The influence of turbulence on cycling aerodynamics.

Many previous studies have focused on characterising Reynolds number effects and skinsuit design to better understand and improve aerodynamic performance. However, the majority of this research has been conducted in wind tunnels with turbulence intensities of less than 2%, considerably lower than that experienced when competing outdoors or in the wakes of competitors. In this systematic experimental study using passive turbulence generation, the influence of freestream turbulence on the aerodynamics of a cyclist is determined. Force measurements, wake velocity surveys, total pressure measurements and surface flow visualisations are used to characterise and quantify the aerodynamic behaviour. It is found that the aerodynamic drag is strongly affected by turbulence with it monotonically decreasing with increasing turbulence level. Moderate levels of turbulence are shown to alter local flow separation, and consequently the drag, on parts of the cyclist's body, which in turn is imprinted on the large-scale wake structures. The interaction of turbulence level and skinsuit roughness on the arms is also considered showing that these factors cannot be treated in isolation. Overall, this study highlights the importance of understanding the environment in which cyclists compete in order to optimise their performance. • The aerodynamic drag of a cyclist is highly sensitive to turbulence. • Turbulence alters local separation points of the geometry. • The development of the large-scale structures is affected by turbulence. • A smooth cyclist has lower aerodynamic drag than a skin suit in high turbulence. • Turbulence and Reynolds number have a similar effect on aerodynamic drag. [ABSTRACT FROM AUTHOR]