The aerodynamic efficiency of an elite cyclist is often evaluated and optimised using either one or a combination of field testing, wind-tunnel testing and numerical simulation. This study focuses on the processes and limitations involved in using a body scan to produce an accurate geometry for input to numerical simulation, with validation through drag comparisons from wind-tunnel tests and vortical wake-flow features reported in previous experimental studies. Transitional Shear Stress Transport Reynolds-Averaged Navier-Stokes simulations based on the scanned geometry were undertaken for a 180 ° half crank cycle at 15 ° increments. The sectional drag force contributions of 23 body subparts are presented, documenting the contribution and variation of each body/cycle component over the cycle. These methods are evaluated and the limitations of the approaches are discussed. The results from the numerical simulation and the wind tunnel measured drag force were very similar, differing by approximately 1%–7% for various crank angles.
The discovery of wake bistability has generated an upsurge in experimental investigations into the wakes of simplified vehicle geometries. Particular focus has centred around the probabilistic switching between two asymmetrical (bi)stable wake states of a square-back Ahmed body, however the majority of this research has been undertaken in wind tunnels operating at turbulence intensities of less than 1%. Interestingly, this is considerably lower the typical atmospheric turbulence levels. In an attempt to better simulate on-road conditions, in which turbulence intensities can easily reach levels of 15%, this study investigates the effects of free-stream turbulence on the bistability characteristics of the square-back Ahmed body. Through passive generation and quantification of the free-stream turbulent conditions, a linear correlation was determined between the switching rate and free-stream turbulence intensity, while the integrated base pressure remained unaffected over the range of turbulence levels tested.
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