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The surprising aerodynamics behind the Brazuca World Cup football

By

June 17, 2014

The Brazuca World Cup match ball being tested in a wind tunnel (Photo: NASA's Ames Researc...

The Brazuca World Cup match ball being tested in a wind tunnel (Photo: NASA's Ames Research Center)

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Under the guise of World Cup fever, scientists across the globe are seizing the opportunity to examine the aerodynamic properties of what will in all likelihood be the most talked-about object on a global scale over the coming weeks, the 2014 World Cup match ball. The ball, lovingly named Brazuca by the Brazilian people, is the product of a significant amount of research and money aimed at creating the ultimate centerpiece for one of the greatest sporting competitions on Earth.

You could be forgiven for thinking that a ball is in fact just a ball – a glued, seamed construction of polyurethane, kicked around a patch of earth, incapable in itself of being a source of anger or discontent. Wrong. If you dig a little deeper into the surprisingly controversial history of the World Cup match ball, you will come to realize that every facet in the design of the little sphere has an effect on the way it behaves and moves through the air. Any oversight in this design can make the ball unpredictable as was the case with the late, lamented Jabulani, a ball which exhibited aerodynamic qualities so pronounced that it was described by Brazilian striker Luis Fabian as supernatural in its movements.

The flight of a ball through the air involves a complicated mixture of aerodynamic forces. Explained at a basic level, when a ball is in motion a thin layer of air known as the boundary layer forms around the sphere. It is this boundary layer that most affects the behavior of a ball in flight. One of the aerodynamic effects that can alter the intuitive path of a ball is known as knuckling. This effect takes place when a ball is kicked with little or no spin, allowing the seams of the ball to channel the air in an unpredictable way, thus giving previous balls such as World Cup 2010's Jabulani their apparently supernatural movements. Because the ball has no initial spin, the path is dictated by pressure distribution over its surface, which is in a state of constant change. This creates an erratic fluttering motion.

A 32-panel ball being put through the Ames Research Center's water channel (Photo: NASA's ...

A 32-panel ball being put through the Ames Research Center's water channel (Photo: NASA's Ames Research Center

Adidas, the creators of the Brazuca, worked to combat the unpredictable nature of previous World Cup match balls by consulting with hundreds of active players, eventually settling on a number of techniques aimed at limiting the knuckling effect. The sports giant decided to increase the rough texture of the ball and to glue the Brazuca with six large panels compared to the eight smaller ones which made up the Jabulani.

NASA scientists at the Ames Research Center tested the Brazuca using a wind tunnel and water channel, whilst using lasers and florescent dye to highlight and simulate the aerodynamic forces acting on the ball whilst in flight. "What we are looking for in the smoke patterns is at what speed the smoke patterns suddenly change," explained Rabi Mehta, chief of the Experimental Aero-Physics Branch at the Ames Research Center. "This is when the knuckling effect is greatest."

It was found that the design of the Brazuca limited the optimal knuckling speed to only 30 mph (48 km/h), whilst the much smoother Jabulani knuckled at around 50 mph (80 km/h). This becomes relevant when considering that the average striking speed of a World Cup caliber player is 50 - 55 mph (80 - 89 km/h), almost exactly the same speeds at which the Jabulani becomes an erratic in-flight mess. Therefore, by restricting the Brazuca's knuckling speed to 30 mph, the ball becomes much more predictable for a goalkeeper to intercept. "The players should be happier with the new ball," states Mehta. "It is more stable in flight and will handle more like a traditional 32-panel ball."

NASA scientists observe the aerodynamic conditions at work around the Brazuca using smoke ...

NASA scientists observe the aerodynamic conditions at work around the Brazuca using smoke and laser light (Photo: NASA's Ames Research Center

Researchers from MIT have also been analyzing the virtues of the Brazuca's rougher surface. It is believed that this move away from progressively smoother match balls will counter a little-known phenomenon called the Magnus Effect. This aerodynamic quirk causes a very smooth ball such as the Jabulani to bend in the opposite direction compared to a rougher ball struck by the same individual. As an example, imagine a right-footed striker taking a penalty with the current rough-coated Brazuca ball. He strikes the ball towards the outside creating the intuitive right-to-left hook in the trajectory of the ball. However, if the same shot had been taken using a very smooth skinned ball, the shot would have bent in the opposite direction.

