03 June 2015

Women's World Cup Time!

An incredibly busy academic year, followed by preparations for leaving the country for my upcoming sabbatical year, have cut my blog writing significantly.  But a World Cup in the beautiful game is too enticing to stay away from writing.  The 2015 FIFA Women's World Cup begins this Saturday (6 June) in Canada.  FIFA isn't exactly anyone's favorite organization right now, and I doubt many people are sad to see Sepp Blatter leave his position as president of FIFA.  I sympathize with the female athletes who will have to compete in Canada on artificial turf.  It seems next to impossible to imagine male athletes being made to play their sport's biggest competition on artificial turf.  Oh well, we have to accept what's coming and try to enjoy soccer played at its pinnacle in the women's game.

For all the controversy associated with playing surfaces, I doubt there will be much controversy over the match ball.  The Adidas Context15 is a textured ball that behaves much like the Brazuca used in last year's Men's World Cup in Brazil.  My research colleagues at the University of Tsukuba in Japan, Takeshi Asai and Sungchan Hong, sent me wind-tunnel data for the new Context15.  With their permission, I show a comparison of the drag coefficients for Brazuca and Context15 in the graph below (click on the image for a larger view).
Keep in mind that 10 m/s is the same as 36 kph and a bit more than 22 mph.  The precipitous drop in the drag coefficient is the so-called "drag crisis," which is where the air flow around the ball changes from laminar to turbulent as the speed increases.  The takeaway from the above plot is that Context15 should behave similar to Brazuca.  Having the drag crises in roughly the same speed range is key to the comparison, as is the high-speed value of the drag coefficient.

A great month of soccer is coming.  The day before the Women's World Cup ends will see this year's Tour de France begin.  Two months of great sports ahead!

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