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mlmonkey 7 hours 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?

djeastm 4 hours ago | parent | next [-]

From the article:

>This principle is fundamentally different from the effect of dimples on golf balls. Dimples reduce pressure resistance by intentionally turbulizing the airflow and suppressing backward separation. DMR, on the other hand, delays the transition, thereby suppressing not pressure resistance but the wall friction itself. They are opposite mechanisms.

degamad 41 minutes ago | parent [-]

mlmonkey did not say that this new observation was the same phenomenon as golf ball dimples, just golf ball dimples already disproved the "long accepted" belief that "smoother the surface, the lower the aerodynamic drag".

kazinator 13 minutes ago | parent [-]

Exactly; golf balls are one example of it not being accepted that smooth surfaces are always best for drag, regardless of how the new result works.

beering 6 hours ago | parent | prev | next [-]

TFA 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.

Swizec 6 hours ago | parent | prev | next [-]

> 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 5 hours ago | parent [-]

Is that what those things are on random civics? Do they make any difference for regular street cars?

16 minutes ago | parent | next [-]
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ungreased0675 5 hours ago | parent | prev [-]

I put some (actual, as in from an airplane parts catalog) vortex generators on my hybrid. It slightly increased gas mileage and slightly reduced noise.

The less aerodynamic the vehicle, the more noticeable the result will probably be.

cpncrunch 5 hours ago | parent | prev | next [-]

Read the article….this is a completely different effect.

12 minutes ago | parent | next [-]
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NetMageSCW 4 hours ago | parent | prev [-]

Tough behind a paywall.

nmstoker 2 hours ago | parent | prev | next [-]

And the Mig-29 too but according to the reply that's different

dathinab 7 hours ago | parent | prev | next [-]

yep

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 6 hours ago | parent | prev | next [-]

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aaron695 4 hours ago | parent | prev [-]

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