This surprising phenomenon is created by contrasting conditions in the boundary layer. A smooth ball creates a predominantly laminar flow, causing it to move contrary to the expected path of the ball, however a rougher ball creates turbulence in the boundary layer, resulting in the ball behaving in a more predictable manner. The Brazuca has seams that extend 50 percent longer than its predecessor, creating a much rougher surface and therefore ensuring that the flight of the ball is much truer to the trajectory of a traditional 32-panel ball.

In conclusion, next time you see a stunning shot arcing in from the edge of the penalty box, try not to simply think of a ball striking the back of a net, but instead quietly acknowledge the manifold aerodynamic forces at play, manipulating its path to glory.

The video below shows some of the aerodynamic tests the Brazuca underwent at NASA's Ames Research Center.

Sources: NASA, MIT

About the Author
Anthony Wood Anthony is a recent law school graduate who also has a degree in Ancient History, for some reason or another. Residing in the UK, Anthony has had a passion about anything space orientated from a young age and finds it baffling that we have yet to colonize the moon. When not writing he can be found watching American football and growing out his magnificent beard.   All articles by Anthony Wood
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9 Comments

Yes

But looks like they failed to take into account what happens on first contact with this spin. A penalty that flapped off a keepers hands in first couple of days, russian keeper spins up a ball that goes in from range from s korea, keepers desperately trying to pad balls away not risk catching. Messi goal - it lands and spins right on contacting the ground - it was going ever so slightly wide left otherwise I believe - acted like an off break in cricket as he traversed left across pitch on shooting - would normally have been scuffed right or momentum take it left. These are 3 WRONG goals down to a better ball than last time admit.

Jonathon Heart
18th June, 2014 @ 02:43 am PDT

All great physics but it really boils down on the initial spin from the contact point of the ball with the kickers foot, as in tennis or ping pong. From my limited football experience as a preteen, I believe the contact point of the boot tip on the ball is the critical parameter determining sideways or top or down movement: center of ball straight path with direction governed by seam pattern, 12 o clock, down curve, ideal for long distance lofting the ball over the goalie's head if standing forward, 3 oclock, left curve, 9 oclock, right curve, 6 oclock or conventional span contact, up spin often causing the wild kicks way above the goal.

rutnerh
18th June, 2014 @ 10:02 am PDT

What is the goal here? Effort is being made to make the new balls behave like the traditional 32 panel ball, but there's no mention of why the 32 panel ball was abandoned in the first place.

Marlon Meiklejohn
18th June, 2014 @ 10:15 am PDT

Amen Marlon! If the 32 panel ball is the standard for true and predictable flight, why are we not using it? My theory: The 32 panel ball has no fashion element, hence it can't go out of style, hence it is contrary to the goal of all sports equipment manufacturers: making something cool this year, so it will be so last year, next year :) Viva planned obsolescence!

Mac McDougal
18th June, 2014 @ 11:20 am PDT

Hey, if the knuckle optimum speed is 30 mph, then every shot will knuckle once it slows to that speed--and become unpredictable. This article needs to clarify the physics a bit more.

And, yes, why not just use the 32 panel ball!

GizEngineer
18th June, 2014 @ 02:40 pm PDT

Adidas makes 70% of the world's supply of soccer/football balls in a factory in Pakistan.

The Jabulani and Brazuca aren't the first non-traditional soccer balls made by Adidas. The company has made special ball designs for many other FIFA competitions between the World Cups and for other associations. A few designs have been made just for a single competition and never sold to the public at large. Collectors all want those but the rarity drives the price up.

As for the game, I find it flat out boring to watch with all the running around with no scoring happening, and think it's silly that it can end in a tie, or with no score at all.

Gregg Eshelman
18th June, 2014 @ 10:29 pm PDT

Exactly why is a higher-scoring ball a BAD thing?

John Gochnauer
19th June, 2014 @ 01:09 pm PDT

It is a BAD thing if it spins around like a mental jellyfish the first time it touches anything - so keepers can't catch it (they are all punching the ball away but sometimes the top top spin means the jelly-fish scrambles up and over and in the goal) shots off target spin back on target and an accurate ground passing game at speed is negated (like spain's). mind you maybe that's why they were nobbled cos everyone was impressed but bored!

Jonathon Heart
20th June, 2014 @ 08:31 am PDT

Too funny: the first of the related articles offered here is this one:

"2010 World Cup's biggest star may be the Jabulani"

That answers the "may be"...

moreover
22nd June, 2014 @ 02:44 am PDT
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