up on the wing.
- joarv0249nw 5mo agoI was thinking the same. Ice build upp will probably increase with a bigger and rougher surface area
- Groxx 5mo agoIt's almost certainly my adblocker playing poorly with their "subscribe to read" stuff, but I had to lol at the failure mode. When I load the page, I get the splash image/headline, and below it: > Subscribe to listen [9 minutes] > Aerodynamic drag is a major “barrier” in high-speed airplanes, automobiles, and bullet trains. This is because a design with less aerodynamic drag allows the aircraft to move at higher speeds with less energy. And then just comments and links to other articles. No indication at all that there's more to the article beyond (apparently) an audio recording. This might explain some of the "didn't read the article" comments? Not that it doesn't happen anyway tho.
- gregman1 5mo agoSame stuff! I’d rather prefer some archive link or something. Some websites are a bit aggressive these days.
- gregman1 5mo agoIf you happened to know Japanese it’s much easier to read the original article on wiredjp than .com https://wired.jp/article/distributed-micro-roughness-aerodynamic-drag-reduction/ https://wired.jp/article/distributed-micro-roughness-aerodyn...
- bookofjoe 5mo agohttps://archive.ph/YwAky https://archive.ph/YwAky
- pwinwood 5mo agoSame happened to me but I opened it in reader view in Firefox and it's fine!
- littlexsparkee 5mo agoIf you're quick to hit the play button (it briefly says 'Listen' on page load) with page inspect open, you can get the audio link in the network tab.
- ryankrage77 5mo ago
- Maarten88 5mo agoAny competitive sailor or foil-racer knows that the underwater surface has the least friction and best laminar flow when sanded with fine-grid sandpaper, around 1000 to 1500 grid. It always surprised me that this was not true in air and airplane wings were supposedly best when glossy. So now it turns out that this is indeed not true, and airfoils also benefit from micro-roughness for lowest friction. Now the surprising question to me is how is it possible that something so simple was not known in this very well-researched and well-funded field. It probably was known, just not by the paper-publishing researchers.
- deleted 5mo ago[deleted]
- aeternum 5mo agoI wonder how quickly airlines will adopt sanded/rough wings. It's also interesting that the efficiency of winglets were known for quite awhile but only somewhat recently have nearly all airliners adopted them.
- rogerrogerr 5mo agoIt’s probably operationally easier to keep surfaces smooth than to keep them a specific amount of roughness.
- greggsy 5mo agoIt’s presumably easier to keep a smooth surface clear of bugs, dust and ice too.
- swasheck 5mo agoyeah. what are the effects of too much roughness? may be safer and easier to maintain at smooth than at a specific roughness spec
- delecti 5mo agoAlso matters a bit what happens to a surface that they don't do anything to. Does a precisely rough surface get too rough or too smooth? Does a precisely smooth surface get rougher in a way that's beneficial? Could be the case that in-practice this means they just worry less as their perfectly smooth planes get a bit rough.
- wizardforhire 5mo agoThis article and thread has got some major Tai’s Model vibes [1] [1] https://en.wikipedia.org/wiki/Tai%27s_model https://en.wikipedia.org/wiki/Tai%27s_model
- w10-1 5mo agoKlaus Savier is a longtime efficiency experimentalist, and opted for unpolished paint circa ~1990. His initial goal was weight reduction but numbers showed the finish had aerodynamic benefits. I'm intrigued by the methodology of the wind tunnel: using magnets to more precisely measure and to avoid interference from guy wires...
- tobadzistsini 5mo agoThis reminds me of the Dimple Car Experiment from Mythbusters.
- jdkee 5mo agoGolf balls.
- zabi_rauf 5mo agoAren’t Turbulators doing similar thing i.e. its keeps the boundary layer for longer before it totally turns into turbulent layer?
- deleted 5mo ago[deleted]
- mike_hock 5mo ago> You’ve read your last free article.
