Caltech Wind-Tunnel Test Concludes World Cup Ball Acts Goofy

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June 24 2010 11:05 AM

Caltech Wind-Tunnel Test Concludes World Cup Ball Acts Goofy

Inspired by World Cup players' complaints about the erratic flight of Adidas' new Jabulani soccer ball, a group of Caltech engineers put one into a wind tunnel , along with a traditional soccer ball. The Los Angeles Times reports that with the blower set to 30 meters per second, to simulate a good hard kick, the scientists found that the Jabulani "starts with a smooth—or laminar—airflow, shifts to something more turbulent, then shifts back again."

"So as the goalkeeper sees the ball coming, it suddenly seems to change its trajectory," [assistant professor Beverley] McKeon said. "It's like putting the brakes on, but putting them on unevenly."

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The Jabulani's behavior seems to be a result of Adidas' gimmickry in pursuit of a novel World Cup ball design:

Four years ago, the German sporting goods giant switched from the traditional 32 stitched panels to 14. The current Jabulani model — its name means "to celebrate" in Zulu — is down to eight.

Using fewer panels means the ball has fewer seams, which turns out to be something like stripping the dimples from a golf ball. Drag increases, and the flight gets more erratic.

(Confidential to Adidas: these people are called "aeronautical engineers," and sometimes they even test how air flows over stuff before it gets produced and put on the market.)

Tom Scocca is the managing editor of Deadspin and the author of Beijing Welcomes You: Unveiling the Capital City of the Future.

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