A Quantitative Flow Visualization Technique for On-site Sport Aerodynamics Optimization

Aerodynamics plays a crucial role in many speed sports, where races are often won by fractions of a second. A thorough understanding of the flow field around an athlete is of paramount importance to optimize the athletes’ posture, garment roughness and equipment shape to achieve the minimum aerodynamic drag and maximum velocity. To date, aerodynamic measurements are typically conducted in wind tunnels, using balances or pressure sensors. As a consequence, no information on the flow field responsible of the aerodynamic loads is gathered. Furthermore, the use of steady models yields a flow field that may differ significantly from that encountered during a race, where the athlete is in motion. The present paper proposes to use large-scale tomographic PIV for sport aerodynamic investigation. Helium-filled soap bubbles (HFSB) as flow tracers allow velocity measurements in a volume exceeding 10,000 cm3, from which the aerodynamic loads can be computed. The technique is suitable for conducting on-site aerodynamic measurements via the ring-of-fire concept: the measurements are carried out during the athletes’ training in a velodrome, thus reproducing the same flow conditions met during races.