A quasi three-dimensional visualization of unsteady wake flow in human undulatory swimming
A quasi three-dimensional visualization of unsteady wake flow in human undulatory swimming
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DOI：
10.1016/j.jbiomech.2019.06.013
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发表时间：
2019-08-27
影响因子：
2.4
通讯作者：
Takagi, Hideki
中科院分区：
文献类型：
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作者：
Shimojo, Hirofumi;Gonjo, Tomohiro;Takagi, Hideki
人体波状水下游泳（UUS）是竞技游泳中的一种水下推进技术，其推进机制尚不清楚。本研究的目的是可视化人类 UUS 过程中尾流区域的三维 (3D) 流场。一名国家级男子游泳运动员在水槽中进行了 41 次 UUS 试验。使用运动捕捉系统和立体粒子图像测速 (PIV) 设备来研究游泳者的 3D 坐标和尾流区域的 3D 流场。将一个井涌周期分为八个阶段后，我们进行坐标变换和相位平均方法来构建准3D流场。向下踢腿结束时，观察下肢外旋，双脚相互靠近。在向下冲过程中，在尾流区域观察到强烈的下游流，即射流，并且成对的涡结构伴随有射流。在涡流结构中，向下踢腿时在尾流中产生一簇涡流和喷射流，随后通过旋转腿部运动将涡流从脚上排出。这表明游泳者在向下打腿时通过在脚周围产生涡流来获得推力，涡流碰撞形成射流。本文描述、说明并解释了人类 UUS 的推进机制。 (C) 2019 Elsevier Ltd. 保留所有权利。
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. (C) 2019 Elsevier Ltd. All rights reserved.