Understanding the effect of seams on the aerodynamics of an association football

CARRE, M. J., GOODWILL, S. R. and HAAKE, Steve (2005). Understanding the effect of seams on the aerodynamics of an association football. Proceedings of the Institution of Mechanical Engineers, part C: Journal of mechanical engineering science, 219 (7), 657-666.

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Abstract

The aerodynamic properties of an association football were measured using a wind tunnel arrangement. A third scale model of a generic football (with seams) was used in addition to a 'mini-football'. As the wind speed was increased, the drag coefficient decreased from 0.5 to 0.2, suggesting a transition from laminar to turbulent behaviour in the boundary layer. For spinning footballs, the Magnus effect was observed and it was found that reverse Magnus effects were possible at low Reynolds numbers. Measurements on spinning smooth spheres found that laminar behaviour led to a high drag coefficient for a large range of Reynolds numbers, and Magnus effects were inconsistent, but generally showed reverse Magnus behaviour at high Reynolds number and spin parameter. Trajectory simulations of free kicks demonstrated that a football that is struck in the centre will follow a near straight trajectory, dipping slightly before reaching the goal, whereas a football that is struck off centre will bend before reaching the goal, but will have a significantly longer flight time. The curving kick simulation was repeated for a smooth ball, which resulted in a longer flight time, due to increased drag, and the ball curving in the opposite direction, due to reverse Magnus effects. The presence of seams was found to encourage turbulent behaviour, resulting in reduced drag and more predictable Magnus behaviour for a conventional football, compared with a smooth ball.

Item Type:	Article
Research Institute, Centre or Group - Does NOT include content added after October 2018:	Centre for Sports Engineering Research
Identification Number:	https://doi.org/10.1243/095440605X31463
Page Range:	657-666
Depositing User:	Ann Betterton
Date Deposited:	15 Dec 2008
Last Modified:	18 Mar 2021 11:01
URI:	https://shura.shu.ac.uk/id/eprint/648

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