Written by Aerodynamic Testing
Aerodynamic testing: different protocols, same results after post-analysis
Introduction
An initial baseline assessment of the aerodynamic efficient of the cyclist was performed on the 22nd of January 2022, on a sunny day, with a temperature of 13.3 ºC, humidity of 23.31%, air density of 1.234 kg/m3 and an average wind speed of (2.34 ± 4.01) km/h. The primary goals of this intervention were to obtain benchmark values on the time trial bike for future optimisations, as well as getting information regarding the level of accuracy of the models and sensors used.
Methodology
After initial calibration procedures, two main tests were done in the same position to access the effective area of aerodynamic drag (CdA). The first block of tests consisted of several 3 km evaluations at 250 W on an out-and-back loop of 750 m, performed twice. From those 3 km samples, segments of 2.2 km were used for statistical analysis.
The second test was completed on a long stretch of road with variable terrain to maintain 220W and assess the results’ reliability. In the 12 km loop, data from 11 km were collected for statistical analysis.
Results
The first block of tests allowed us to obtain a value of the effective area of aerodynamic drag (CdA) of (0.2471 ± 0.0024 m2). As the wind was inconsistent, and it was the first time the rider was performing such tests, we obtained a relative uncertainty of 1.02 %, which is still surprisingly low, considering the unstable wind conditions.
The second test with a longer loop allowed us to obtain a value of the effective area of aerodynamic drag (CdA) of 0.2486 m2. Considering that the loop only had one braking zone and corners where the cyclist could maintain the same position, where the cyclist reduced speed by 10 km/h, the results are within the theoretical CdA values.
If we consider the kinetic energy losses when braking from 45 km/h to 35 km/h, the athlete lost 2.49 kJ of Kinetic energy in that braking zone, which would mean an increase in the calculated effective area of aerodynamic drag (CdA) given by the aerometer of 0.0011 m2 . The final 0.0005 m2 difference can be mainly attributed to cornering drag (energy loss because of the increase in rolling resistance when cornering).
Conclusions
A properly executed block of aerodynamic tests allows for a better understanding of different dynamic parameters influencing cycling performance if a proper post-analysis of the data is performed.
Optimisation of Bernardo's time-trial performance
This is part of the work developed by SpeedEdge Performance to optimise Bernardo's time-trial performance, leading to the 2022 TT National Championships and the a later hour test on the velodrome.