Theory of the Golf Ball Dimples

[RandomFact314]

I was just watching a video on Youtube where these guys got a hold of a golf ball dimpled skate board that was supposed to flip faster so they could do better tricks, they were not sure if the golf ball dimple design really helped. I remember thinking back in the day about cars with this design but never really knew what the science of it was so I looked it up on Youtube.

This is a great little video explaining when it does, and when it doesn't help to have this design.... Given what he says, do we still think it's not worth adding to our cars? Im sure some cars would benefit more that others?

https://www.youtube.com/watch?v=ZXpZy_A7mMk

[LittleBlackDuck]

There was a mythbusters episode that looked at dimpled car bodywork to reduce the boundary layer drag, and as far as I recall the concept was busted.

Simon

[RedDevil]

Dimples work on golf balls because they influence the way the air adheres to the ball at the back.
The ball needs to be round, so there is nothing that can be done shape wise to reduce the drag; also the ball can rotate in any way, so any measures need to reduce drag need to be omnidirectional.
Dimples do that.

Cars do not need to be perfectly spherical and they move primarily in one direction.
That is why cars do not have the same problem as golf balls; the necessity to use dimples has been designed out, and indeed cars have a way lower Cd than golf balls, even though the latter have dimples.

There is no need for dimples on a car, just as there is no need to hit it with a club

Looking for more videos on golf ball dimples, I was impressed by this one:

https://www.youtube.com/watch?v=zZsvpw-JOO0

[LittleBlackDuck]

Originally Posted by RedDevil

.There is no need for dimples on a car, just as there is no need to hit it with a club

I can remember a few times when hitting the car with an object similar to a golf club would have been beneficial...

Simon

[RandomFact314]

Originally Posted by LittleBlackDuck

I can remember a few times when hitting the car with an object similar to a golf club would have been beneficial...

Simon

I can remember a few times when hitting one of my car's with a crane would have been beneficial... I've had too many garbage cars

[LittleBlackDuck]

Agreed. I have also had way too many close calls with idiots or wildlife out on the roads to stuff around with old clunkers. I now insist on having cars with all of the possible safety features. Only a couple of days ago my wife was saved by the active cruise control on the RX450h. Another driver decided that it was too hard to wait till a car had parked and just drove on the wrong side of the road. The active cruise initiated braking before my wife realized the threat and stopped the car short.

Cheers
Simon

[Xist]

This is the first civilized dimple discussion I have seen in a long time. I usually run for the pitchforks and torches. Here is Aerohead's response to Mythbusters. From what I have read here, dimples are weak vortex generators, but VGs only work in one direction, and VGs are called "band-aids for bad aero." If you properly shape a car, VGs, and especially golf ball dimples, would not help, and someone pointed out in the thread I linked that they put dimples all over the car, while it only had a chance of helping where there would be detached flow, like the rear window.
There have been many discussions on golfball dimples on here, with people explaining the Reynolds Number states dimples will not help on an object larger than a golfball, round, and spinning.

[freebeard]

The golf ball flies out of ground effect. Skateboards and cars don't. QED

LittleBlackDuck -- Does the LX450h have an electric rear axle or a driveshaft? The motor for my someday EV conversion is from the LX400h.

[ChazInMT]

I just refer folks to This Article on Hot Rod dot Com from a guy who is as close to an aerodynamic guru as we'll ever know. Towards the bottom he states under the caption

"Aero Stuff That Doesn’t Really Matter
In addition to our list of five tricks that almost always work, here are some things A2 customers might want to try that are really a waste of time.":

"Golf-ball dimples: They do not work on cars, regardless of the scale of the dimples, unless your car is a 1.68-inch-diameter sphere spinning through the air with no ground plane."

So, Boom. Fantasize about dimples working all you want. Greater minds than ours have said "Fuggedda Bout It". 9 Years ago no less.

[MobilOne]

What is the ground effect referred to above?