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Aerodynamics is the study of how air and liquids, referred to collectively as "fluids" in aerodynamics research, flow around objects. Engineers at NASA's Ames Research Center in Moffett Field, California, a world leader in fundamental aerodynamics research, possess an in-depth understanding of how fluids flow around simple three-dimensional shapes such as cylinders and spheres. With this knowledge, engineers can predict how even the minor alterations in these basic shapes change flow patterns.
The previous World Cup ball, the Jabulani, was described as sometimes demonstrating "supernatural" movements. It was beloved by strikers but hated by goalkeepers because, when kicked with little or no spin, the ball "knuckled," giving strikers a greater chance of scoring. Knuckling occurs when, at zero or near-zero spin, the seams of the ball channel airflow in an unusual and erratic manner making its trajectory unpredictable.
To address the unpredictability of the Jabulani ball, Adidas worked with hundreds of players to develop the Brazuca football. A traditional football has 32 panels, the Jabulani has eight panels and the Brazuca has only six. Despite having fewer panels, the finger-like panels on the Brazuca increase the seam length, compared to previous World Cup balls. The seams are also deeper than those of the Jabulani and the panels are covered with tiny bumps; all of these factors influence the ball's aerodynamics.
The smoother a ball is, the higher the speed at which the knuckling effect occurs. However, with the increased roughness of the Brazuca, this critical speed for maximum knuckling is reduced to about 30 mph. This is well below the typical kicking speed of a World Cup-caliber player, which is about 50 to 55 mph. So it is expected that the 2014 World Cup ball will have a more predictable flight path at typical striking speeds.
Will this make the game less exciting? The answer is no. With a new understanding of the aerodynamics of the Brazuca football, the audience, especially kids, can better appreciate the feats of skill on the field. Elite athletes will continue to manipulate the ball in amazing ways. They don't have the terms like "Bend it like Beckham" for nothing.
If given the opportunity, and/or an interest in pranks, what creative "adjustment" would you make to the balls other sports use: basketball, football (American), golf, baseball, tennis, etc?
(Score: 2) by physicsmajor on Saturday June 14 2014, @02:52AM
The XFL heavily modified the "football-like object" which they used for their brief season. There is quasi-science snake oil ALL OVER golf in the dimpling of balls; nobody has supersonic wind chambers in their basements to put that stuff to the test. Pros use whatever they want; I'm sure a bit of time with a supersonic wind chamber could get another few yards on the drive of a given ball.
Tennis does actually quite well enforcing quality control, largely because in that sport the bounce is so crucial. It's by definition a part of every point, and both parties need that ball to behave as they expect or it's trouble. Ping pong does as well for similar reasons; they increased the diameter of the ball to slow down play, but not change the characteristics.
In the former case, the ball is secondary to the goal (how far, how accurate can I throw/kick this thing) and the ball becomes more like a tool, sometimes an individual tool (golf). In those sports we observe large variation in balls used. In the latter case, the ball is an integral part of the sport itself and the objectives. Here is needs to be standardized and we see much less variation in balls.
But players will push the limits of the rules in every case, if they can gain an advantage, so this will continue.
(Score: 3, Insightful) by Foobar Bazbot on Saturday June 14 2014, @04:12AM
A supersonic wind tunnel is, just as the name implies, specialized for studying supersonic and transonic flows. While it's not impossible to establish subsonic flow in one, an ordinary wind tunnel is a cheaper and better choice for studying golf balls, which travel less than 100 m/s.