Reverse Swerve - a New Phenomenon in Football

摘要

This paper considers the new design of footballs, which have re-duced seams and textured roughened surfaces. We propose that at specific forward and rotational (spin) velocities, the balls behave differently, with a tendency to swerve in a direction opposite from that expected. We call this proposed effect reverse swerve, and present an argument based on aerodynamics for it. This argument is developed by first considering the well-known swing and reverse swing effect of the cricket ball, reverse swing being generated because the roughened surface of an old ball triggers a turbulent boundary layer. This argument is then developed for the football. We suggest that the effect is caused by a scenario whereby, at specific forward and rotational velocities, laminar and turbulent boundary layers occur on opposite sides of the ball.