Abstract
Aerodynamic flow around an 1/5 scale cyclist model was studied experimentally and numerically. First, measurements of drag force were performed for the model in a low-speed wind tunnel at Reynolds numbers from 5.5 times 10^{4} to 1.8 times 10^{5}. Meanwhile, numerical computation using a large eddy simulation method was performed at three Reynolds numbers of 1.1 times 10^{4}, 6.5 times 10^{4} and 1.5 times 10^{5} to obtain the drag coefficients for comparison. Second, flow visualization was made in a water channel and the wind tunnel mentioned to examine the three-dimensional flow separation pattern on the model surface, which could also be realized from the numerical results. Finally, a wake flow survey based on the hot-wire measurements in the wind tunnel showed that in the near-wake region, the flow was featured with the formation of multiple streamwise vortices. The numerical results further indicated that these vortices were evolved from the separated flows occurred on the model surface.Graphic
Highlights
When cycling at reasonably high speed, the drag due to a cyclist can be much greater than that resulted from the bicycle being ridden
We assume that the flow characteristics around the cyclist model be insensitive to the Reynolds numbers over the range obtained in the water channel and wind tunnel experiments, the largescale flow structures revealed by flow visualization in these two facilities
The results obtained indicate that the numerical approach can complement the experimental method satisfactorily in obtaining the drag coefficient as well as gaining the insightful information of the aerodynamic flow around the cyclist body
Summary
When cycling at reasonably high speed, the drag due to a cyclist can be much greater than that resulted from the bicycle being ridden. Evidence reported in the literature indicates that during cycling at a racing speed of 50 km/h, aerodynamic drag can contribute about 90% of the total drag (Kyle and Burke 1984), of which 70% is due to the cyclist. Defraeye et al (2010a) conducted a numerical and experimental study for a cyclist at the upright, dropped and time trial positions, respectively. Experiments were made in a large-scale wind tunnel that a cyclist with a racing bicycle was situated in the test section for aerodynamic drag measurements. The numerical and experimental results on the values of drag area and the pressure coefficients at different locations on the cyclist body were compared. The results obtained by the two approaches were in good agreement, which inferred that the method of numerical
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