Knuckle is a word without many positive connotations. Thugs use brass knuckles; people knuckle under to pressure; knuckle-dragging has never been a cool-looking locomotion technique; knuckle balls drive baseball hitters crazy; and soccer balls can "knuckle," flying through the air with an unpredictability that can earn the enmity of players.
The 2010 World Cup ball, the Jabulani, had a knuckling problem. If it was kicked with none or very little spin it would fly unpredictably. Simply put, it took some pretty crazy flight paths through the air.
To address those concerns, adidas for the 2014 Cup created the Brazuca, which, the company hoped, would handle better, and provide a truer flight path, than the Jabulani.
The Brazuca has only six panels, where the Jabulani had eight. But the seams are longer and deeper. The panels are also covered with small bumps. The overall result is a rougher ball, one built to decease the incidence of knuckling at regular kicking speeds.
Did adidas succeed? Is the Brazuca an improved soccer ball, truer in flight? The folks at NASA -- no slouches when it comes to testing objects in flight -- decided to find out.
Rabi Mehta, chief of the Experimental Aero-Physics Branch at NASA's Ames Research Center, set out to study the aerodynamics of the Brazuca. (Aerodynamics, in simple terms for we ordinary civilians, looks at how air and fluid flow around something. That something could be an airplane, a satellite or a soccer ball.)
Mehta put the Brazuca through its paces in a 2x2 wind tunnel, which blew air past the ball at varying speeds. To increase visibility of the air path around the ball, the team used a controlled flow of laser-lighted smoke over the ball's surface (see photo below).