Liu Meng-Meng, Yu Chuan-Wen, Meng Qing-Hua, Hao Xiao-Fan, Chen Zhi-Long, He Ming
Department of Physical Education, Dongshin University, Naju, Republic of Korea.
School of Physical Education and Health, Heze University, Heze, China.
Front Bioeng Biotechnol. 2024 May 23;12:1355617. doi: 10.3389/fbioe.2024.1355617. eCollection 2024.
Gliding is a crucial phase in swimming, yet the understanding of fluid force and flow fields during gliding remains incomplete. This study analyzes gliding through Computational Fluid Dynamics simulations. Specifically, a numerical model based on the Smoothed Particle Hydrodynamics (SPH) method for flow-object interactions is established. Fluid motion is governed by continuity, Navier-Stokes, state, and displacement equations. Modified dynamic boundary particles are used to implement solid boundaries, and steady and uniform flows are generated with inflow and outflow conditions. The reliability of the SPH model is validated by replicating a documented laboratory experiment on a circular cylinder advancing steadily beneath a free surface. Reasonable agreement is observed between the numerical and experimental drag force and lift force. After the validation, the SPH model is employed to analyze the passive drag, vertical force, and pitching moment acting on a streamlined gliding 2D swimmer model as well as the surrounding velocity and vorticity fields, spanning gliding velocities from 1 m/s to 2.5 m/s, submergence depths from 0.2 m to 1 m, and attack angles from -10° to 10°. The results indicate that with the increasing gliding velocity, passive drag and pitching moment increase whereas vertical force decreases. The wake flow and free surface demonstrate signs of instability. Conversely, as the submergence depth increases, there is a decrease in passive drag and pitching moment, accompanied by an increase in vertical force. The undulation of the free surface and its interference in flow fields diminish. With the increase in the attack angle, passive drag and vertical force decrease whereas pitching moment increases, along with the alteration in wake direction and the increasing complexity of the free surface. These outcomes offer valuable insights into gliding dynamics, furnishing swimmers with a scientific basis for selecting appropriate submergence depth and attack angle.
滑行是游泳中的一个关键阶段，然而，对于滑行过程中的流体力和流场的理解仍不完整。本研究通过计算流体动力学模拟来分析滑行。具体而言，建立了一个基于光滑粒子流体动力学（SPH）方法的流 - 物体相互作用数值模型。流体运动由连续性方程、纳维 - 斯托克斯方程、状态方程和位移方程控制。采用修正的动态边界粒子来实现固体边界，并通过流入和流出条件生成稳定且均匀的流场。通过复制一个记录在案的关于圆柱体在自由表面下稳定前进的实验室实验，验证了SPH模型的可靠性。在数值模拟和实验得到的阻力和升力之间观察到了合理的一致性。验证之后，使用SPH模型分析作用在二维流线型滑行游泳者模型上的被动阻力、垂直力和俯仰力矩，以及周围的速度场和涡度场，滑行速度范围为1米/秒至2.5米/秒，浸没深度范围为0.2米至1米，攻角范围为 -10°至10°。结果表明，随着滑行速度的增加，被动阻力和俯仰力矩增加，而垂直力减小。尾流和自由表面表现出不稳定的迹象。相反，随着浸没深度的增加，被动阻力和俯仰力矩减小，同时垂直力增加。自由表面的波动及其对流场的干扰减弱。随着攻角的增加，被动阻力和垂直力减小，而俯仰力矩增加，同时尾流方向发生改变，自由表面的复杂性增加。这些结果为滑行动力学提供了有价值的见解，为游泳者选择合适的浸没深度和攻角提供了科学依据。
