The following essay is covered in The Conversation, an online publication.
The players will use a new ball at the World Cup. A lot of work goes into making sure that every new World Cup ball feels familiar to players, because the last thing competitors want is for the most important piece of equipment to behave in unexpected ways.
I teach physics at the University of Lynchburg. There is still beauty in soccer despite the controversy surrounding the World Cup. Every four years I do an analysis of the World Cup ball to see what went into creating the most beautiful game in the world.
There are a lot of important moments in a soccer game when the ball is in the air. One of the most important characteristics of a soccer ball is how it moves.
A thin layer of air called the boundary layer surrounds some of the ball. The front half of the ball will only be covered by the boundary layer at low speeds. The wake of air behind the ball is referred to as laminar flow.
The boundary layer surrounds the ball when it's moving fast. In a series of chaotic swirls, the flow of air separates from the ball. The process is called turbulence.
The drag coefficient is a term used by physicists to calculate how much force air exerts on an object. The more drag an object feels, the faster it is.
The drag coefficients of soccer balls are 2.5 times larger than for turbulent flow. Roughening a ball's surface delays the separation of the boundary layer and keeps a ball in turbulent flow. The reason golf balls fly so far is because they feel less drag.
The speed at which the air flow transitions from turbulent to laminar is important when making a soccer ball. The ball slows down dramatically when that transition occurs. The ball slows down more quickly if the flow is too fast.
The World Cup has been hosted by Adidas. The ball was made with 32 panels. Leather was used to make the hexagonal and 12 pentagonal panels.
The World Cup was the beginning of a new era. The Teamgesit ball was made of synthetic panels that were thermally bonded together instead of stitching. Water was kept out of the interior of the ball when it was wet.
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The way the ball flies through the air can be changed by making a ball out of new materials and using fewer panels. Adidas tried to balance the panel number, seam properties and surface texture in order to create balls with the right aerodynamics.
The textured panels on the Jabulani ball were used in the 2010 South Africa World Cup. Many players complained that the Jabulani decelerated abruptly, despite Adidas efforts. The 2006 Teamgesit ball had a higher drag coefficients than the Jabulani ball, which was too smooth overall.
There were six oddly shaped panels on the World Cup balls. They had the same aerodynamic properties even though they had slightly different surfacetextures. Some players complained about the Telstar 18's tendency to pop easily.
There is a new ball for the World Cup.
The Al Rihla has 20 panels and is made with water-based ink and glue. Twelve of these are larger and shaped like an ice cream cone, and eight of them are small.
The Al Rihla is covered with features that give it a smooth feel compared to its predecessors, instead of using raisedtextures to increase surface roughness.
In order to make up for the smooth feel, the Al Rihla's seams are wider and deeper, perhaps learning from the mistakes of the overly smooth Jabulani, which had the shallowest and shortest seams of recent World Cup balls.
The wind tunnel at the University of Tsukuba was used to test the four most recent World Cup balls.
The drag coefficients rise quickly when air flow transitions from turbulent to lain flow. The ball will experience a sudden increase in drag and slow down when this happens.
The transition from ball to ball was made at a rate of 36 mph. The Jubalani has a transition speed of 51 mph. It makes sense that the Jabulani was slow and hard to predict since most free kicks start off traveling in excess of 60 mph. The Al Rihla has the same aerodynamic characteristics as its two predecessors and may even move a bit quicker at lower speeds.
The science shows that the Al Rihli should feel familiar to the players in this year's World Cup.
The conversation published this article. The original article is worth a read.
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