The 2019 World Cup soccer ball has been expertly engineered for aerodynamic success

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(Inside Science) – Cristiane Rozeira’s left foot struck with the ball as soon as the whistle sounded. The ball flew over the barrier, curved gracefully to the right, touched the post and crossed the goal line. It was Rozeira’s third consecutive score of the game, and with it, she secured Brazil’s victory over Jamaica at the FIFA Women’s World Cup 2019, which is being held in France.

Score this goal was no small feat. It took expertise, but also a well-designed ball.

This year’s official ball, the Background 19has virtually the same panel design as the Telstar 18, which was the official ball for last year’s Men’s World Cup in Russia. The graphic design is different, however, as it is inspired by the 1998 tricolor ball.

The ball used in official matches is designed every four years by Adidas for the men’s World Cup and normally attracts some criticism. For example, Italian striker Giampaolo Pazzini complained that the 2010 Jabulani weighed less than usual, and German goalkeeper Marc-André ter Stegen noted that last year’s Telstar 18 “could be better”.

“The footballers playing are at the absolute elite level,” said John Eric Goff, a physicist at the University of Lynchburg in Virginia. Even though Adidas makes the technical design of the ball similar to what players expect, he said: “There are going to be small changes, not only in aerodynamics, but [also in] the way the ball feels when the texture changes slightly or the panel design changes – they’re going to notice it on their shoe.”

Players want to be able to predict the behavior of the ball in terms of bounce, roll, flight, foot speed and grip, wrote sports designer Andy Harland, director of the Sports Technology Institute at Loughborough University in the UK United, in an email to Inside Science. “The players are incredibly skilled and when they hit the ball differently they expect it to behave accordingly.”

Goff has been testing soccer balls since 2006. Last year he and colleagues Takeshi Asai and Sungchan Hong from the University of Tsukuba, Japan tested the Telstar 18 and found that the ball’s aerodynamic properties are just right for a football game.

The aerodynamics of a soccer ball are simple, but the combination of forces and variables must be just right to bend the ball’s trajectory and fool a goalkeeper.

“Once the ball has been kicked and is moving through the air, there are really very few forces acting on the ball,” said mechanical engineer Anette (Peko) Hosoi from the Massachusetts Institute of Technology. . “There’s gravity, there’s drag, and there’s lift.”

In fluid dynamics, drag – or air resistance – is a force opposing the direction of the ball. It can be influenced by the roughness and the seams of the ball. In fact, these seams are key to making a ball’s trajectory predictable. A slickball would be “terrible,” said Hosoi, who founded the MIT Sports Lab.

Imagine the air surrounding a football in full flight. A layer of air circulates around the front and creates a “messy and turbulent” area of ​​high pressure behind the ball, pushing it forward, Hosoi said. In a straight trajectory, this region would be directly behind the ball, but players like Cristiane like to spin the ball to curve its trajectory. This rotation creates a lateral force, called the Magnus force, which moves the “turbulent disorderly” region sideways and deflects the ball from its forward trajectory, Harland said.

All these forces are also influenced by temperature, atmospheric pressure and the aerodynamic properties of the balloon. “Magnus strength can be affected by the design and number of seams,” Harland said. The weather, the player’s shoes, and the outer surface of the ball also play an important role in the amount of spin, which ultimately determines the strength of the Magnus force.

Although this year’s Conext 19 only has six panels, the overall length of the balloon seam is 30% longer than the last significantly different design, which was 2014’s Brazuca. This year, Asai and Hong tested the Conext 19 in a wind tunnel and find that the aerodynamic properties are very similar to the Telstar 18, which was expected since the design is the same.

“I imagine there was no technical need to change anything,” Harland said.

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