Fapout

Interesting.

Click here.

Its the full episode, the test is around the 40 min mark. Turning a car into a dimpled golf ball to raise fuel economy just as a golf ball flies easier...

I would post the results but I don't want to spoil the fun of busting a myth.

Olegator

yeah, I remember watching this

dammitjim

Cool video.

Does this mean the golf ball kit will give a drag limited car a higher top speed?

beanseff

honestly, from an engineering standpoint i don't understand how dimples would make for better aerodynamics, you would think it would create more drag, but evidently it's the exact opposite

Fapout

maybe it creates turbulence in each dimple causing more fluid aerodynamics... anybody really smart care to chime in or at least google that?

Bobert

I think it might be because there is less surface area for the air rushing over the body to "grab onto," if you know what I'm saying.

Kremlin

I don't understand how this could work.. the dimples on the golf ball rely on the fact that the golf ball is spinning.

Also I wonder how they know they accelerated EXACTLY the same every time?

Mr.E.G.

It has to do with the boundary layer that surrounds a body moving through a fluid. To understand this, don't think of a fluid as loose collection of molecules. Instead, think of it as layers of carefully organized molecules; one layer atop another kind of like layers of skin or of the earth's crust.

Think of oil or some other viscous fluid to make it easier to understand.

As we are all aware, if oil flows over an object, the part of the oil flow that touches the body will "stick" to the body. The layer of oil directly atop that layer will "stick" to it. The layer above that one will "stick" to the one below, so on and so forth.

So if you were looking at it from the side, you would see that the fluid immediately touching the object sticks to it and slows down dramatically, however, as you go further and further from the surface, the layers are less affected by what is going on on the surface of the body.

This area of affected layers, is referred to as the boundary layer. The further the boundary layer extends off of the body, the more of an impact it will have on the air around the body.

Another feature of the boundary layer is that it will compound over a flat surface. Just think of honey flowing down the side of the jar. At the top of jar the honey will be relatively thin but the layer of honey will build up toward the bottom. Naturally, the flow of honey is caused by gravity in that example, but if the jar were flying through the air, it would have the same effect.

The dimples n the golf ball break up the boundary layer by creating deliberately induced and localized turbulence which "stirs up" the air in that region and keeps the boundary layer from being quite so thick. As a result, the air immediately touching the body will have less of an effect on the air around it (since the boundary layer does not extend to far outward), less stickiness if you will, and that will result in a lower amount of drag. Less drag means that the ball will fly further with the same amount of applied force. Of in the context of a car, it will go faster with a given force or require less force (less power and therefore less fuel) to obtain a given speed.

Please note that the above explanation is watered down quite a bit but I can go into more detail if anyone cares.

Mr.E.G.

You are on the right track, but technically there is more surface area.

Mr.E.G.

The main thing to consider is that the largest contributor aerodynamic efficiency is the overall shape. A ball shape is far from the least draggy shape out there, but it as also not terribly bad. Modifications such as the dimples are really just a matter fine tuning and should be looked at as the major source of the issue.