Flow interactions between two inline cyclists

Cyclists travelling in close proximity are subject to aerodynamic flow interactions. This has been observed in force results with significant drag reductions observed; particularly for the trailing rider. However, the flow mechanisms responsible have not previously been investigated. Particle Image Velocimetry was conducted on two scale model cyclists in a tandem formation in a water channel. Velocity fields showed that the wake of a trailing rider does not differ significantly from that of a single cyclist. The primary flow change was observed upstream of the trailing rider where the wake of the leader significantly decreases the streamwise velocity. This lower energy at the inflow condition for the trailing rider is the main mechanism responsible for the large drag reductions.