When the 2018 World Cup in Russia is just around the corner, fans and pseudo-fans around the world are getting ready for the carnival.
One super fan, with a special gift for the World Cup, has been doing research on the aerodynamics of the official World Cup ball since the eve of the last World Cup, with papers published in world-class publications such as Nature.
The fan scientist, Sungchan Hong, is an assistant professor in the Department of Health and exercise Science at the University of Tsukuba in Japan. In his latest paper, published in the journal of the Institution of Mechanical Engineers, he and his team conducted a comprehensive aerodynamic analysis of the official World Cup ball.
In the early years, there was no official uniform ball for the World Cup, and each national team played with its own commonly used soccer ball. In the first World Cup final, Argentina and Uruguay each played half of the game with their own footballs.
The official ball of the Russian World Cup was announced in November 2017 by the winner of the previous World Cup Ballon d 'Or, Leo Messi, and is called "Telstar 18". The name is a tribute to the Telstar, the first official World Cup ball, at the 1970 World Cup in Mexico.
Telstar, the first official ball used in the 1970 World Cup in Mexico
The World Cup football was originally made in black and white, in order to facilitate the era of color television is not popular, most fans holding black and white TV, can see clearly where the ball went at a glance.
As far as the pieces are concerned, starting with the "TV star" in 1970 and continuing until the official ball of the 2002 World Cup in Japan and South Korea, all of them are sewn from 32 pieces of "pentagon + hexagonal" leather.
From the 2006 World Cup in Germany, the official ball made by Adidas, "Team Star", made a major change: it only has 14 pieces of skin, and is hot adhesive, there is no doubt that it is rounder and smoother than the past ball.
2006 FIFA World Cup Germany Official ball "Team Star"
Since then, the official football of the World Cup has become the research subject of many scientists in the field of aerospace power research. In 2010 South Africa World Cup, Adidas launched a new design "Universal celebration", it only 8 pieces of thermal bonding fabric; The "Samba Glory", the official ball of the 2014 Brazil World Cup, has set a new record for the World Cup special ball, with a leather cover reduced to six pieces.
Telstar 18 is also made up of six leather faces, but the shape is different from the Samba Glory. The leather face of the Samba Glory is in the shape of a cross; The shape of the Telstar 18 is somewhat similar to an ancient dark weapon "blood drop" with a serrated sharp knife.
How do the different pieces of the ball affect the flight of the ball through the air? It's an aerodynamic question the Sungchan Hong team has been thinking about. The air resistance of a flying football is very complex. The simple explanation is that when the ball moves in the air, the surface of the football will form a very thin boundary layer, and it is it that affects the trajectory of the football.
So far, Dr. Hong has published several papers on the World Cup ball in some of the world's top journals, including Nature. Through wind tunnel experiments and robot simulation experiments, they have systematically analyzed the changes in the front and side forces and the movement trajectory of various kinds of balls.
2010 World Cup South Africa official ball "Celebration"
More people will probably need Dr Hong's results. Over the years, the most ridiculed World Cup ball is the "Universal Celebration" composed of eight pieces of dough, listen to the comments of the goalkeepers
Italy's Gianluigi Buffon called it "as strange as a secret weapon"; Spain's Casillas railed against its "rotten stench"; Cesar in Brazil sniffed: "Anything you pick up on the street is better than this stuff."
These are not gratuitous hatred, because the shape of "Universal Celebration" is too round, the flight path is too elegant, and the position of the demon makes the goalkeeper completely unable to predict its flight path.
Experiments have shown that at moderate speeds and above, the ball always seems to oscillate irregularly compared to other balls. The shape of the "Universal Celebration" is too round and perfect, so that the contact time of each foot is shortened, the rotation of the football is reduced, the speed is reduced, and the trajectory of the unpredictable fly.
Therefore, since Adidas opened the World Cup official ball leather reform, "Universal celebration" is the worst wind evaluation of a football, known as "expensive asshole" by the players.
The six "blood drops" fly fast and steady, and have smart chips to record data
The next in line for the Celebration, the 2014 Samba Glory, has a much better reputation.
Laboratory wind tunnel tests show that the air resistance varies with the orientation of the football surface. The effect of air resistance is the lowest for the ball with 6 pieces of fabric.
The lower the air resistance, the faster the ball, the more aggressive the ball. According to the results of Sungchan Hong's paper, when the ball is kicked by the robot, the trajectory of the ball is substantially affected by the number of pieces of fabric. "The flight trajectory of the ball with 6 pieces of leather and the traditional ball with 32 pieces of leather is relatively stable and regular compared to the ball with other numbers of leather."
"Telstar 18", using 6 pieces of dough, through seamless bonding technology, to form a complete football.
According to Dr Hong's paper, both Telstar 18 and Samba Glory perform similarly well in terms of aerodynamic coefficients. However, wind tunnel tests have shown that the Telstar 18 will fly faster over short distances with a lower drag coefficient. At medium speed (20 to 40 km/h) the pass is the most effective and flies the farthest. So, any team that plays a quick pass should have fun.
Because of the control of the instability, the ball will be more convenient for players who can use precise footwork to kick the curved ball. And the goalkeeper will be better to defend, because it is less likely to fly out of the bizarre trajectory.
Telstar 18's big breakthrough: implanted NFC smart chips
In addition to the appearance, the Telstar 18 also has a big breakthrough: the implantation of NFC smart chips. The chip is added between the second layer and the third layer of the spherical material, and when you use a smartphone to connect with the Telstar 18 through NFC technology, you can receive ball speed, ball path and other data for next study.
