Institute of Physical Education, Hunan University, Changsha 410082, China.
School of Industrial Design and Ceramic Art, Foshan University, Foshan 528011, China.
Int J Environ Res Public Health. 2021 Nov 22;18(22):12263. doi: 10.3390/ijerph182212263.
The study of hydrodynamic characteristics of swimming is the main way to optimize the swimming movement. The relationship between position, water depth, and swimming performance of undulatory underwater swimming are one of the main concerns of scholars. Therefore, the aim of this study is to analyze the swimming performance of three different undulatory underwater swimming positions under various swimming depths using a numerical simulation method based on multi-body motion. The simulation was conducted using 3D incompressible Navier-Stokes equations using the RNG turbulence closure equations, and in combination with the VOF method thus that we could include the water surface in our calculations. Different swimming depths based on the distance from the shoulder joint center to the initial water surface were considered. The velocity of the shoulder joint center was captured with a swimming motion monitoring system (KiSwim) and compared with the calculated results. The study found that there was a significant difference in the hydrodynamic characteristics of the three undulatory underwater swimming positions (i.e., the dorsal, lateral, and frontal positions) when swimming near the water surface, and the difference decreased as the swimming depth increased. There was a negative correlation (R(dorsal) = -0.928, R(frontal) = -0.937, R(lateral) = -0.930) between the swimming velocities of the three undulatory underwater swimming positions and the water depth (water depth = 0.2-0.7 m) and that the lateral position had the greatest average velocity. Therefore, it is recommended that swimmers travel at least 0.5 m below the water surface in any undulatory underwater swimming position in order to avoid excessive drag forces. As the swimmer approaches the water surface, the lateral position is worth considering, which has better velocity and hydrodynamic advantage than the other two undulatory underwater swimming positions.
对游泳水动力特性的研究是优化游泳动作的主要方法。波动水下游泳的位置、水深和游泳性能之间的关系是学者关注的主要问题之一。因此，本研究的目的是使用基于多体运动的数值模拟方法，分析三种不同波动水下游泳姿势在不同游泳深度下的游泳性能。模拟使用 3D 不可压缩纳维-斯托克斯方程和 RNG 紊流封闭方程，结合 VOF 方法，使我们能够将水面计算在内。考虑了基于肩节点中心到初始水面距离的不同游泳深度。肩节点中心的速度是通过游泳运动监测系统（KiSwim）捕获的，并与计算结果进行了比较。研究发现，当在水面附近游泳时，三种波动水下游泳姿势（即背侧、侧方和前方位置）的水动力特性有显著差异，随着游泳深度的增加，差异减小。三种波动水下游泳姿势的游泳速度与水深（水深=0.2-0.7m）呈负相关（R（背侧）=-0.928，R（前方）=-0.937，R（侧方）=-0.930），且侧方位置具有最大的平均速度。因此，建议游泳者在任何波动水下游泳姿势中至少在水面以下 0.5m 处游泳，以避免过大的阻力。随着游泳者接近水面，侧方位置是值得考虑的，与其他两种波动水下游泳姿势相比，它具有更好的速度和水动力优势。
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