Dominant Flow Structures In The Wake of A Cyclist

Crouch, Timothy; McGrath, Brian E.; Thompson, Mark C.; Waithe, Kenrick A.; Burton, David; Morris, Steven L.; Sheridan, John

doi:10.2514/6.2012-3212

Cited by 6 publications

(8 citation statements)

References 1 publication

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“…The results presented in the following sections are the mean of at least two consecutive runs sampled over 30 s. As indicated above, it has been shown that the drag of a cyclist varies with leg position around the crank cycle. 26–28 This variation is also seen in the oscillating drag force during dynamic tests. For this reason, it is necessary to sample over-sufficiently many cycles, such that the mean is effectively independent of the leg start and end positions.…”

Section: Experimental Methodologymentioning

confidence: 70%

“…In addition to the similar frontal area, this may be the result of disruption in the flow between the arms that normally flows under the torso and out over the hips and between the legs. 24–26…”

Section: Resultsmentioning

confidence: 99%

“…It has been shown that the position of the legs has a profound influence on the flow behaviour and consequently the flow structure in the wake. 26–28 The wake flow topology has been shown to be dominated by the position of the legs in combination with the general human form. However, at present, it is not clear how controllable changes in the rider posture on the bike influence the flow field around the body and the structure of the wake, which in turn influence the overall drag.…”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Aerodynamic performance and riding posture in road cycling and triathlon

Barry

Burton

Sheridan

et al. 2014

Proceedings of the Institution of Mechanical Engineers, Part P:

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Cycling performance is strongly dependent on aerodynamic drag, of which the majority is attributable to the rider. Previous studies have shown the importance of optimising athlete posture on the bicycle for individual time-trial events. This article identifies that performance in road cycling and draft-legal triathlon can be improved through aerodynamic optimisation of the athlete’s posture. Nine relevant cycling postures have been studied, and it was found that for road cycling, gripping the hoods with horizontal forearms can reduce the required cyclist power by 13.4%, and for draft-legal triathlon applications, the use of short bar extensions reduced the required power by up to 16.7%. It was also found that lowering the eyes and head increased drag in both drops and triathlon postures. Measurements of the velocity profiles of the wake of a cyclist in four different postures are presented, and it is shown that differences in drag coefficients between postures can be correlated with changes in the wake velocity defect and turbulence intensity distribution.

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Section: Experimental Methodologymentioning

confidence: 70%

Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Aerodynamic performance and riding posture in road cycling and triathlon

Barry

Burton

Sheridan

et al. 2014

Proceedings of the Institution of Mechanical Engineers, Part P:

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“…Using wind tunnel observation, characterisation of the variation of the flow with static crank angle has been reported in [9] and [10]. The approach taken was to manufacture a posable mannequin based on a generic cyclist.…”

Section: Methodsmentioning

confidence: 99%

“…The current paper has three aims: (i) to build upon earlier wind-tunnel based work in our group [9] and further characterize the variation of the flow with crank angle, (ii) to compare flow behaviour observed experimentally with CFD results, in order to assess the current capability to numerically model cyclist aerodynamics, and (iii) to build a foundation from which the more challenging problem of a dynamic, pedalling cyclist CFD model can be developed.…”

Section: Accepted Manuscript N O T C O P Y E D I T E Dmentioning

confidence: 99%

Computational Fluid Dynamics Study of the Effect of Leg Position on Cyclist Aerodynamic Drag

Griffith

Crouch

Thompson

et al. 2014

Journal of Fluids Engineering

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An experimental and numerical analysis of cycling aerodynamics is presented. The cyclist is modeled experimentally by a mannequin at static crank angle; numerically, the cyclist is modeled using a computer aided design (CAD) reproduction of the geometry. Wind tunnel observation of the flow reveals a large variation of drag force and associated downstream flow structure with crank angle; at a crank angle of 15 deg, where the two thighs of the rider are aligned, a minimum in drag is observed. At a crank angle of 75 deg, where one leg is at full extension and the other is raised close to the torso, a maximum in drag is observed. Simulation of the flow using computational fluid dynamics (CFD) reproduces the observed variation of drag with crank angle, but underpredicts the experimental drag measurements by approximately 15%, probably at least partially due to simplification of the geometry of the cyclist and bicycle. Inspection of the wake flow for the two sets of results reveals a good match in the downstream flow structure. Numerical simulation also reveals the transient nature of the entire flow field in greater detail. In particular, it shows how the flow separates from the body of the cyclist, which can be related to changes in the overall drag.

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