Comment by otterdude
15 hours ago
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 aircraft will have a Reynolds number of 1-5x10^6.
> Surfboards will have a Reynolds number of 10^7 which is entirely turbulent.
A fin, foil or daggerboard below the board/boat is operating well within the range of Reynolds' numbers where laminar flow is relevant.
> core tenant
And Lady Mondegreen.
Tenet is the word you mean
swoosh swoosh - that's the sound of things traversing backward in time.