Abstract
The aerodynamic drag of a human-scale wind tunnel model is obtained from large-scale particle tracking velocimetry measurements invoking the conservation of momentum in a control volume surrounding the model. Lagrangian particle tracking is employed to obtain the velocity and static pressure statistics in a thin volume in the wake of a cyclist mannequin at freestream velocities between 12.5 and 15 m/s, corresponding to Reynolds numbers from 5 times 105 to 6 times 105 based on the torso length. The spatial distributions of the time-average streamwise velocity and pressure coefficient match well with previous works reported in literature. The streamwise velocity fluctuations in the wake of the cyclist’s model are presented, clearly demonstrating the unsteady nature of the main wake flow structures. Furthermore, the obtained aerodynamic drag follows the expected quadratic increase with increasing freestream velocity. The accuracy of this drag estimation is evaluated by comparison to force balance data and corresponds to 30 drag counts. The three terms composing the overall drag force, ascribed to the mean and fluctuating streamwise velocity and the mean pressure, are also evaluated separately, demonstrating that the resistive force is dominated by the contribution of the mean streamwise momentum deficit, whereas the contribution of the pressure term is negligible.Graphical abstract
Highlights
Determination of the aerodynamic loads is relevant in many fluid dynamic applications, e.g., for the fuel-efficient design of air and ground transportation systems, the safe structural design of wind turbines and the maximization of performances in elite speed sports such as cycling and skating.1 3 Vol.:(0123456789) 29 Page 2 of 11
The obtained time-average flow topology in the wake of the cyclist mannequin is discussed in terms of the spatial distribution of the streamwise velocity (Fig. 6-left) and vorticity with in-plane vectors (Fig. 6-right)
Large-scale PTV measurements have been conducted in thin volume of 5 × 100 × 160 cm3 in the wake of a full-scale cyclist model
Summary
Determination of the aerodynamic loads is relevant in many fluid dynamic applications, e.g., for the fuel-efficient design of air and ground transportation systems, the safe structural design of wind turbines and the maximization of performances in elite speed sports such as cycling and skating
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