I was just thrown for a loop last night after watching this.

Will dimpling a car, much like a golf ball, make it travel better through the air?

All that I know of aerodynamics would tell me no. It will grossly increase drag. This is why every surface of a car built for racing is smooth right? I even thought that the matte finish on the Army NASCAR a year or two back was at a disadvantage.

These guys took it over the top though. They tested in a water tank and decided to go to full scale testing after they got better aqua dynamic results with the dimpled car.

Before the video, they tested the car's gas mileage without clay, then put nearly 900 pounds of clay on and tested again. The video pics up after they make dimples in the surface of the car and he's putting all the excess clay from the dimples back into the car to keep the weight consistent.

http://www.youtube.com/watch?v=BWWe8j3-Vs4&NR=1

I want some thoughts from others. I don't think something like this could be even remotely usable in sports like F1 with all the winglets guiding the air, but could this create some of the ugliest race cars we've ever seen in NASCAR, or GT racing?

Saw that episode some time ago. I honestly didn't believe it at first, but it really seems to work, although I'd like to see some more tests...

But yeah, don't see any cars, commercial nor race, see use this.

the principle is very useable in sports and aeroplanes as most airplanes user boundary layer energisers on their wings and in their flap design similar to how all f1 cars use muliple element wings to keep the boundary layer at high flow and attached

It's really not all that complex of a principle, not sure why someone would immediately discard the idea.

You may gain on fuel efficiency and reduced drag but the counter effect would be reduced downforce and obviously the aesthetic argument. It could be applied to the marine sector though?

they tried it on a plane, didn't work properly.

I thought the dimples on a golf ball made it fly further by increasing the lift as it spins rather than lessening air resistance?

Quote from Crashgate3 :

I thought the dimples on a golf ball made it fly further by increasing the lift as it spins rather than lessening air resistance?

The dimples act to rough up the boundary layer of air flowing over the golf ball. A smooth ball will have a smooth (laminar) flow of air over it until some point on the backside when that flow detaches from the surface of the ball. What you are left with then is a space behind the ball of low pressure before the air comes back together. This area of low pressure acts to slow the ball as it is literally sucking the ball back. There is increased drag as the air did not come together cleanly. This is the reason anything that is designed to cut through fluids (planes, ships, etc) taper to a point. To allow a smooth reattachment of the air flow with minimal drag and no low-pressure suction zone.

A golf ball obviously cannot be tapered to a point, however you can cheat by adding dimples. Dimples "rough up" the laminar flow over the surface of the ball, turning it turbulent. A turbulent layer of air has more energy, and is able to hang onto the surface of the ball longer. This allows it to stay attached a little bit longer as it travels along the backside of the ball. This means there will be a smaller low-pressure zone behind the ball, and less drag, allowing it to fly a little bit further.

Your explanation of spin doesn't really work, because as far as I know, a gold ball does not only spin one way in the air. The ball will exhibit increased lift on whichever side is rotating in the direction of travel, as the relative airspeed over that surface would be the ball's speed PLUS the rotational speed, which would lead to less pressure than the opposite side. However, if the ball spins the wrong way, you suffer REDUCED lift. So unless you can control the way in which the ball rotates, there is no way to influence lift in this way.

Quote from Scott Mckenzie :

You may gain on fuel efficiency and reduced drag but the counter effect would be reduced downforce and obviously the aesthetic argument.

I don't see why there would be less downforce if this was applied to a car. The effects of these dimples are only to allow the flow to remain attached to the surface of the vehicle. I don't believe it would have much of an effect on downforce. A dimpled wing on the back of a car will still be deflecting the air in the same way as a non-dimpled way. In fact, I would think it would be likely to increase downforce as it allows the air flow to stay attacked to the airfoil longer, allowing the air to flow better and increasing the efficiency of the wing. Not too sure about that though.

Quote from Stang70Fastback :

I don't see why there would be less downforce if this was applied to a car. The effects of these dimples are only to allow the flow to remain attached to the surface of the vehicle. I don't believe it would have much of an effect on downforce.

generally the method of generating downforce (or rather of how to decrease lift in "normal" cars) on cars (with the exception of anything ground effect related) is to do the exact opposite of filling the wake in eg by using spoilers at the trailing edge of the boot and thus the car
i think the general idea here is that when viewed from the side a car roughly resembles a wing profile (particularly obvious if you look at the 911 which is one of the worst lift generators out there) and to stop that profile from generating lift you want to keep the flow across the top from mixing with the flow across the (usually flat) bottom

I'm really surprised abut that result. Had a discussion over some beers with a mate some time ago where I had the idea to dimple the inside of your engine's intake manifold, but we where sure that only works on spherical objects

I'd actually read about the shark fact a while ago, and I wondered if it would work.

The video proves it does, but what effect will it have if the dimples on the car are much smaller, akin to a golf ball?

I'm surprised that none of the big manufactures have tried it, or atleast to my knowledge.

Quote from Shotglass :

generally the method of generating downforce (or rather of how to decrease lift in "normal" cars) on cars (with the exception of anything ground effect related) is to do the exact opposite of filling the wake in eg by using spoilers at the trailing edge of the boot and thus the car
i think the general idea here is that when viewed from the side a car roughly resembles a wing profile (particularly obvious if you look at the 911 which is one of the worst lift generators out there) and to stop that profile from generating lift you want to keep the flow across the top from mixing with the flow across the (usually flat) bottom

You're right. I wasn't really thinking. I guess it would have to be a trade-off. It always is a trade between downforce and drag.

I would never take anything from those guys as a fact, watching their show just makes me angry. If someone else does it in a controled environment, I'm interested, their way of testing a hypothesis is _always_ prone to having unintended side effects affecting the result.

My defenition of PopScience appies to them.
Popular Science- Science explained in a simplified way, so simplified that only disinformation remains.

Those guys are quite funny and tbh only reason I tune in is because of that dirty red head to whom which I want to carry out acts of extreme boldness!

¥evilgrin¥

Quote from ACCAkut :

I had the idea to dimple the inside of your engine's intake manifold

im guessing here but i wouldnt be surprised if the turbulent boundary layer generated by dimples would lead to a much less efficient intake stroke
almost certainly if the dimples arent part of the engines design

Quote from heson :

I would never take anything from those guys as a fact, watching their show just makes me angry. If someone else does it in a controled environment, I'm interested, their way of testing a hypothesis is _always_ prone to having unintended side effects affecting the result.

My defenition of PopScience appies to them.
Popular Science- Science explained in a simplified way, so simplified that only disinformation remains.