YS
Yash Shah
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1
Large-scale Particle Tracking Velocimetry (PTV) measurements are cond ucted in the wake of a fu ll-scale cyclist model in time-trial position at freestream velocities between 12.5 and 15 m/ s, corresponding to Reynolds numbers of the order of 5×105. Lagrangian particle tracking is employed to determine the velocity and static pressure statistics in the wake plane, showing good agreement with previous results reported in literature. The aerodynamic drag is estimated from the large-scale PTV measurements invoking the conservation of momentum in a control volume enclosing the model (PIV wake rake approach). The estimated drag follows the expected quadratic increase with increasing freestream velocity. The accuracy of the drag estimate is evaluated by comparison to state-of-the-art force balance measurements, resulting in a resolution of the PIV wake rake approach of 30 drag counts. The three terms composing the overall drag force, associated with the time-average streamwise velocity, its fluctuations and the time-averaged pressure, respectively, are evaluated separately, demonstrating that the contribution of the pressure term is negligible and the resistive force is dominated by the time-average streamwise momentum deficit.
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Large-scale Particle Tracking Velocimetry (PTV) measurements are cond ucted in the wake of a fu ll-scale cyclist model in time-trial position at freestream velocities between 12.5 and 15 m/ s, corresponding to Reynolds numbers of the order of 5×105. Lagrangian particle tracking is employed to determine the velocity and static pressure statistics in the wake plane, showing good agreement with previous results reported in literature. The aerodynamic drag is estimated from the large-scale PTV measurements invoking the conservation of momentum in a control volume enclosing the model (PIV wake rake approach). The estimated drag follows the expected quadratic increase with increasing freestream velocity. The accuracy of the drag estimate is evaluated by comparison to state-of-the-art force balance measurements, resulting in a resolution of the PIV wake rake approach of 30 drag counts. The three terms composing the overall drag force, associated with the time-average streamwise velocity, its fluctuations and the time-averaged pressure, respectively, are evaluated separately, demonstrating that the contribution of the pressure term is negligible and the resistive force is dominated by the time-average streamwise momentum deficit.
Large-scale particle tracking velocimetry is conducted in the wake of a full-scale cyclist model at 14 m/s. Particle tracks are measured in a volume of 100 x 162 x 5 cm3, from which the velocity statistics are computed. The aerodynamic drag is evaluated using the control volume approach invoking the conservation of momentum. The drag obtained from the PTV measurements closely matches that measured by an external force balance. Furthermore, it is shown that the drag force is largely due to the streamwise velocity deficit, whereas the contribution of pressure and Reynolds stress terms is minor. Finally, the drag distribution in a cross-flow plane is used to identify three regions of large velocity deficits suited for future drag minimization: the lower legs and feet, the streamwise vortical structures and the separated region over the lower back.
...
Large-scale particle tracking velocimetry is conducted in the wake of a full-scale cyclist model at 14 m/s. Particle tracks are measured in a volume of 100 x 162 x 5 cm3, from which the velocity statistics are computed. The aerodynamic drag is evaluated using the control volume approach invoking the conservation of momentum. The drag obtained from the PTV measurements closely matches that measured by an external force balance. Furthermore, it is shown that the drag force is largely due to the streamwise velocity deficit, whereas the contribution of pressure and Reynolds stress terms is minor. Finally, the drag distribution in a cross-flow plane is used to identify three regions of large velocity deficits suited for future drag minimization: the lower legs and feet, the streamwise vortical structures and the separated region over the lower back.