Every four years there is a new World Cup ball and players have to adapt to its new behavior due to changes on its aerodynamic properties. Players hated the 2010 ball—Jabulani—for its unpredictable moves. Has the new 2014 ball—Brazuca—solved these problems? NASA has the answer.
In South Africa, players said that Jabulani sucked. I remember watching the interviews with the Spanish team—the cup winners—and they all bitched about it. "It behaves like a f*cking beach ball" was the most common complain. The problem was the knuckling.
The previous World Cup ball, the Jabulani, was described as sometimes demonstrating "supernatural" movements [...] when kicked with little or no spin, the ball "knuckled," [...] Knuckling occurs when, at zero or near-zero spin, the seams of the ball channel airflow in an unusual and erratic manner making its trajectory unpredictable.
The lack of precision affected the entire game, so most players hated it. According to NASA, Adidas "worked with hundreds of players to develop the Brazuca football" to solve this "supernatural" behavior.
They introduced some changes: While a traditional football has 32 panels and Jabulani has eight, the Brazuca has only six. The Brazuca's panels also have a rougher surface.
Did the new design work?
According to Dr. Rabi Mehta, at NASA Ames Research Center, the answer is yes:
"The players should be happier with the new ball," predicted Mehta. "It is more stable in flight and will handle more like a traditional 32-panel ball."
Their aerodynamics tests show that the Brazuca's surface and paneling modifications are responsible for this improvement:
Despite having fewer panels, the finger-like panels on the Brazuca increase the seam length, compared to previous World Cup balls. The seams are also deeper than those of the Jabulani and the panels are covered with tiny bumps; all of these factors influence the ball's aerodynamics.
Indeed, Dr. Mehta says that this new roughness and panel configuration greatly affects the handling of the ball: "There is a thin layer of air that forms near the ball's surface called the boundary layer and it is the state and behavior of that layer that is critical to the performance of the ball. The materials used, the ball's surface roughness and its distribution determines its aerodynamics."
The test results
Working at the Fluid Mechanics Laboratory at NASA Ames Research Center, Dr. Mehta tested the ball in a wind tunnel and a 17-inch water channel, "which uses florescent dye dispensed into the fluid flow under black lights."
According to NASA, their tests "shows that the speed of greatest knuckling for a traditional ball is around 30 miles per hour (mph). This is well below the typical kicking speed of a World Cup-caliber player, which is about 50 to 55 mph." The Jabulani experienced knuckling at 50 mph because its smoothness, which is what drove players mad.
The Brazuca's knuckling speed is just 30 mph, so the players will have a lot more control. I can't wait to see how it affects the game. Hopefully it will be more like the national and continental leagues.
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