When packs of drivers jockey for position on the speedway at Sunday's Indianapolis 500, a select group of engineers will be thinking, not about engines and tires, but about the effects of laminar and turbulent airflow.
"It's one thing when you're riding around the track and there's no air disturbance," Mark Johnson, general manager of KV Racing Technology, told us. "But when you're in a three- or four-car pack driving through disturbed air, it's another matter. That's why the wind tunnel simulation is so important."
Indy's engineers spend hundreds of hours testing cars in wind tunnels. Along with on-track testing, KV Racing employs a "rolling road" at a wind tunnel to build an "aero map" of its vehicles. The rolling road, operated by Wind Shear Inc., measures 10.5 feet wide and 29.5 feet long. Its continuously turning steel belt can accelerate from 0 to 180mph in less than a minute and incorporates a measurement system that monitors the aerodynamic downforce under each tire.
Indy cars can use aerodynamic downforce to ride lower and get a better grip on the road. (Source: Littelfuse)
"Going to the wind tunnel is critical to our understanding," Johnson said. "The engineers learn what happens when they make a change on the rear or front of the car, and they find out what they have to do in order to make all the changes work in concert with each another."
Given the new rules at Indy, those changes won't be big, but they can still make the difference between victory and defeat. One of the key components not constrained by the rules is the wicker -- a little piece of angle iron on the car's front and rear wings. The wicker, measuring anywhere from one-sixteenth to one-half of an inch in cross-section, can run the full width of a wing (about 18 inches across). By altering the size and angle of the wickers, engineers can significantly change the aerodynamics of their vehicles. To find out how much change they've wrought, they bring the vehicles to the wind tunnel or to the actual track and take measurements.
At a track in Texas, for example, KV recently experimented with wickers to provide more aerodynamic downforce for a rookie driver. Starting with a flat rear wing and varying the size of the wickers on the front up to three-eighths of an inch and then down to one-fourth of an inch, they found they could produce amazing amounts of downforce. "We got to where he could drive around the track and never lift the throttle for five or six laps at a top speed of 205 miles per hour," Johnson said. "After he got more comfortable, we took a little bit of the wicker off."
Such adjustments are commonplace for Indy race teams, Johnson said. Through trial and error, they learn how to use aerodynamics to make their cars ride high or low, increasing or decreasing drag and thereby tweaking the downforce. "You can get the car to ride closer to the ground, which increases your grip, or you can let it ride higher and faster. It's a very fine balancing act."
You can learn more about the Indy 500 at Littelfuse's Speed2Design site.
I agree that some of the aerodynamics improvements have made racing less exciting. However, I think technology has also made racing more exciting. I disagree a little bit with this article because it focuses so much on aerodynamics. There is so much more to racing. I am in awe that taking 1/2 pound of air out of the left front tire can really make that much of a difference in how the car drives. But it does. Absolutely awesome.
I agree. Going away from the human element would decrease crowd size as well as make things too automated. Part of the fun of racing is watching someone take a risk that a computer wouldn't take and succeed causing them to win the race.
In quite a few races the difference between winning and losing is knowing how much gas is left in the tank and often that is a little bit more than an educated guess. But not much more.
Steamlining, or reducing the airflow drag, is certainly the best way to get "free horsepower" for racecars. IT^ does get complex when there are multiple cars close together, though. Drafting is a bit different, it works for most cars on the road. We proved that back in 1967, using vacuum gauges to measure "effective engine load", which was a lot cheaper than an air tunnel or dynamometer. The problem with doing experiments on the local interstate is the way other folks get so upset at seeing two cars six inches apart. But it is safer than you might think, because if the front car slows quickly the second car catches up quickly and so the impact is quite small.
The number of blades on the big wind turbines is the result of a compromise that includes cost and weight, rather than being based just on maximum energy recovery. Otherwise they would have more blades.
Reducing the drag on "big trucks" is a very valuable effort because of the large number of them around. I am waiting for somebody to try air dams on the trailers and some sort of means to avoid the high-vacuum turbulence that I see behind the trailers. I have thought for some time that lowering the box three feet could do a lot to reduce the drag, but there are a lot of other considerations, it turns out. BUt I have seen a lowered tanker truck and it did look a lot more stable than the standard ones. IT would be very educational to hear what the research folks have come up with relative to steamlining trucks. After all, even a 1% reduction in fuel consumption would save a whole lot of money.
