Aerodynamic Performance of Cycling Time Trial Helmets (P76)

Blair, Kim B.; Sidelko, Stephanie

doi:10.1007/978-2-287-09411-8_44

Cited by 9 publications

(4 citation statements)

References 3 publications

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“…Regardless of the underlying input parameters in the power meter model, both small-and large scale deltas are well captured by both the Ring of Fire technique and the power meter approach and agree with available literature values (Barry et al, 2014;Blair et al, 2009;Spoelstra et al, 2019). The uncertainty on the average drag measurements from the RoF is within 5%.…”

Section: Discussionsupporting

confidence: 76%

Uncertainty assessment of the Ring of Fire concept for on-site aerodynamic drag evaluation

Spoelstra

Hirsch

Sciacchitano

et al. 2021

Meas. Sci. Technol.

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The Ring of Fire (RoF) measurement concept to perform on-site experiments of aerodynamic drag for transiting objects is investigated with a study that identifies the main sources of uncertainty.The main contributors to the uncertainty of the drag measurement are examined for the case of a cyclist riding through the measurement domain. A sensitivity analysis is conducted that assesses how the estimated drag is affected by the choice of PIV image processing parameters. The size of the crosssection considered in the control volume formulation is also investigated. It is found that the accuracy of the estimated drag depends on the procedure used to detect the edge of the momentum deficit region in the wake. Moreover imposing mass conservation yields the most accurate drag measurements. The drag estimation has little dependence upon the spatial resolution of the measurement as long as the interrogation window size stays within 5% to 25% of the equivalent diameter of the object cross section. Experiments are conducted in a sport-hall, where the aerodynamic drag estimates from the RoF are compared to a conventional torque power meter installed on the bicycle, and different rider's postures as well as equipment variations are considered.Although the discrepancy in the absolute value of drag can be as high as 20%, power metering and RoF agree within 4% on relative drag variations.

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Section: Discussionsupporting

confidence: 76%

Uncertainty assessment of the Ring of Fire concept for on-site aerodynamic drag evaluation

Spoelstra

Hirsch

Sciacchitano

et al. 2021

Meas. Sci. Technol.

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“…Many of these events are won or lost by only seconds. Small reductions in overall aerodynamic drag can easily save seconds in any of these events, giving the athlete a decisive advantage [2]. Approximately 2 to 8 percent of the athlete's total drag is a result of their helmet [1].…”

Section: [B] (Figure 1) Production Aerodynamic Helmet Head Positions mentioning

confidence: 99%

“…During longer events it is very difficult for an athlete to keep their head up and maintain this helmet position. Blair and Sidelko [2] performed an aerodynamic analysis of ten production aerodynamic helmets to study their performance. They also tested a standard non-aerodynamic road helmet for comparison.…”

Section: [B] (Figure 1) Production Aerodynamic Helmet Head Positions mentioning

confidence: 99%

Aerodynamic Bicycle Helmet Design Using a Truncated Airfoil With Trailing Edge Modifications

Sims

Jenkins

2011

Volume 6: Fluids and Thermal Systems; Advances for Process Industries, Parts a and B

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Aerodynamic drag contributes the majority of the resistance experienced by a competitive cyclist. Low aerodynamic drag is a key quality of high performance equipment and many aerodynamic helmets have been developed. These helmets are designed with a teardrop shape that attempts to maintain attached air flow. This shape provides a drag reduction when the athlete has their head up and is looking forward but has adverse effects if the athlete rotates their head down. A helmet design that helps maintain attached airflow while presenting reduced frontal area when the athlete’s head is down could significantly improve performance. The aerodynamic improvements of applying a truncated airfoil shape with a trailing edge modification to a helmet design were investigated. SolidWorks Flow Simulation was used to evaluate the aerodynamic forces. A common production helmet design was progressively truncated to determine the optimal truncation length and the effects of multiple trailing edge modifications were tested. A specific truncation length with a trailing edge base cavity was found to provide similar head up performance but significantly better head down performance compared to the production design. Scale models of the final improved design and the production helmet were tested in the wind tunnel to verify the computational results.

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“…9,10 Given the large potential of improved cycling performance, past research focused on reduction of aerodynamic drag through modification to riding position 4,6,7,9,11–15 or equipment. 2,8,10,16–21 Grappe et al 4 reported up to 27% reduction in drag area in the O’bree position compared to upright, dropped and aero positions, which indicates the possibility for rider position optimization for reduction in aerodynamic drag. Similarly, Garcia-Lopez et al 14 reported reference values of aerodynamic drag of professional cyclists as measured in a wind tunnel in five riding positions under static and dynamic conditions.…”

Section: Introductionmentioning

confidence: 98%

Predictive mathematical model of time saved on descents in road cycling achieved through reduction in aerodynamic drag area

Drory

Yanagisawa

2012

Proceedings of the Institution of Mechanical Engineers, Part P:

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This paper presents empirically-based simulation results of descent time to completion in road cycling. A mathematical model is formulated to predict time saved on road cycling descents where a cyclist's position is static through manipulation of aerodynamic drag area, system parameters and initial conditions. Road cyclists often adopt drastic static riding positions on long descents in order to minimize aerodynamic drag and optimize performance, measured as race time to completion. In those riding positions bicycle control is compromised and the risk of fall and injury increases.The aims of this study were to empirically determine whether there is a difference in aerodynamic drag area associated with the 'Top-Tube' descending riding position compared to 'Normal' descending riding position, and to investigate the effect of the difference on time to completion of road descents.Two elite male Australian time-trial cyclists were tested in an open jet wind tunnel. Drag force was measured using a force platform and a custom air bearing drag measurement system at 50 Hz at wind velocity of 15.6 m/s. Athletes were tested in their 'Normal' descending position and in the 'Top-Tube' position. Based on Newtonian-Lagrangian equations of motion of the cyclist-bicycle system, an analogue mathematical model as a non-linear Riccati ordinary differential equation was developed to enable prediction of velocity and time to completion of a road cycling course descent of known length and gradient as measures of performance for an athlete of known mass and empirically determined drag area in a descending position. Previously, proposed models of cycling performance have been based on physiological, anthropometric, and mechanical power output. No general closed-form time-to-completion mathematical model for cycling was found in the literature. Analytical solutions allow for a concise investigation of a dynamical system model behaviour that is not as readily available with a numerical solution.Wind tunnel testing showed up to 25% reduction in drag area for changes to cyclists riding position from their 'Normal' to the 'Top-Tube' dropped descending position. The analytical solution to the nonlinear Riccati differential equation showed that large time savings as a result of reduction of drag area can be made on road cycling race descents. In the example scenario simulated here, 29.2 s may be saved on a 5 km descent of 10% gradient with 25% reduction in aerodynamic drag area (CdA).The 'Top-Tube' riding position is associated with a large reduction in aerodynamic drag area in road descents compared to conventional descending riding position. Our model enables the prediction of time to completion on descents. This may assist cyclists to assess the trade-off between undertaking increased risk associated with drastic rider descending position and the potential for improved performance in the context of race tactics and strategy.

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Aerodynamic Performance of Cycling Time Trial Helmets (P76)

Cited by 9 publications

References 3 publications

Uncertainty assessment of the Ring of Fire concept for on-site aerodynamic drag evaluation

Uncertainty assessment of the Ring of Fire concept for on-site aerodynamic drag evaluation

Aerodynamic Bicycle Helmet Design Using a Truncated Airfoil With Trailing Edge Modifications

Predictive mathematical model of time saved on descents in road cycling achieved through reduction in aerodynamic drag area

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