A fundamental principle of aeronautical engineering has been overturned

Any 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.

> 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?

It'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.

If 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.

https://archive.ph/DbcqV

I'll await the experimental measurements of fuel efficiency using real aircraft.

Tell that to the ice build up on the wing.

Uhh. 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.

I 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…

This 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.