@article{oai:tsukuba.repo.nii.ac.jp:00032041,
 author = {淺井, 武 and Goff, John Eric and Asai, Takeshi and Hong, Sungchan},
 issue = {3},
 journal = {Journal of sports engineering and technology, Proceedings of the Institution of Mechanical Engineers. Part P, Journal of sports engineering and technology},
 month = {Sep},
 note = {Wind-tunnel experimental measurements of drag coefficients for non-spinning Jabulani and Brazuca balls are presented. The Brazuca ball’s critical drag speed is lower than that of the Jabulani ball, and the Brazuca ball’s super-critical drag coefficient is larger than that of the Jabulani ball. Compared to the Jabulani ball, the Brazuca ball suffers less instability due to knuckle-ball effects. Using drag data, numerically determined ball trajectories are created, and it is postulated that although power shots are too similar to note flight differences, goalkeepers are likely to note the differences between Jabulani and Brazuca ball trajectories for intermediate-speed ranges. This latter result may appear in the 2014 World Cup for goalkeepers used to the flight of the ball used in the 2010 World Cup.},
 pages = {188--194},
 title = {A comparison of Jabulani and Brazuca non-spin aerodynamics},
 volume = {228},
 year = {2014}
}