Hexagonal Dimples as a way to improve aerodynamics

[trebuchet03]

Originally Posted by Cd

How does dimpling help on a golf ball if the ball is spinning constantly ?

Same as before, just on one side (the low pressure side)

Other things to note.....
The seam on a baseball, create a similar effect as golf ball dimples. There's a reason why baseballs are changed frequently and attempts to rough them up is banned

The slightly raised seam on a cricket ball - it too

Tennis balls... they're fuzzy... Another aero changing feature

The texture of a football

Panels on a soccer ball

Jai Alai ball - arguably the fastet/most lethal ball...

etc. etc. etc.

That's interesting and all.... But only applicable for similar Reynolds numbers

Dimpled underpans would have another non-aero reason for being dimpled...
NVH reduction - Noise, Vibration, and Harshness.

Look at where dimples are being applied for aero - super tight curvature objects that just happen to spin pretty damn fast. A flat, or even mostly flat panel is not going to be directly applicable.


Now, some cattle chew....


Zipp offers dimpled wheel sets for cyclists... again, fast spinning, tight radii, small length..... And yes, their claim is aero - not strength

[aerohead]

Originally Posted by Palionu

Yes, I agree, doing a homer simpson on your car is not a good idea, especially around those flat areas. I remember one luxury car manufacturer has a dimpled bodypan that they said increases their fuel efficiency for the same model car by a certain % but that could have been a pitch. I like the idea of adding turbolators to the trailing edges and my front bumper = EEW so I might install some dimpling on the outside edges after i do the front grill delete. I like the idea of adding those silicone bumpies on the mirrors though. I lack the money to invest in a $200+ mirror delete (the cost is in the cameras).

For the rear area I read on a Smart Four-Two forum that aside from them complaining that their not so 'smart' cars aerodynamics were inhibiting his cars potential he went to a canadian semi-truck site and invested in some AirTabs. He installed 8 at the cost of $2.75 each and went from 34mpg to 42mpg... maybe another vortex generator option? Sorry, lost the link =/

Another site with various color options is here

I think I saw that ad.I believe the "dimpling" has to do with the "sandwiching"Lexus does to the sheetmetal to bond sound-deadener material,and also move the resonant frequency of the panel outside the range of vibrations (or their harmonic counterparts),so the panel won't hum.------------ The dimples form inverted pools of stagnant air,which the surrounding flow field merely passes over with virtually no aerodynamic penalty.Clever!

[aerohead]

Originally Posted by Cd

How does dimpling help on a golf ball if the ball is spinning constantly ?

As far as dimples on automobiles, I notice that Lexus did a famous job of dimpling the LS430 underside, and to my surprise VW is still using dimpling on the undersides of their cars . There must be something to it, otherwise they wouldn't bother ( Lexus used the dimples as a PR stunt, and this may have been the actual reasoning behing the dimples, but why then is VW using them if they don't really work ? )

Evidently,the spinning is of little consequence, as the revolving "face" always presents the dimples to the "oncoming" flow.At a clubhead departure velocity of 110-mph,Reynold's Number goes supercritical immediately,and drag coefficient drops from 0.47 to 0.10.----------------------- As mentioned elsewhere,the floor of the Lexus is a sandwich of 2-layers of sheet steel,encapsulating a membrane of acoustic deadener.The presence of the dimples further alters the resonant frequency of the floor,along with any harmonics which might occur within the range of the engine/driveline vibration.

[nucleus]

Time to resurrect this thread...

VIDEO: Mythbusters test golf ball-like dimpling effect on fuel economy (*Spoiler Alert!*) — Autoblog

[wdb]

Originally Posted by nucleus

Time to resurrect this thread...

VIDEO: Mythbusters test golf ball-like dimpling effect on fuel economy (*Spoiler Alert!*) — Autoblog

Amazing. If there is any fault in their methodology it is that they dumped all the dimples in the back seat, thereby raising the nose of the car relative to the undimpled pose. But that ain't much, and I would be surprised if it would account for an 11% difference in FE.

[trebuchet03]

Originally Posted by nucleus

Time to resurrect this thread...

VIDEO: Mythbusters test golf ball-like dimpling effect on fuel economy (*Spoiler Alert!*) — Autoblog

I am thoroughly impressed - another example of why aerodynamic interactions are phenomena (that is, you can't use intuition to predict!). My prejudices were wrong, and I'm quite intrigued

I haven't watched the episode (yet) - but how did they scale up the dimples? By relative size to a golf ball? Or relative velocity? Or just a guess?

Amazing. If there is any fault in their methodology it is that they dumped all the dimples in the back seat, thereby raising the nose of the car relative to the undimpled pose. But that ain't much, and I would be surprised if it would account for an 11% difference in FE.

Even if they pitched up a little, that would have been working against them... and 11% difference sounds, potentially, outside the scope of reasonable error


-----
Yes, impressed enough to un-silence myself I graduated school this past spring, have been really busy, visited 30 cities on the all you can jet pass, and am now doing contact work/working super hard for a start-up in San Francisco to meet fast approaching deadlines....

[Hatchtastic]

that was one of the most beautiful things I have ever seen...

[JackMcCornack]

Originally Posted by hypermiler01

The effect would be not even remotely close to the benefits of adding a Kamm back or boat tail.

That's my opinion as well, but by golly the dimples on the roof may well be simulating a crude Kammback. it looks to me like the rear window area is about the worst angle it could be for drag (if I remember my Hucho, 30 degrees is worst, 15 best...YMMV) and the dimples near the back of the roof are probably detaching airflow over the rear window. A little spoiler up there would do it better I'd think, but anything would help.

[wdb]

Watch the date stamps, this thread is a back-from-the-dead special.

[dwtaylorpdx]

Dimples make sheet metal more rigid as well, more strength less weight under the right conditions.

Dave