Aerodynamics of an in-flight football using 3D particle tracking velocimetry

Engineering of Sport 15 - Proceedings from the 15th International Conference on the Engineering of Sport (ISEA 2024)

In ball sports played at all levels, aerodynamics plays a key role. The understanding and capitalisation of these aerodynamic phenomena is evident across many sports; for example the swing of a ball in cricket or the curved flight-path of a football. It is therefore important that sports equipment behaves in a predictable and desirable way. In football for example, there are standards which govern the performance of balls with regards circumference, sphericity, rebound, water absorption, weight and pressure loss (FIFA Quality mark), but not that specifically govern in-flight behaviour of the ball. Goff (2010) provides a high level summary of the aerodynamic phenomena relevant to football. Many studies have been carried out over the last two decades and make use of wind tunnel methods, using a force balance connected to a static or spinning ball to measure drag and side force on balls of different designs. This technique allows a straight-forward quanitification of the aerodynamic behaviours of football designs for example work by Hong and Asai which show that the aerodynamic behaviour is dependant on not only panel design, but also orientation of the ball. Further studies have visualised and quantified the flow field around the ball in a wind tunnel using Particle Image Velocimetry (PIV), which allow the flow structures and shedding around the ball to be visualised and provide understanding to the ball behaviour. However, many of these studies feature balls which are fixed in position in a wind tunnel whereas in flight the ball with vary in velocity, spin and orientation. In this work, we present a new approach to measure the flow characteristics of a ball in free flight conditions.