Research>Aerodynamics of sports projectiles

Overview

This research is concerned with understanding the aerodynamics associated with the motion of spheres and discs used in sport. The two main areas of study are the aerodynamics of footballs and the aerodynamics of Frisbees/disc golf discs.

The aerodynamics of spheres has been actively studied since people became first interested in cannon balls, however the flow is sufficiently complex that there are still many unknowns concerning the flow around sports balls. The basics are well understood: gold balls have dimples to promote boundary layer transition and hence avoid the high pressure drag associated with laminar separation; the Magnus-Robins effect associated with spinning spheres links in with the circulation theory of lift, and with allowance for asymmetric transition, can be used to predict which way a spinning ball will swing. However, the flow physics are sufficiently complex that computational methods are not sufficiently mature as to be cost-effective for sports ball design: the normal development process is based on building and testing prototypes.

Regarding Frisbees (or disc wings), it is well known that the flight dynamic behaviour is dominated by gyroscopic forces. However, prior to the work of Jon Potts at Manchester, the effect of spin on the aerodynamics was unknown, and, as it turns, more importantly, the unique pitching moment characteristics of the Frisbee cross section were not understood.

Publications

Crowther, W.J., Potts, J.R., ‘Simulation of a spin-stabilised sports disc’, Sports Engineering (2007) 10, pp2-21, June 2007.

Potts, J. and Crowther, W.J., ‘Aerodynamics of a rotating disc wing’, Royal Aeronautical Society research forum, London, January 2000

Potts, J. and Crowther, W.J., ‘Visualisation of the flow around a rotating disc wing’, paper 247, 9^th (Millennium) International Symposium on Flow Visualisation Edinburgh, August 22-25^th, 2000.

Potts, J. and Crowther, W.J., ‘Frisbee Aerodynamics’, paper AIAA 2002-3150, 20^th AIAA Applied Aerodynamics Conference & Exhibit 24 – 26 June 2002 St. Louis, Missouri

A series of undergraduate projects on the aerodynamics of spinning footballs has been undertaken, however this work is as yet unpublished