Aerodynamic drag in cycling team time trials

In a team time trial (TTT), the main strategy is based on drafting, where team members alternately take the lead while others ride behind the leading cyclist. TTTs can contain up to 9 riders of the same team. To the best of our knowledge, systematic aerodynamic studies of drafting groups from 2 up to 9 riders have not yet been published. Therefore, this paper presents such an analysis for up to 9 drafting cyclists in a single paceline, with wheel-to-wheel spacings d = 0.05, 0.15, 0.5, 1 and 5 m. A total of 47 Computational Fluid Dynamics (CFD) simulations are performed with the 3D RANS equations, standard k-ε model and scalable wall functions and validated with wind-tunnel measurements. In groups of up to 5 identical riders with d up to 1 m, the last rider has the lowest drag but this is not the case for larger groups. A closely drafting group of 7, 8 or 9 riders has an average drag that is about half that of an isolated rider. However, for much longer theoretical single pacelines, a staggered peloton configuration can yet be about two times more drag efficient.