Thesis-2011-Rogers.pdf (4.55 MB)
A study of the relationship between surface features and the in-flight performance of footballs
thesis
posted on 2011-10-03, 10:37 authored by David RogersFootball is widely regarded as the most popular sport in the world involving over 270 million
people from different countries and cultures. It can be argued that the football is one of most
important aspects of the game and hence the flight of the ball, if unexpected, can alter the
outcome of the game. This thesis provides an engineering perspective and contribution to the
continued understanding and improvement of the in-flight performance of FIFA approved
footballs.
Skilful players will impart spin onto a ball to induce a curve in-flight to try and deceive
opponents. This flight is generally smooth, although subtle variations in the orientation and spin
rate may cause conditions that affect the path and final ball position, in a manner considered to be
unpredictable due to aerodynamic effects. Ball designs and manufacturing techniques are
evolving and certain seam configurations are known to induce asymmetric pressure distributions
resulting in lateral movement during flight.
Aerodynamic research of sport balls has primarily focused on drag and the effects of high spin
rates. Studies have shown the introduction of surface roughness affects the boundary layer state
compared to a smooth sphere. Surface roughness on a football takes many forms including seam
configurations and micro surface textures. The influence of changing the density, distribution and
dimensions of the surface roughness with respect to the aerodynamic behaviour has been
researched. The principle focus of this thesis is concerned with the influence on the lateral
component as a result of applying surface roughness to the outer surfaces.
The influence of the surface roughness on the drag and lateral components were determined using
established wind tunnel techniques. Real balls and full size prototypes were tested. A
mathematical flight model was employed to simulate realistic multiple flight trajectories based on
empirical aerodynamic data. Mathematical and statistical techniques, including R.M.S and AutoCorrelation
Functions were used to analyse the data. The results from this research showed how
small variations in surface texture affected the complex nature of the lateral forces. Trajectories
varied significantly depending on initial orientation and slow spin rate sensitivities. In conclusion,
ball characterisation techniques were developed that identified lateral deviation and shape
measures and considered a gradient profiling approach. Application of these novel parameters
through multiple trajectory analysis allowed for an in-flight performance measure of footballs
designs.
History
School
- Mechanical, Electrical and Manufacturing Engineering
Publisher
© David RogersPublication date
2011Notes
A Doctoral Thesis. Submitted in partial fulfilment of the requirements for the award of Doctor of Philosophy of Loughborough University.Language
- en