Caltech Puts the Jabulani Ball to the Test...

The L.A. Times brings us this story and video from Caltech, where aeronautical engineers have conducted wind-tunnel tests on Adidas' much-maligned Jabulani ball.  The results are not terribly surprising.

As the Times reports,

"Adidas produces a new ball for each World Cup and players invariably gripe. 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."

As an Engineer (Structural, not Mechanical) I'll try to explain what this means:
Basically, fewer seams leads to a lower surface roughness, making the ball's behavior in the air more erratic.  This is a gross oversimplification, as the fluid mechanics of air are even more complex than the fluid mechanics of water, but if you imagine that the ball is a ship, a traditional ball would have a regular deep keel, allowing it to sail straight through the elements, while the Jabulani would have a tiny keel, allowing it to rattle and roll with every wave.

Caltech's side-by-side wind-tunnel tests reveal this lack of stability.  In the video, you can see the air passing over the ball in laminar flow at first (the smoke is in thick sheets, pretty undisturbed).  A few seconds in, the smoke becomes less thick as the air begins to flow turbulently around the ball, before calming back to a thick laminar flow in the final second.  So while a regular soccer ball will have one trajectory and spin after being struck, the Jabulani can, and does, change it's behavior as it flies through the air.

Now, while this is a departure from the old, predictable ball, players will eventually adapt.  The true idiocy on behalf of Adidas here is not so much that the Jabulani is unpredictable, but that they insist on introducing new balls at every World Cup.  I understand that this is a perfect opportunity for marketing and gimmickry, but let's put it in perspective:
The World Cup is a competition that features the finest football players in the World, professionals that are experts at controlling a specific type of ball with their feet.  If you go and change the ball on them every time, nullifying some of their skill and experience, it's no surprise that even the most seasoned veteran can occassionally look like a schoolboy.