Aerodynamic drag determination of a full-scale cyclist mannequin from largescale PTV measurements

Abstract

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.