A quasi three-dimensional visualization of unsteady wake flow in human undulatory swimming |
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| Institution: | 1. Faculty of Health Science, Department of Health and Sports, Niigata University of Health and Welfare, Japan;2. Institute for Human Movement and Medical Sciences, Niigata University of Health and Welfare, Japan;3. Department of Physical Performance, Norwegian School of Sport Sciences, Norway;4. Department of Mechanical Engineering, Meiji University, Japan;5. Faculty of Health and Sport Sciences, University of Tsukuba, Japan;6. Faculty of Health Sciences, The University of Sydney, Australia;1. School of Sports, Health and Leisure, Republic Polytechnic, Singapore;2. Japan Institute of Sports Science, Tokyo, Japan;3. Faculty of Sport Sciences, Waseda University, Saitama, Japan;4. Department of Sports, Osaka Kyoiku University, Osaka, Japan;1. Center for the Study and the Transformation of Physical Activities (CETAPS), Faculty of Sport Sciences, University of Rouen Normandy, UNIROUEN, 76821 Mont Saint Aignan, France;2. Interuniversity Biology and Motricity Laboratory (LIBM), University Savoie Mont Blanc, 73376 Le Bourget du Lac Cedex, France;3. Department of Medicine, Surgery and NeuroScience, University of Siena, Via Banchi di Sotto, 55, Siena SI, Italy;4. Sport Science Department, Medicine and Science Sport Institute, Italian National Olympic Committee (CONI), Foro Italico, Largo Lauro de Bosis 15, 00135 Roma, Italy;1. Institute of Sport, Physical Education and Health Sciences, The University of Edinburgh, St. Leonard’s Land, Holyrood Rd, Edinburgh EH8 8, United Kingdom;2. Exercise and Sport Science, FHS, C43K – K Block Cumberland Campus, The University of Sydney, Australia;1. Department of Physical Performance, Norwegian School of Sport Sciences, Oslo, Norway;2. Institute for Sport, Physical Education & Health Sciences, The University of Edinburgh, Edinburgh, Scotland, UK;3. Faculty of Sport, CIFI2D, and LABIOMEP, University of Porto, Porto, Portugal;4. Faculty of Health Sciences, The University of Sydney, Sydney, New South Wales, Australia;1. School of Sport, Ulster University, Jordanstown Campus, BT37 0QB Jordanstown, UK;2. Centre for Aquatics Research & Education, University of Edinburgh, Edinburgh, UK;3. Faculty of Health Sciences, The University of Sydney, Sydney, Australia;4. Institute of Sport, Physical Education and Health Sciences, University of Edinburgh, Edinburgh, UK |
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| Abstract: | Human undulatory underwater swimming (UUS) is an underwater propelling technique in competitive swimming and its propulsive mechanism is poorly understood. The purpose of this study was to visualize the three-dimensional (3D) flow field in the wake region during human UUS in a water flume. A national level male swimmer performed 41 UUS trials in a water flume. A motion capture system and stereo particle image velocimetry (PIV) equipment were used to investigate the 3D coordinates of the swimmer and 3D flow fields in the wake region. After one kick cycle was divided into eight phases, we conducted coordinate transformations and phase averaging method to construct quasi 3D flow fields. At the end of the downward kick, the lower limbs external rotations of the lower limbs were observed, and the feet approached towards each other. A strong downstream flow, i.e. a jet was observed in the wake region during the downward kick, and the paired vortex structure was accompanied by a jet. In the vortex structure, a cluster of vortices and a jet were generated in the wake during the downward kick, and the vortices were subsequently shed from the feet by the rotated leg motion. This suggested that the swimmer gained a thrust by creating vortices around the foot during the downward kick, which collided to form a jet. This paper describes, illustrates, and explains the propulsive mechanism of human UUS. |
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| Keywords: | PIV Dolphin kick Motion analysis Water flume |
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