Caltech Scientists Test Air Flow Over the 2010 World Cup Soccer Ball (w/ Video)

Jun 25, 2010
One of the main differences among soccer balls is how much the air flow follows the ball's surface. Turbulent air flow would hug the curvature of the ball, reducing drag. In this high-speed video of the Jabulani ball, however, Caltech scientists demonstrate that the air flow actually separates after about halfway across the ball.

(PhysOrg.com) -- The World Cup is in full swing, complete with an official new soccer ball named Jabulani, meaning "to celebrate" in Zulu. The players, however, aren't exactly celebrating. Instead, many of them are complaining that the ball's trajectory is too hard to predict, and that the ball itself is too hard to control, resulting in wayward passes, shots flying off target, and goalkeepers looking silly. So what exactly is it about the new ball that's provoking all the controversy?

To find out, Caltech engineers in the lab of Assistant Professor of Aeronautics Beverley McKeon put an official Jabulani through its paces in the Lucas Adaptive Wall . And what they found there may explain the seemingly unpredictable nature of the Jabulani.

To start with, the classic black and white soccer ball, stitched together from 32 panels of pentagons and hexagons, has deeper grooves. The Jabulani, which is made from only eight panels thermally bonded together, has more shallow grooves, as well as tiny raised patterns along its surface.

This video is not supported by your browser at this time.

Heavily textured surfaces can result in more turbulent air flow around a ball, which, McKeon explains, reduces drag at the speeds typical of a soccer ball kick and allows a ball to travel farther. (That's the reason golf balls have dimples, for all you putting aficionados out there.) As a soccer ball slows down after it's kicked in the air, the air flow around it changes from turbulent to smooth. It is likely that the details of this transition are different for the traditional than for the Jabulani, which from the point of view of a soccer player translates into a ball that's behaving unpredictably.

It's also possible that wind, spin, or other influences can have a stronger effect on the Jabulani's trajectory. As the ball hurtles through the air, the varying air flow around it can send it on unexpected paths, to the consternation of many soccer players.

Members of the media gather to cover the test. Credit: Jenny Somerville

Still, the Jabulani isn't so unpredictable that players can't learn to control it. "It seems like anytime the ball is changed, it takes a while for people to adapt," McKeon says. And from a fluid mechanics standpoint, the Jabulani's also pretty interesting. Studying the air flow around balls is a natural extension of McKeon's research, in which she and her colleagues study how surface roughness affects air flow, using spheres as test models. They're looking at how they can control air flow just by changing the texture of a surface. Their work has many applications in aircraft design, for example.

The team that conducted the test includes postdoc Michele Guala, graduate student Ian Jacobi, and Melissa Christensen, an undergraduate from UC San Diego working in McKeon's lab this summer.

Explore further: How the hummingbird achieves its aerobatic feats

Related Stories

Using science to identify true soccer stars

Jun 16, 2010

(PhysOrg.com) -- As a young boy growing up in Portugal, Luis Amaral loved playing, watching and talking soccer. Amaral and his friends passionately debated about which players were "the best." But, it was ...

Recommended for you

How the hummingbird achieves its aerobatic feats

17 hours ago

(Phys.org) —The sight of a tiny hummingbird hovering in front of a flower and then darting to another with lightning speed amazes and delights. But it also leaves watchers with a persistent question: How ...

New terahertz device could strengthen security

Nov 21, 2014

We are all familiar with the hassles that accompany air travel. We shuffle through long lines, remove our shoes, and carry liquids in regulation-sized tubes. And even after all the effort, we still wonder if these procedures ...

CERN makes public first data of LHC experiments

Nov 21, 2014

CERN today launched its Open Data Portal where data from real collision events, produced by experiments at the Large Hadron Collider (LHC) will for the first time be made openly available to all. It is expected ...

User comments : 0

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.