Well Jerry, Bill was a very highly respected engineer in the automotive industry working for Hudson, Packard and Ford. He held over 80 patents which I suspect is more than you ever will. Bill grew up as a farm boy in Western New York State and knew the difference between horsesense and horsedukie. And yes, they had an aermotor. And after a huge wind storm coming in off of Lake Erie when the rotor blew off, he learned about the tremendous power in the wind when he hoisted the baby back on the axle on a summer vacation from Michigan while studying with some preeminent engineers, some of whom you may have heard of.
Ever hear of the Packard Torsion Ride? Sir Clive Moulton was aware of his work and inspired by it as a young boy.
Bill was a classic American of that era, believe me he didn't lie ever. In fact he recorded the lift off of the Challenger and had it completely analysed within several days and sent NASA his analysis. He showed me the graphite streaks. It took them over a year of analysis to come to the same conclusion. And he knew who caused the disaster and began to worry about government agents. You know who caused the disaster don't you? His analysis of the crash of flight 255 revealed that he knew a lot more than the Judge.
Bill knew enough to stick with the problem until he solved it. That is why he was so very successful. Lie? Outrageous conclusion. If you look at the succession of articles in Popular Science you will notice that every time he added more blades the efficiency went up in the next article.
In your third paragraph You purport to have all the facts. You don't. Your mind is closed and dead. You mention sail boats. So you probably have heard of the spinnaker. Tell me about it. Does it operate on the same principle as the mainsail? If you say yes, we know that your education and experience has led you to some very erroneous conclusions which you hold as the precious truth. It's not and you are the one who is wrong.
Those 3 bladed fans try and fly in the wind. Bill's didn't. They resisted the wind. The greater the number of blades, the more energy he got.
So you are one of the flyers that he was so scornful 30 of years ago.
You are one of those, so convinced in your "truth" that you go down the same path over and over again hoping to see a huge change. You won't. Psychologists have a word for that.
So your words... lie, just plain wrong, "facts", isn't going to be, misinformed, vaporware, scam... are more than rash.
Show us how you determined your efficiency, show us that you understand the different physical principles of dealing with the wind, show us your calculations, and show us that you are open to other lines of logic and physics, othewise those words that you are trying to stick on a very noble enginer really apply to you.
The flyers have lost according to Buford. Did you miss that?
Yes Bil was either lying or just plain wrong. I design, build windgenerators among other things, presently doing 2 2kw designs for production.
And mine will hit 35-40% eff, not 20%
Facts are the best wind power collectors are 3 blade rotors like you see on most all cost effective WG's. As more blades are added they just interfer with the ones before it and add drag, lower tip speed needed to make real power. Basic physics, deal with it and stop making ill informed statement.
Do you know why there is a Belt's limit? Air flowing to a WG if too much energy is taken, the wind slows down in front of the WG rotor and goes around it instead.
I've done every type of WG including fast 20-30mph sailboats and physics holds well on all of them. Sadly means any WG with more than 5 blades just isn't going to be eff, cost effective.
If you think Bill's WG is so good build them and make a fortune. Until you build and prove your points it's just misinformed vaporware or just a plain scam.
Thanks, bonjengr. It's surprising how important those wickers have become. IndyCar's rules are so confining that teams now spend thousands of hours working on details -- such as wickers -- to distinguish themselves.
Charles—Fascinating article!OK, the first time I have heard the word "wickers" in my life—first time.You mention in your write -up that KV spends considerable time with trial and error before settling upon a suitable design that gives optimum performance.I recently published an article on the Sim Center located within the University of Tennessee at Chattanooga facilities.This center performs computational engineering analysis on air flow ( and other things )around the "big rigs"; eighteen wheelers fully loaded and going coast to coast.This is a remarkable technology and certainly one not existing when I was in engineering school.Maybe the folks at KV could gain additional insights and reduce the time tolaunch with this approach.Again—great article.
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