A sports physicist reveals the science behind this year’s World Cup soccer ball

Like every World Cupwhen 2022 FIFA World Cup Players in Qatar will use new balls. The last thing competitors want is for the most important tool in the most important tournament in the world’s most popular sport to behave unexpectedly, so every new World Cup ball goes to great lengths to ensure players are familiar with it.

I am a physics professor when Lynchburg University a person who studies sports physics. Despite the corruption and human rights controversy surrounding this year’s World Cup, there is still beauty in the science and art of soccer. As part of my research, I analyze the new World Cup ball every four years to see what went into creating the centerpiece of the world’s most beautiful game.

The physics of drag

Between goal kicks, free kicks and long passes, many of the most important moments in football happen when the ball is in the air. Therefore, one of the most important characteristics of football is how it passes through the air.

As the ball moves through the air, a thin layer of mostly motionless air called the boundary layer surrounds part of the ball. At low speeds, this boundary layer covers only the front of the ball before the flowing air moves away from the surface. In this case, the air behind the ball is somewhat constant and is called laminar flow.

When the ball is moving faster, the boundary layer pushes the ball farther. When the air stream eventually breaks away from the surface of the ball, it undergoes a series of chaotic spins. This process is called turbulent flow.

At low speeds, the air will only hug the front half of the soccer ball, and it will peel off in a pattern called laminar flow, as seen in wind tunnel images.NurPhoto/NurPhoto/Getty Images

Physicists use a term called the drag coefficient to calculate how much force moving air exerts on a moving object, known as drag. For a given speed, the higher the drag coefficient, the greater the object’s drag.

It turns out that the drag coefficient of a soccer ball About 2.5 times more for laminar flow than for turbulent flow. Although it may seem counterintuitive, roughening the ball’s surface slows down the separation of the boundary layer and keeps the ball longer in the turbulent flow. This fact of physics is the reason golf balls with dents fly farther than if they were smooth.

At high speeds, the air flowing over the soccer ball moves almost completely to the back of the ball before it breaks up into a chaotic vortex called turbulence.NurPhoto/NurPhoto/Getty Images

When it comes to making a good soccer ball, the speed at which the airflow changes from turbulent to laminar is important. Because during this transition, the ball begins to slow down dramatically. If laminar flow begins at too high a speed, the ball begins to decelerate much faster than a ball that maintains turbulent flow for a long time.

Evolution of the World Cup ball

Adidas has been supplying balls for the World Cup since 1970. Until 2002, each ball was made with an impressive 32 panels. 20 hexagonal and 12 pentagonal panels were traditionally made of leather and sewn together.

A new era began with the 2006 World Cup in Germany. The 2006 Teamgeist ball consisted of 14 smooth, synthetic plates. thermally bonded together instead of stitches. A tighter, glued seal prevents water from getting inside the ball on rainy, humid days.

Making the ball with new materials, new techniques, and fewer plates changes how the ball flies through the air. During the past three World Cups, Adidas has tried to balance panel numbers, layer properties and surface textures to create just the right aerodynamic balls.

The eight-panel Jabulani ball from the 2010 World Cup in South Africa featured short seams and textured panels to compensate for the limited number of panels. Despite Adidas’ efforts, Jabulani is a controversial ball, many players are complaining that it suddenly slows down. When my colleagues and I analyzed the bomb in the wind tunnel Jabulani was generally too smooth So the 2006 Teamgeist had a higher pull factor than the ball.

The Brazuca World Cup ball in Brazil in 2014 and the Telstar 18 ball for Russia in 2018 both had six odd boards. Although they had slightly different surface textures, since they generally had the same surface roughness similar aerodynamic properties. Players in general Brazuka liked it and Telstar 18, but some complained about the attitude Telstar 18 will appear easily.

Al Rihla Ball 2022

Qatar’s new World Cup soccer ball is the Al Rihla.

Made by Al Rihla water-based inks and glues and contains 20 plates. Eight of these are small triangles with roughly equal sides, and 12 are large and shaped like ice cream cones.

Instead of using a raised texture to increase surface roughness like previous balloons, Al Rihla is coated. dimple-like features This makes its surface relatively smooth compared to its predecessor.

To compensate for the smoother feel, Al Rihla’s seam is wider and deeper – perhaps learning from the mistakes of the ultra-smooth Jabulani, which has the shallowest, shortest seam of recent World Cup balls and felt slow in the air for many players. .

Our team in Japan recently tested four World Cup balls in the wind tunnel University of Tsukuba.

Coefficient of attraction of four balls before the World Cup

The new Al Rihla ball had a lower drag coefficient at low velocities, while the 2010 Jabulani ball had more drag at higher velocities than the other three balls, resulting in faster deceleration.

As the air flow changes from turbulent to laminar flow, the drag coefficient increases rapidly, and when this happens in ball flight, the ball’s drag increases dramatically and slows down dramatically.

Most of the world championship balls we tested made this transition at about 36 mph (58 km/h). As expected, Jubalani has the most advantage with a transition speed of 51 mph (82 km/h). Most free kicks start traveling at more than 60 mph (97 km/h), so it makes sense that players found Jabulani slow and difficult to predict. There is Al Rihla aerodynamic properties are very similar with the previous two models, if anything, it might move faster, albeit at lower speeds.

Every new ball is met with complaints, but science shows that Al Rihla should feel familiar to players at this year’s World Cup.

This article was originally published Talk John Eric Goff, Lynchburg University. Read the here is the original article.

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