The application of body scanning, numerical simulations and wind tunnel testing for the aerodynamic development of cyclists

Abstract

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.

Wind Tunnel Experiment for the Hydrodynamics of Wind Resistance Energy Consumption of Human Body

“…As shown in Figure 3, according to the physical feature information of athlete A such as his weight, height, and body shape, 3D scanning and printing technologies were employed to attain a 1:5 reduced-scale model of the typical postures of the athlete. After the wind tunnel experiment model which is used for drag coefficient test was scanned, a file in "stl" format was output and could be used for 3D printing or taken as the input of the numerical flow field simulation of CFD [21]. Figure 4 shows the athlete model fabricated by scanning and printing.…”

“…Figure 10 shows the wind tunnel experiment on 3D printing skier models with six typical skiing postures. In view of the force factors such as the stability of the single-foot support, when setting the wind speed conditions for the experiment, for the first four postures in Figure 10, the highest incoming wind speed was set higher, and the wind speed was adjusted at 5, 8, 10, 12, 15, 18, 20, 22, 24, 26, and 30 (m/s) respectively; while for the last two postures, the highest incoming wind speed was set lower, and the wind speed was adjusted at 5,8,10,12,15,16,17,18,19,20,21,22, and 24 (m/s) respectively. The main reason is that, both feet of the first four skier models were connected with the circular platform, while only one feet of the last two skier models (the "Push with ski poles once with every two steps" posture and the "Go uphill in a conventional way" posture) was connected to the circular platform, so the wind speed of the first group (the first four models) was set higher than that of the second group (the last two models), so as to prevent the second group models being blown off the platform due to unstable connection and causing damages to the experiment equipment.…”

Aerodynamics Analysis of Speed Skating Helmets: Investigation by CFD Simulations

“…A full-scaled skater and helmets were considered. Inspired by 2D airfoil aerodynamics CFD simulations [18] and adjusted to sports aerodynamics field, the fluid domain consisted of a quarter-sphere and semi-cylinder, providing a meshing element reduction compared to a conventional prismatic domain [19][20][21], as seen in Figure 4. The domain size was defined based on the parameters a, b, c and L (see Figure 4b), with a = 10, b = c = 5 and L = 1.1 m being the distance between the most upstream and downstream points of the skater projected on the horizontal plane.…”

“…A thorough grid sensitivity study was performed as part of the verification assessment for the bare-head case. Four grid densities (18,21,34 and 51 million elements) were tested monitoring total drag of the skater, mesh quality in terms of skewness and mean flow velocity profiles at several x and y direction rakes around the skater. All the previously mentioned parameters suffered minimal variations when the mesh was refined to 34 million elements.…”