On the effects of crosswinds in tandem aerodynamics: an experimental and a computational study

Aerodynamics has been an important research aspect in cycling science, with aerodynamic apparel
and equipment, athlete postures, and race strategies all taking advantage of scientific aerodynamics
knowledge. Crosswinds occur when cyclists travel at a non-zero angle to the direction of the wind.
Research into crosswinds has yielded race strategies for able-bodied cyclists such as staggered drafting,
and wind conditions are recognised as a key factor to consider for cyclist safety. The impact of crosswinds
on tandem para-cyclists is less understood. Within the tandem para-cycling discipline, two athletes
compete as a team on a single bicycle with a high degree of flow interaction between both athletes. Wind
tunnel experiments and computational fluid dynamics were utilised in this research to investigate the
drag and lateral forces at yaw angles between 0◦–20◦. No single turbulence model was found superior for
all yaw angles investigated, with the SST k-ω and k-kl-ω turbulence models providing good results for
separate yaw ranges. The individual drag and lateral forces experienced by both athletes and the tandem
bicycle were investigated to provide further clarity on the distribution of wind loads for each yaw angle
tested, and to aid in identifying potential locations for aerodynamic optimisation. 15◦ yaw was found to
be the critical yaw angle where the maximum drag area of 0.337 m2 was experienced. The lateral force
exceeded the drag force by 52.8% at a yaw angle of 20◦.