INTRODUCTION: Aerodynamics is the study of air flowing around solid bodies, where the link between velocity and pressure distribution and the resulting aerodynamic loads are of special interest. In sports, aerodynamics plays a crucial role since the drag force is a major obstacle to overcome in several different disciplines, xc-skiing being one of them. Much effort is spent studying the aerodynamics of speed sports such as speed skiing and cycling with detailed measurements of both the velocity field and pressure distribution. Aerodynamic drag in xc-skiing and its resulting effect on skiers` physiology has been studied to some extent, but not linked to the flow field itself 1,2. METHODS: Experiments were carried out with skier`s roller skiing, using the double poling technique, on a treadmill in a climatic wind tunnel 3. Two xc-skiers competing on a high national level participated in the experiments. The skiers were dressed in tight clothes normally worn during xc-skiing. The study was approved by the Swedish Ethical Review Authority (No. 2022-01049-01). The flow field at various speeds (3-7 m/s) around a single skier as well as around two skiers in line with the streaming airflow was studied. The flow field was initially visualized, revealing interesting areas for velocity measurements using particle tracking velocimetry (PTV). The flow was seeded with neutrally buoyant helium-filled soap bubbles (HFSB) as tracer particles, following the flow without affecting it. RESULTS: The study shows that the tested experimental approach has great potential to provide detailed insights, both qualitatively and quantitatively, into the flow field dynamics and the connection to drag, see Fig. 1. DISCUSSION/CONCLUSION: The experimental approach gives a possibility to visualize and measure the unsteady, turbulent wake with the complex vortex interactions directly affecting the aerodynamic drag. Detailed knowledge of the flow field around xc-skiers is necessary to enable a systematic reduction of the aerodynamic drag and potentially increase the overall performance.
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