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Old 04-23-2007, 09:15 PM   #1
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Aerodynamic grooves/ridges?

I don't have the money or time to do this, but I was thinking about something. Perhaps to make a car more aerodynamic, instead of smoothing things out, rough them up a little?

In a way. Same principle as golf balls with the dimples, or rather, sharks.

Put ridges along the length of the car. Just short little things, but somehow texture the car to have small v shaped grooves following the flow of air. Should break up any surface eddies, and allow the air to flow much more smoothly over the car.

Anybody done this? Or anybody think this sort of thing would do any good? Anybody want to try this?
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Old 04-23-2007, 09:23 PM   #2
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From all I've read, this wouldn't make much difference. The dimples on golf balls work well for ... golf balls. Big macroscopic things like cars and airplanes are governed more by overall shape than surface.... that said, however, there are applications along these lines (vortex generators) but any difference they would make would be .... let me re-phrase... you'd need a high degree of measurment precision to even know if they MIGHT work in your particular case and then more analysis to attempt to find a way to use them effectively.... ie, I wouldn't bother with this approach without a wind tunnel unless I liked to run poor experiments and draw poorer conclusions from the variations due to experiment margins of error ;-)
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Old 04-24-2007, 03:28 AM   #3
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Anyone know the speed of a golf ball traveling down range? This gets me thinking about air tabs again.
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Old 04-24-2007, 05:29 AM   #4
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it's an interesting idea. i've seen sites mentioning ridges/grooves used on airplanes to prevent flow sepparation. it mentioned these could reduce overall drag by 6%. also the scales of most sharks where found to have small grooves in them wich made small streamwise vortices preventing flow sepparation

from what i know about the golfball dimples they also serve to prevent boundry layer separation.
personally i have stuck some small rubber cones at the back of my roofline where i want the air to follow the curve of the window. i have no real proof they actually work but they don't stand in the way of my FE improving so i think they help i'm planning on testing them further.

problem with ribs is that they only work when aligned with the airflow. sidewinds and frequent chancing of direction of a car might make things difficult
sources:
http://www.aerodyn.org/Drag/riblets.html
http://www.bio.davidson.edu/Courses/...0Reduction.htm
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Old 04-24-2007, 06:23 AM   #5
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Quote:
Originally Posted by JanGeo View Post
Anyone know the speed of a golf ball traveling down range? This gets me thinking about air tabs again.
Something like 150 mph would be a decent ballpark number, I think. And it spins at up to 8000 rpm in some circumstances, but that is more likely on higher numbered irons, where the velocity would be smaller.
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Old 04-24-2007, 11:14 AM   #6
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At those speeds the golf ball dimples would have some effect - I know they added them to generate more lift and increase range even when hit with a driver. I don't think dimples will have much effect at out car speeds when the real idea is to go slower anyway. They have added dimples on the motorcycle helmits on the rear half and top.
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Old 04-24-2007, 05:35 PM   #7
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I think it was BMW... But they advertised "dimpled panels" on it's undercarriage.... To keep noise down... But noise means air is doing something you don't want it to

Look at a whale fin - that's a remarkable shape... They suspect the bumps and other oddities help with it's fluid dynamic shape. Some of the newer/radical rowing/sculling paddles mimic the irregular shape too

------
Asides from dimples, the surface of a tennis ball does the exact same thing that golf ball dimples do So perhaps we should be covering our cars with a soft textile The goal is to energize the boundary layer - how you do that (dimples, fuzz, sand paper, etc.) doesn't matter too much.
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Old 04-24-2007, 07:06 PM   #8
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Yeah, either a BMW or Lexus had the dimpled under-panels.
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Old 04-24-2007, 08:26 PM   #9
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the vehicle that used to be the corban sparrow, I think it's now the NMG, has dimples on the trailing edges of fenders, and the body, and it makes sense to a point, they cause turbulance on a gulf ball to creat a buffer to cut down on drage, air tabs work in a simaler way to stir up the air, I was told you could do a simaler thing with a fake christmas tree sticking out the rear of your car.
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Old 04-25-2007, 02:31 AM   #10
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Or just don't wash your car and let it get all dirty and fuzzy . . . I don't know about fuzzy - that tennis ball slows down pretty fast after being served. Is that the dumb and dumber car?
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