Abstract
Cycling races contain a multitude of motorcycles for various activities including television broadcasting. During parts of the race, these motorcycles can ride in close proximity of cyclists. Earlier studies focused on the impact of a nearby motorcycle on cyclist drag for in-line arrangements. It was shown that not only a motorcycle in front of a cyclist but also a motorcycle closely behind a cyclist can substantially reduce cyclist drag. However, there appears to be no information in the scientific literature about the impact of the motorcycle on cyclist drag for parallel and staggered arrangements. This paper presents wind tunnel measurements of cyclist drag for 32 different parallel and staggered cyclist-motorcycle arrangements. It is shown that the parallel arrangement leads to a drag increase for the cyclist, in the range of 5 to about 10% for a lateral distance of 2 to 1 m. The staggered arrangement can lead to either a drag increase or a drag decrease, where the latter is about 2% for most positions analyzed. For one of the parallel arrangements, computational fluid dynamics simulations were performed to provide insight into the reasons for the drag increase. A cyclist power model was used to convert the drag changes into potential time gains or losses. Compared to a lone cyclist riding at a speed of 46.8 km/h (13 m/s) on level road in calm weather, the time loss by a drag increase of 10%, 4% and − 2% was 2.16, 0.76 s and − 0.80 s per km, respectively. These time differences are large enough to influence the outcome of cycling races.
Highlights
The aerodynamic resistance or drag of a cyclist is about 90% of the total resistance at racing speeds of about 40 km/h (11.1 m/s) [1,2,3]
They did not provide information on the aerodynamic drag in the riding direction, which is the focus of the present paper
The parallel position yielded an increase of cyclist drag of about 7.5%
Summary
The aerodynamic resistance or drag of a cyclist is about 90% of the total resistance at racing speeds of about 40 km/h (11.1 m/s) [1,2,3]. Much scientific research in professional cycling is focused on the reduction of cyclist drag (e.g., [4, 5]). Cycling races contain a multitude of cars and motorcycles. The motorcycles can be neutral support, commissaire, traffic manager, information, doctor, police or press motorcycles, where the latter can be camera, sound or photographer motorcycles. The motorcycles are allowed to maneuver in the proximity of the cyclists when filming. At many occasions during a race, cyclists and motorcycles are not riding in line, but in parallel (Fig. 1a) or staggered arrangement (Fig. 1b-d). The pertaining guidelines of the International Cycling Union (UCI) for “vehicle circulation in
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