Football Aerodynamics

1. Football description

Two balls have been selected. One Nike ball consists of thirty-two panels of leather and Adidas fourteen panel ball is thermally bonded. These balls FIFA approved. A truncated Icosahedron Archimedean spherical shape is provided in thirty-two panel ball by stitching. The Adidas stitch-less fourteen panel ball is thermally bonded machine-pressed ball, and is more spherical as compared to a 32-panel ball. Wind tunnel testing was done on the ball and the sting on the ball had negligible aerodynamic effect.

  

 Fig. 1. Photographs of football [3]

 2. Results

a.  Flow Visualization

Smoke is used to visualise the airflow around the two balls understand the flow structure of the two balls.

Fig. 2. Flow field around a football inside a windtunnel [3]

The airflow over thirty-two panel ball became turbulent, due to the roughness and lead delayed flow separation. At 100° from horizontal direction, the airflow tends to occur. Generally, for a smooth surfaced sphere, the flow separation occurs normally to the horizontal axis. The surface is more spherical for the seamless fourteen panel ball, and it behaves similar to a smooth sphere. At an angle of 90 degrees from the horizontal axis flow separation is similar to that of a smooth sphere. Therefore, at low speeds, more aerodynamic drag can be generated in the 14-panel ball.

b. Aerodynamic Drag

From figure, we conclude that,

·       At high speeds, drag in a thirty-two panel ball is higher in comparison to a ball with fourteen panel.

·         Due to less spherical shape, the drag value for thirty-two panel ball changes more than that of a fourteen panel ball.

·        Variation in pressure that can be inflated has minimal effect on the aerodynamic properties of a football.

Fig. 3. Drag forces at different speeds for different panel balls [3]

Source: 3. “A Comparative Study of Football Aerodynamics” - Harun Chowdhury, Hazim Moria and Franz Konstantin Fuss, RMIT University, Melbourne.