This article was originally published in the Nov./Dec. 2013 issue of Inside Triathlon magazine.
Figuring out whether or not you successfully shaved weight off your bike is simple. Understanding aerodynamic impact, however, is much more difficult. Knowing how a shape reduces or increases wind resistance is a powerful tool for tri gear designers, and these three types of aerodynamic testing — both new and well established — are helping to provide those answers.
Purpose: Detailed attribution of performance
Testing two different helmets, for example, on a dummy in a wind tunnel can reveal which one is faster but cannot determine why one prevails over the other. Computational fluid dynamics (CFD) software, which acts like a digital wind tunnel, simulates air passing over an object and visually depicts airflow. This allows a designer to identify parts of a product that minimize aero drag and those that do not. CFD also helps an engineer get the most out of wind tunnel tests.
“CFD allows us to go through hundreds of design iterations in a relatively short amount of time,” says Felt engineer Anton Petrov. “In the end, we utilize the wind tunnel much more effectively because we do our homework ahead of time.”
Purpose: Reliable, repeatable drag data
Mount an object to a horizontally oriented scale, stick it in a stream of consistently flowing air and measure the force pushing against that object. This 25-word explanation doesn’t do justice to the complexity of wind tunnels, but it’s the basic concept of how they work.
For decades, wind tunnels have been used to improve gear design and rider position. If you have even a passing interest in triathlon equipment, probably none of this is news to you. Even today, these seemingly arcane contraptions play a critical (and very effective) role in aero testing. The best CFD simulations have error, and they take a tremendous amount of time and money to set up. From Zipp to Specialized to Hed to Cervélo and more, nearly all the companies that do genuine aerodynamic development use wind tunnels to test products because they’re an effective way to reliably measure how a product will perform in the real world.
Measurement While Riding
Purpose: Measure drag while riding on the road
Wind tunnels accurately replicate cycling and produce reliable, repeatable results, but a few minor factors still differentiate real-world cycling in subtle ways. First and most important is wind variability. Obstacles on the side of the road, other riders and terrain all impact the speed and direction of wind actually experienced by the rider — and that’s when the wind itself is completely consistent.
Mavic uses a wind vane that can be mounted to bicycles to measure the wind conditions a cyclist truly faced in a ride, and Specialized takes this process even one step further. The company constructed a system that measures wind and also is capable of determining drag on the road. Specialized uses this tool to refine athlete positions and work on equipment. Ero Sports uses a system capable of measuring the wind drag created by a rider and his bike while circling a velodrome, and many professional triathletes are already using it to refine their position and equipment choices.