Golf Ball Dimples on F1

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Mr.Conte
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Super Cavitation Kinda

Postby Mr.Conte »

If anyone has access to some CFD tools; (yeah right)
I'd like to see the effect of a typical smooth surface eg. F1 body work vs. the same body work only fabricated with many small grooves running length wise with the flow of air.
I believe this might show a reduced surface area to the oncoming flow of air.
If so, this would allow the device / F1 car to slip through the air much cleaner resulting in faster trap speeds with the same amount of downforce as the non grooved bodywork.
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EyesInTheDrk
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Re: Super Cavitation Kinda

Postby EyesInTheDrk »

it would be exactly the opposite. you would increase surface area and drag.
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Re: Super Cavitation Kinda

Postby Mr.Conte »

I would like to measure the air pressure inside the groove vs the outside or on top of the high area.
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Re: Super Cavitation Kinda

Postby What's Burning? »

EyesInTheDrk wrote:it would be exactly the opposite. you would increase surface area and drag.


Not so sure about that, golf balls have dimples just for that reason however the golf ball spins through the air unlike the surface of an F1 car.

I think though if it would have been of some benefit we would have seen it on airplanes already.
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Re: Super Cavitation Kinda

Postby What's Burning? »

The dimples, paradoxically, do increase drag slightly. But they also increase "Magnus lift", that peculiar lifting force experienced by rotating bodies travelling through a medium. Magnus lift is present because a driven golf ball has backspin. The same Magnus effect can cause a ball to hook or slice if it has sideways spin.

Contrary to simple ideas of trajectories in a vacuum, golf balls do not travel in inverted parabolas. They follow an "impetus trajectory":

* *
* *
(golfer) * *
* * <-- trajectory
\O/ * *
| * *
-/ \-T---------------------------------------------------------------ground

This is because of the combination of drag (which reduces horizontal speed late in the trajectory) and Magnus lift (which supports the ball during the initial part of the trajectory, making it relatively straight). The trajectory can even curve upwards at first, depending on conditions! Here we see a golf ball in flight, with some relevant vectors:

F(Magnus)
^
|
F(drag) <--- O -------> V
\
\----> (sense of rotation)

A golf ball leaves the tee with a speed of about 70 m/s and a backspin of at least 50 rev/s. The Magnus force can be thought of as due to the relative drag on the air on the top and bottom portions of the golf ball: the top portion is moving slower relative to the air around it, so there is less drag on the air that goes over the ball. The boundary layer is relatively thin, and air in the not-too-near region moves rapidly relative to the ball. The bottom portion moves fast relative to the air around it; there is more drag on the air passing by the bottom, and the boundary (turbulent) layer is relatively thick; air in the not-too-near region moves more slowly relative to the ball. The Bernoulli force produces lift. (Alternatively, one could say that "the flow lines past the ball are displaced down, so the ball is pushed up.")

A difficulty comes near the transition region between laminar flow and turbulent flow. At low speeds, the flow around the ball is laminar. As speed is increased, the bottom part tends to go turbulent first. But turbulent flow can follow a surface much more easily than laminar flow.

As a result, the laminar flow lines around the top break away from the surface sooner than otherwise, and there is a net upward displacement of the flow lines. The Magnus lift becomes negative.

The dimples aid the rapid formation of a turbulent boundary layer around the golf ball in flight, giving more lift. Without them the ball would travel in more of a parabolic trajectory, hitting the ground sooner (and not coming straight down). This was discovered by accident in the early days of golf when golfers noticed that old roughened golf balls went farther.

Despite the drag, a dimpled golf ball can even go farther in air than it would in vacuum given the same initial velocity and low angle. However, a golf ball shot at 45° and 70 m/s in vacuum would go 500 metres to the first bounce, which exceeds all records.
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Re: Super Cavitation Kinda

Postby Fred_C_Dobbs »

The dimples on a golf ball serve as vortex generators. Most aeroplanes use vortex generators as well except theirs protrude outwardly from the wing. In some locations on the airframe, they reduce the stalling speed. In others they increase the effectiveness of control surfaces by bending dodgy airflow closer to the fuselage. Both work to accomplish the same aerodynamic effect but the bonding of the external vanes is cheaper than dimpling would be, plus it causes less compromise of structural integrity.

Dimples occasionally have seen use in bicycle racing, usually on the helmet but sometimes on the headtube and other parts of the bicycle itself.

Jan Ullrich in a dimpled time trial helmet in the 2003 Tour de France:

Image

Bicyclist prefer not to be subject to the Magnus effect (although Jan might have been when he took a tumble outside Nantes later that same year) but wind tunnel tests show the dimples' net effect is to reduce drag.

Vortex generators on the upper contour of the wing of a Beech Bonanza:

Image

If you'll look the next time you fly commercially, you'll see the same thing scattered up and down the wing of the jet, particularly forward of the ailerons.

Concerning using grooves in the body, as you noted, What's Burning?, no one makes more stringent usage of the principles of aerodynamics than the aeronautics industry. If these grooves had any positive effect, it's almost a certainty you'd see them on the aeroplanes built by EADS and Boeing.
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Re: Super Cavitation Kinda

Postby f1ea »

Fred_C_Dobbs wrote:The dimples on a golf ball serve as vortex generators. Most aeroplanes use vortex generators as well except theirs protrude outwardly from the wing.


:yes:
The vortex increases the size of the boundary layer, and thus the 'effective' cross section of the flow is reduced, and the flow velocity increases (that means the pressure drops). Although there is actually less friction along the boundary layer/air flow suface versus the car surface/air flow section. But we'd have to look into the flow in question to know if the higher velocity ends up producing more friction losses than the original surface at lower velocity (because losses are dependent on the velocity squared). Maybe (very likely) yes, but maybe no. I guess they are willing to compromise some drag for the extra pressure gradient.

If the F1 car bottoms were dimpled... they'd have a lot more downforce. Some time ago we talked about this....
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Re: Super Cavitation Kinda

Postby stonemonkey »

Mythbusters looked into the golf ball dimples on cars.

[youtube]8DAUcPlz_5k&feature=related[/youtube]

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Re: Super Cavitation Kinda

Postby darwin dali »

:yes::thumbup:
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Re: Super Cavitation Kinda

Postby What's Burning? »

I want an F1 Mythbusters, if we all write the suggestion in....?
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Re: Super Cavitation Kinda

Postby f1ea »

stonemonkey wrote:Mythbusters looked into the golf ball dimples on cars.


really cool. But in a F1 unless it had a dimpled bottom as well, then the dimpled car would have less downforce.
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Re: Super Cavitation Kinda

Postby What's Burning? »

f1ea wrote:dimpled bottom


There's a joke in there.
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Re: Super Cavitation Kinda

Postby Mr.Conte »

What's Burning? wrote:
f1ea wrote:dimpled bottom


There's a joke in there.

I bet you that Alonso's bottom is full of dimples to be chasing the RBR team around when he sits in a mighty Ferrari. :rofl:
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Re: Super Cavitation Kinda

Postby nish2280 »

I dont get it, why do dimpled bottoms benefit the car? if anything they are detrimental, they create vortices which is turbulent and non-uniform airflow which would as a result create more drag.

A car would require smooth low pressure underneath rather than the high-pressure the vorteces would create. Turbulent air--> air particle collisions with body+ground --P=F/A--> high pressure-->higher ride height
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Golf Ball Dimples on F1

Postby CorkSoaker »

Are golf ball like dimples allowed on an F1 car? The dimple technology ought to allow for slightly greater top speed aerodynamically, less fuel consumption due to better mileage and associated better cornering speed with less fuel carried.