Wind tunnel investigations of cycling aerodynamics are conducted in air streams that are designed to have minimum turbulence. This is not representative of the true, turbulent wind environment encountered by a track cyclist in an indoor velodrome. The goal of this thesis, broadly speaking, is to assess the effects of this turbulence on cycling aerodynamics.
To address this question, two experimental campaigns were conducted. The first consisted of track measurements, to measure the turbulence intensities and spectra encountered in an indoor velodrome, by an isolated cyclist and by a cyclist in the far wake of another. This turbulence data was collected using a three-hole pressure probe. In the case of an isolated cyclist, it was observed that the airflow was dependent on the cyclist's location on track. A spectral analysis also revealed the presence of periodic components to the airflow, a result of the cyclist's cadence. When riding in the far wake of another cyclist, the turbulence encountered was stronger when the distance of separation got smaller.
The second experimental campaign was conducted in the wind tunnel. First, the measured track turbulence intensities and spectra were simulated using grids, for small scale, high frequency turbulence, and large obstacles, for large scale, low frequency turbulence. Once the simulated turbulence matched the track turbulence to acceptable levels, its effects on the drag of a cylinder model, representative of the cyclist's limb, were assessed. These drag measurements were conducted using an external force balance. It was found that for a smooth surfaced cylinder, free-stream turbulence was enough to trigger flow transitions and cause a reduction in the measured drag. For a rough surfaced cylinder, increasing the turbulence triggered flow transition earlier, and led to an increased Reynolds number range for the critical flow regime. It was also seen that large scale turbulence did not have a significant effect of the drag of the cylinder.