Drag Kings: perfecting pedalling
“In identifying the most important aspects of the flow that influence the aerodynamic drag of cyclists, we can now more efficiently address ways to treat these flows in order improve cycling performance.” – Timothy Crouch
Elite cycling is one of the most technologically and scientifically advanced sports in the world. Many and varied advances in bicycle design, allied with sophisticated training and nutrition regimes have led to the “aggregation of marginal gains” which in turn have led to massive improvements in performance.
A key component in elite cycling performance is the aerodynamic drag of the cyclist, and much research has been devoted to optimising riding postures and equipment. However, much less attention has been paid to the effect on the drag of the essential process of pedalling.
In new research, published in Journal of Fluid Mechanics, a team of researchers at Monash University in Melbourne and the Australian Institute of Sport have used a pioneering sequence of measurements of the flow around a life-size mannequin on a bicycle in a wind tunnel to show that the drag can vary substantially (by as much as 20%) depending on the pedal location. By using innovative pressure measurements and flow visualisations, they have shown that asymmetrical pedal location (i.e. with one leg straight) has markedly more drag in the wake behind a cyclist in typical time-trial posture compared to symmetrical pedal location (i.e. with the pedals at the same height) due to asymmetry in the flow vortices in the wake, not only developing from the cyclist’s body, but even from the cyclist’s helmet.
This research has major potential to contribute further marginal gains to equipment design and cycling strategies, and demonstrates the power of modern experimental fluid dynamical research.
The Authors commented: “It’s exciting to be involved in an emerging and competitive field that drives us to investigate novel techniques and applied fluid dynamics which we see played out on the world stage.”
Flow topology in the wake of a cyclist and its effect on aerodynamic drag (T. N. Crouch, D. Burton, N. A. T. Brown, M. C. Thompson and J. Sheridan) is freely available until 30 June 2014.
The paper is also the subject of this month’s ‘Focus on Fluids’, Drag kings: characterizing large-scale flows in cycling aerodynamics written by Anette Hosoi. Focus on Fluid Review article are freely available online.