A fundamental principle of aeronautical engineering has been overturned

Post by stackghost » Mon, May 25, 2026, 3:53 AM UTC

aeternum wrote: post #43

Maarten88 wrote: post #34

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 surprisi…

I 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.

Post by mike_hock » Mon, May 25, 2026, 3:59 AM UTC

otterdude wrote: post #55

Maarten88 wrote: post #34

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 surprisi…

The core tenant of the paper is that roughness reduces drag IN the transition zone. A very small region of the total flow. Thats the region between laminar and turbulent flow. Laminar flow is typically 5x less drag than turbulent, and will be encountered about a Reynolds number of 500K-1M (ratio of inertial flow to viscous flow). Surfboards will have a Reynolds number of 10^7 which is entirely turbulent. A Cessna air…

Post by nmstoker » Mon, May 25, 2026, 4:15 AM UTC

mlmonkey wrote: post #9

> 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?

Post by gregman1 » Mon, May 25, 2026, 4:43 AM UTC

Groxx wrote: post #31

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 spee…

Post by adas0693 » Mon, May 25, 2026, 5:10 AM UTC