Flemish Cycling Federation

Brussels, Belgium

Flemish Cycling Federation

Brussels, Belgium

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Kuffi K.,Catholic University of Leuven | Defraeye T.,Catholic University of Leuven | Nicolai B.,Catholic University of Leuven | Geeraerd A.,Catholic University of Leuven | And 5 more authors.
Acta Horticulturae | Year: 2013

Fast cooling of beef carcasses has an important effect on reducing color instability in the deep muscles of the carcass. A numerical simulation of beef carcass chilling was done by using a digital scan of beef carcass geometry and measured values of flow properties. The scanning process and measurement were conducted in an industrial chiller to obtain realistic working condition for the simulation input. Simulation of 60h chilling was performed for a single and multiple carcasses. Simulation results were validated with measurements and the effect of flow direction on the cooling rate was analyzed.


Defraeye T.,Catholic University of Leuven | Blocken B.,TU Eindhoven | Koninckx E.,Flemish Cycling Federation | Koninckx E.,Catholic University of Leuven | And 3 more authors.
Journal of Biomechanics | Year: 2011

This study aims at investigating drag and convective heat transfer for cyclists at a high spatial resolution. Such an increased spatial resolution, when combined with flow-field data, can increase insight in drag reduction mechanisms and in the thermo-physiological response of cyclists related to heat stress and hygrothermal performance of clothing. Computational fluid dynamics (steady Reynolds-averaged Navier-Stokes) is used to evaluate the drag and convective heat transfer of 19 body segments of a cyclist for three different cyclist positions. The influence of wind speed on the drag is analysed, indicating a pronounced Reynolds number dependency on the drag, where more streamlined positions show a dependency up to higher Reynolds numbers. The drag and convective heat transfer coefficient (CHTC) of the body segments and the entire cyclist are compared for all positions at racing speeds, showing high drag values for the head, legs and arms and high CHTCs for the legs, arms, hands and feet. The drag areas of individual body segments differ markedly for different cyclist positions whereas the convective heat losses of the body segments are found to be less sensitive to the position. CHTC-wind speed correlations are derived, in which the power-law exponent does not differ significantly for the individual body segments for all positions, where an average value of 0.84 is found. Similar CFD studies can be performed to assess drag and CHTCs at a higher spatial resolution for applications in other sport disciplines, bicycle equipment design or to assess convective moisture transfer. © 2011 Elsevier Ltd.


Defraeye T.,Catholic University of Leuven | Blocken B.,TU Eindhoven | Koninckx E.,Flemish Cycling Federation | Koninckx E.,Catholic University of Leuven | And 5 more authors.
Journal of Biomechanical Engineering | Year: 2014

In team pursuit, the drag of a group of cyclists riding in a pace line is dependent on several factors, such as anthropometric characteristics (stature) and position of each cyclist as well as the sequence in which they ride. To increase insight in drag reduction mechanisms, the aerodynamic drag of four cyclists riding in a pace line was investigated, using four different cyclists, and for four different sequences. In addition, each sequence was evaluated for two arm spacings. Instead of conventional field or wind tunnel experiments, a validated numerical approach (computational fluid dynamics) was used to evaluate cyclist drag, where the bicycles were not included in the model. The cyclist drag was clearly dependent on his position in the pace line, where second and subsequent positions experienced a drag reduction up to 40%, compared to an individual cyclist. Individual differences in stature and position on the bicycle led to an intercyclist variation of this drag reduction at a specific position in the sequence, but also to a variation of the total drag of the group for different sequences. A larger drag area for the group was found when riding with wider arm spacing. Such numerical studies on cyclists in a pace line are useful for determining the optimal cyclist sequence for team pursuit. Copyright © 2014 by ASME.


Blocken B.,TU Eindhoven | Defraeye T.,Catholic University of Leuven | Koninckx E.,Flemish Cycling Federation | Carmeliet J.,ETH Zurich | And 2 more authors.
Computers and Fluids | Year: 2013

The aerodynamic drag of two drafting cyclists in upright position (UP), dropped position (DP) and time-trial position (TTP) is analysed by Computational Fluid Dynamics (CFD) simulations supported by wind-tunnel measurements. The CFD simulations are performed on high-resolution grids with grid cells of about 30μm at the cyclist body surface, yielding y* values well below five. Simulations are made for single cyclists and for two drafting cyclists with bicycle separation distances (d) from 0.01m to 1m. Compared to a single (isolated) cyclist and for d=0.01m, the drag reduction of the trailing cyclist is 27.1%, 23.1% and 13.8% for UP, DP and TTP, respectively, while the drag reduction of the leading cyclist is 0.8%, 1.7% and 2.6% for UP, DP and TTP, respectively. The drag reductions decrease with increasing separation distance. Apart from the well-known drag reduction for the trailing cyclist, this study also confirms and quantifies the drag reduction for the leading cyclist. This effect was also confirmed by the wind-tunnel measurements: for DP with d=0.15m, the measured drag reduction of the leading cyclist was 1.6% versus 1.3% by CFD simulation. The CFD simulations are used to explain the aerodynamic drag effects by means of the detailed pressure distribution on and around the cyclists. It is shown that both drafting cyclists significantly influence the pressure distribution on each other's body and the static pressure in the region between them, which governs the drag reduction experienced by each cyclist. These results imply that there is an optimum strategy for team time trials, which should be determined not only based on the power performance but also on the body geometry, rider sequence and the resulting aerodynamic drag of each team member. Similar studies can be performed for other sports such as skating, swimming and running. © 2012 Elsevier Ltd.


Blocken B.,TU Eindhoven | Defraeye T.,Catholic University of Leuven | Koninckx E.,Flemish Cycling Federation | Carmeliet J.,ETH Zurich | And 2 more authors.
6th European and African Conference on Wind Engineering, EACWE 2013 | Year: 2013

This paper presents a Computational Fluid Dynamics (CFD) investigation of the aerodynamic effects of drafting in cycling. In drafting, cyclists ride close behind each other to reduce aerodynamic drag. The CFD simulations for single cyclists and for a group of two cyclists are successfully compared with wind-tunnel measurements. Both CFD simulations and wind tunnel measurements show that also the leading cyclist experiences a drag reduction, which goes up to 3.1% for groups of four cyclists and more. For six or more similarly-sized cyclists riding closely behind each other, the position enjoying the largest drag reduction is the one-but-last position.

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