Aerodynamic study of different cyclist positions: CFD analysis and full-scale wind-tunnel tests |
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| Authors: | Thijs Defraeye Bert Blocken Erwin Koninckx Peter Hespel Jan Carmeliet |
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| Affiliation: | 1. Laboratory of Building Physics, Department of Civil Engineering, Katholieke Universiteit Leuven, Kasteelpark Arenberg 40, 3001 Heverlee, Belgium;2. Building Physics and Systems, Eindhoven University of Technology, P.O. Box 513, 5600 Eindhoven, The Netherlands;3. Research Centre for Exercise and Health, Department of Biomedical Kinesiology, Katholieke Universiteit Leuven, Tervuursevest 101, 3001 Heverlee, Belgium;4. Chair of Building Physics, Swiss Federal Institute of Technology Zurich (ETHZ), Wolfgang-Pauli-Strasse 15, 8093 Zürich, Switzerland;5. Laboratory for Building Science and Technology, Swiss Federal Laboratories for Materials Testing and Research (Empa), Überlandstrasse 129, 8600 Dübendorf, Switzerland;1. Monash University, Clayton, Melbourne, VIC, 3800, Australia;2. Australian Institute of Sport, Belconnen, Canberra, ACT, 2617, Australia;1. School of Sport, Exercise and Rehabilitation Sciences, University of Birmingham, Edgbaston, Birmingham B15 2TT, UK;2. School of Civil Engineering, University of Birmingham, Edgbaston, Birmingham, B15 2TT, UK;1. School of Mechanical Engineering, The University of Adelaide, Adelaide, SA, 5005, Australia;2. Australian Institute of Sport, Bruce, ACT, 2617, Australia;1. School of Sport, Exercise and Rehabilitation Sciences, University of Birmingham, Edgbaston, Birmingham, B15 2TT, United Kingdom;2. School of Civil Engineering, University of Birmingham, Edgbaston, Birmingham, B15 2TT, United Kingdom |
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| Abstract: | Three different cyclist positions were evaluated with Computational Fluid Dynamics (CFD) and wind-tunnel experiments were used to provide reliable data to evaluate the accuracy of the CFD simulations. Specific features of this study are: (1) both steady Reynolds-averaged Navier–Stokes (RANS) and unsteady flow modelling, with more advanced turbulence modelling techniques (Large-Eddy Simulation – LES), were evaluated; (2) the boundary layer on the cyclist’s surface was resolved entirely with low-Reynolds number modelling, instead of modelling it with wall functions; (3) apart from drag measurements, also surface pressure measurements on the cyclist’s body were performed in the wind-tunnel experiment, which provided the basis for a more detailed evaluation of the predicted flow field by CFD. The results show that the simulated and measured drag areas differed about 11% (RANS) and 7% (LES), which is considered to be a close agreement in CFD studies. A fair agreement with wind-tunnel data was obtained for the predicted surface pressures, especially with LES. Despite the higher accuracy of LES, its much higher computational cost could make RANS more attractive for practical use in some situations. CFD is found to be a valuable tool to evaluate the drag of different cyclist positions and to investigate the influence of small adjustments in the cyclist’s position. A strong advantage of CFD is that detailed flow field information is obtained, which cannot easily be obtained from wind-tunnel tests. This detailed information allows more insight in the causes of the drag force and provides better guidance for position improvements. |
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