- charles_f 5mo agoYou can worked around that in Firefox by switching to focused reading
- deleted 5mo ago[deleted]
- adas0693 5mo agofyi: the paper cited in the wired article is at https://arxiv.org/abs/2603.23843 https://arxiv.org/abs/2603.23843
- dotancohen 5mo ago> The ... magnetic support balance system ... can levitate a streamlined model ... inside a wind tunnel without contact using electromagnetic force. That's pretty cool. Presumably the varying magnetic field strength required to suspend the test article is also an indicator of varying forces on the vehicle.
- deleted 5mo ago[deleted]
- brador 5mo agoDoes this same principle make the moon orbit a little faster?
- defrost 5mo agoWhat order of aerodynamic drag does our moon in orbit experience?
- Liftyee 5mo agoInteresting finding, but hardly fundamental. My fluids lectures taught that there's form drag ("pressure drag" in the article) and skin friction drag. The two trade off with each other depending on Reynolds number. Keeping the flow laminar reduces skin friction drag (suggesting smooth skin), but keeping the flow attached for longer (e.g. by inducing turbulence, or injecting air...) reduces form drag (at a cost of increased skin friction due to turbulence). Reads like they've discovered a neat way to delay flow separation while maintaining laminar flow, but the underlying principles have not changed. "Smooth thing low drag" was never a rule and only works at certain scales.
- wanderingmind 5mo agoThe actual paper: https://www.cambridge.org/core/journals/journal-of-fluid-mechanics/article/dmr-effect-on-drag-reduction-of-a-streamlined-body-measured-by-magnetic-suspension-and-balance-system/0E3FF950CCC66DEFCBA3D3DCD36CE2B6 https://www.cambridge.org/core/journals/journal-of-fluid-mec...
- hexobhi 5mo ago[flagged]
- golddust-gecko 5mo agoI feel like this part is either a mistake, or a whole story in itself: > This premise was based on the results of a 1940 study by Ichiro Tani, a Japanese scientist who demonstrated the relationship between surface roughness (an indicator of the state of the machined surface) and turbulent transition, arguing that surface roughness, which was unavoidable with the manufacturing technology of the time, prevented laminar flow from being realized. > However, in 1989 Tani reinterpreted the experimental data on rough-surfaced pipes obtained by fluid engineer Johann Nikulase in the 1930s, suggesting that “roughness may not necessarily only promote turbulent transition and increase fluid resistance.” So if true, this means that Tani was working on the same problem for 49 years. Evidently [he died in 1990](https://www.wikidata.org/wiki/Q24868684 https://www.wikidata.org/wiki/Q24868684), so it's at least possible.
- librasteve 5mo agoballs! (golf balls)
- deleted 5mo ago[deleted]
- Soling20 5mo agoQuestion, should both sides of a lifting foil be the same of the same texture?
- felineflock 5mo agoAny chance golf ball dimples in the wings would make it better? In a golf ball, the dimples create a turbulence in a layer of air around it but results in higher lift due to smaller vortex and less drag.
- fnord77 5mo ago> Experimental results showed that the critical Reynolds number at which the turbulent transition begins increased from approximately 1.9 × 10⁶ to 2.2 × 10⁶ for the DMR-coated model, and drag was dramatically reduced by up to 43.6 percent in the transition zone.
- matt-attack 5mo agoI’d be curious to know if this sort of thing could’ve been predicted through computer modeling. And if not, does that mean, we have a gap in our fundamental fluid equations? And if so, couldn’t we just have a model iterate on different surface patterns and optimize?
- hyperbrainer 5mo agohttps://archive.is/20260524231039/https://www.wired.com/story/a-fundamental-principle-of-aeronautical-engineering-has-been-overturned/ https://archive.is/20260524231039/https://www.wired.com/stor...
- deleted 5mo ago[deleted]
- itissid 5mo agohttps://archive.ph/YwAky https://archive.ph/YwAky