Da Wired (link all'articolo alla fine, c'è un paywall, ma con un po' di buona volontà è leggibile). Non ho idea di quanto la cosa sia effettivamente applicabile e/o abbia un senso, ma mi sembrava interessante.
"For more than 80 years, a basic principle of aeronautical engineering has been that the surface of an object must be smooth in order to reduce aerodynamic drag. 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.” (In physics, air is considered a fluid.) Inheriting this idea, a research group led by Yasuaki Kohama of Tohoku University demonstrated in the 1990s that fibrous rough surfaces, which have fine fibrous irregularities on their surface, have the effect of delaying transition under certain conditions.
The same Tohoku University research team recently announced a discovery that significantly advances this idea. Aiko Yakino, associate professor at Tohoku University's Institute of Fluid Science, and her research group were 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."
www.wired.com
"For more than 80 years, a basic principle of aeronautical engineering has been that the surface of an object must be smooth in order to reduce aerodynamic drag. 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.” (In physics, air is considered a fluid.) Inheriting this idea, a research group led by Yasuaki Kohama of Tohoku University demonstrated in the 1990s that fibrous rough surfaces, which have fine fibrous irregularities on their surface, have the effect of delaying transition under certain conditions.
The same Tohoku University research team recently announced a discovery that significantly advances this idea. Aiko Yakino, associate professor at Tohoku University's Institute of Fluid Science, and her research group were 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."
A Fundamental Principle of Aeronautical Engineering Has Been Overturned
It’s long been accepted that the smoother the surface, the lower the aerodynamic drag. That turns out not always to be the case.
