Ribblets
 

I am looking for anyone who acutally knows what these are. Used on the Stars and Stripes hull. as well as the intakes of many NASCAR engines these little ribs or pockets like on a golf ball increase the flow of cylinder heads. The math is VERY high powered. I am looking for someone who acutally understands the math. I am an engineer with post grad degrees, who just wants to go faster.

I know just a little. I believe the ribblets are a passive method to keep the boundary layer from separating from the hull of the ship or wall of the duct (intake manifold). Keeping the boundary layer attached reduces the pressure differential (due to movement or fluid flow) along the shape or duct. There are active ways of doing keeping the boundary layer attached such as perforating the hull or duct with small holes or slits and pumping (sucking) on the boundary layer to keep it attached. This has been done on some experimental aircraft. I suspect the yachting competion rules disallow such active systems and perhaps so does NASCAR hence the passive measures. I seem to recall that the Navier-Stokes equations for these situations have never been solved at least in closed form. The commercial fluid flow analysis programs CFX/CFD may be able to numerically solve the equations for a given geometry. I have a colleague at work who likely knows more and a University contact who is expert in this area. I'll see if they can suggest some papers in the literature that can inform you further. Cheers, Jim

TerbaTrol says the boundary layer is an issue w/fender oil cooler design.. their inner tubes are finned to spin and agitate the oil. They claim a big increase in cooling efficency. I have an old brochure......... Ron

Jack, I have read in a book or publication some info on riblets. Cant for the life of me remember where I read it though. Race Car Engineering perhaps?

From my limited knowledge of aero aides, Im wondering how practical these would be? Ive seen the dark side of 200 in a 935 replica, and my own car MAY see 145 given the right conditions, ( my car is geared for about 145 at redline).


My recollection is that they keep the boundary layer attached, Its a neat idea to pursue, But how much difference will they make at a club racer level? Given the restraints of some of the tracks we run on (LRP not so fast), and (Watkins Glen balls out fast) Aero aides are the hardest variable to tune on our cars.

Ive seen some pics you posted in your other posts, is that your shop? Its quite impressive.

BMW tuner Metric Mechanic have something along similar lines. To be honest, I sort of figured it was marketing bunk...

They call it "Surface Turbulence"

http://www.metricmechanic.com/pg27.htm
http://www.metricmechanic.com/pg28.htm
http://www.metricmechanic.com/picshop3.htm

Oops.... are you talking about aero aids for handling, or aero aids for maintaining intake charge velocity?

Im sure the math is the same.. scale is different..

Its for intake runners and ports. Nascar is using it to make a few extra ponys, but all very hush hush, ie no one will show exactly what they are doing. I have seen some dimpling in aftermarket heads but I suspect that they do not have a clue on what really works as it is very very difficult to answer the question with exactly what you should do to your head. I talket to 3M, the company that made the skin for the Stars and Stripes. Its a plastic film with what looks like record grooves in it, much as the same thing that a Shark has on its body. Additional information is NOT forthcoming.

From what I do know about similar stuff, ie related to microwaves and filters, is that it would require specific spacings, groove depths, and would only work over a range of intake velocitys. To answer the same question in my field requires the knowledge that only a couple of people in the world have at their disposal. I suspect the same is true of fluids. I keep trying and someday I will run into one of them.

There are stories of people spending millions on a golf ball design, I suspect that is folklore, but I do suspect that some have spent big bucks trying to improve the air flow. I do not think the same answer for golf balls would apply to intakes so I think the dimpling in aftermarket heads is just blind dumb marketing hype and not real science. It is clear to me that the velocity would be a narrow range if a uniform array of dimples were used. I suspect the range would be so narrow as to be impractical for any use in auto racing.

didja ever notice on the top of airplane wings, those little tabs that run parallel to the planes direction... Called turbulator strips. Main function is to create a small wave over the surface to break up the boundary layer. Helps speed and prevents stalling. Used 'em on my model planes to a degree.

Same principal I think.

I always thought that the F1 cars would some day add dimpling ala golf balls to the bottom of their cars...

Now it is coming back, The reminder about the americas cup yacht cleared away some cob webs. I read an article that mentioned the 3m material that was used on the hull, and comparisons to sharks skin were made. It may have been in Scientific American, or even a boating magazine, or Popular Science?

The article touched on the theory, obviously no calculations or derivations were published. I got the idea the skin or riblets were similar to NACA ducts.

Unless this info has a high security level ( the gov uses the stuff for something) you may be able to find white papers that show calculations etc..

You may want to try
here for some leads.

This stuff and technology that makes it must be incredibly expensive, perhaps out of the realm of a club racer?