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.”

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.)