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The Torqued Wrench: Aero is everywhere

  • By Caley Fretz
  • Published Apr. 25, 2012
  • Updated Apr. 26, 2012 at 12:35 PM EDT
Wind tunnel testing yields solid aerodynamic data, but can't account for real-world variables

Three-pronged attack

With the benefits of aerodynamics now established, the task becomes one of innovation and advancement.

However, replicating and measuring the precise aerodynamic forces applied to a rider in the infinite number of situations in which he may find himself is impossible. Those who test aerodynamics must therefore make assumptions, selecting the situations they believe occur most frequently or simply endeavor to remove as many situational variables as possible. To that end, the best in the industry utilize any and all tools currently available to them.

The first is wind tunnel testing, by far the most ubiquitous. The second is real-world testing, performed under a wide variety of protocols. The last is computational fluid dynamics, or CFD, which uses exceptionally complex algorithms to model airflow over a given shape. Each has its strengths and weaknesses: situations in which it is highly valuable or completely useless.

Testing equipment

In general, CFD and wind tunnel testing are the most effective for testing equipment, which is relatively static. CFD is usually used in development, and then concepts are validated in the wind tunnel. You can thank CFD for the recent rise in ultra-stable wide wheels, as well as most aero road frames and all the best time trial frames. Manufacturers can test and re-test without the enormous expense associated with hours in a wind tunnel.

“We use the wind tunnel more on stuff: products and such,” said D’Aluisio. “The repeatability is there. We also do a lot of pure component testing, and that testing is almost impossible on the track.”

Wind tunnel testing is so popular because it provides a laboratory setting that can never be found on the road. “On the road, you can’t control changes in wind, changes in temperature, changes in body position, or changes in road surfaces,” says Robby Ketchell, aerodynamicist with Garmin-Barracuda. “But you can control all those in the tunnel.”

The tunnel isn’t perfect, though. While it can control a number of important variables, there are many more that are left out completely. Cyclists and their bikes are a system, and they reside within a much larger system that includes all those variables — like drafting and position changes — that the tunnel eliminates. There are thousands of inputs that can’t be replicated in a wind tunnel, and that make it an inexact method of determining real-world gains. It can get very close, but is not perfect.

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Caley Fretz

Caley Fretz

Tech Editor Caley Fretz came on board with VN in September 2010, and now splits his year between Boulder, Colorado and Annecy, France. Beyond his journalistic pursuits, he is a category 1 road, 'cross and track racer. He also holds a pro XC mountain bike license, though unlicensed racing is now more his style.

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