Improving swimming performance through detailed flow measurements

由于与动态自由表面相互作用、海崖体流动分离、大的非定常运动和软变形几何形状相关的复杂流动机制，预测和测量作用在游泳运动员身体上的流体力是非常具有挑战性的。性能运动工程实验室在过去的9年里通过一系列博士生支持英国游泳队，然而，仍然存在与测量和理解围绕游泳者发展的详细流动结构以及这些流动结构如何与人体相互作用相关联的明显挑战。作用在身体上的推进力和阻力都受这些非定常流动特征的支配，因此提高我们对流动物理和生物力学的理解对于提高游泳成绩至关重要。关于如何优化不同运动员的划水技术以最大限度地提高成绩，人们知之甚少。例如，在水下波动游泳中，推进力由波浪状的身体运动产生，这已经被证明在游泳者后面产生一系列涡流结构，增加了所产生的推力。除此之外，不稳定流动分离和自由表面相互作用使得阻力难以预测。评估这些复杂的流场非常具有挑战性，因此游泳者的效率和表现通常仅基于最大游泳速度来评估。最近的发展，在数值模拟已经有可能模拟一些这种流动物理，但目前还没有实验数据来验证这些不稳定的流场在swiming.This项目的目的是与英国游泳，英国体育学院和Speedo了解物理流动机制与游泳阻力和推进通过使用详细的流量测量。游泳运动员周围的局部流动特征将以各种不同的方式进行评估，并增加保真度。最初，将使用气泡片来识别感兴趣的关键区域，以允许将流动可视化与中风运动学和关键性能指标（如最大速度）进行比较。详细的流动测量周围的可变形人体模型将进行内Boldrewood拖曳坦克使用新的水下粒子图像测速（PIV）系统。水下数字图像相关（DIC）将用于评估身体的全场变形和泳衣对被动阻力的影响。为了量化一个实际游泳者周围的非定常流场，将开发一个气泡图像测速系统，以允许在游泳池环境中进行测量。通过与英国游泳和Speedo的合作，这项研究有可能对游泳衣技术和英国在奥运会上的表现产生真实的影响。

Predicting and measuring the fluid forces acting on a swimmer's body is incredibly challenging due to the complex flow mechanisms associated with dynamic free surface interactions, bluff body flow separation, large unsteady motions and soft deformable geometries.The Performance Sports Engineering Laboratory has supported the British Swimming team for the last 9 years through a series of PhD students, however there is still a distinct challenge associated with measuring and understanding the detailed flow structures that develop around a swimmer and how these interact with the human body. Both the propulsive forces and the drag acting on the body are governed by these unsteady flow features therefore improving our understanding of the flow physics and biomechanics is essential to improving swimming performance. Little is known about how to optimise stroke technique for different athletes to maximise performance. For instance in underwater undulating swimming the propulsive force is generated by a wave like body motion which has been shown to create a series of vortex structures behind the swimmer, increasing the thrust generated. In addition to this the unsteady flow separation and free surface interactions makes the resistive forces difficult to predict. These complex flow fields are very challenging to assess and therefore a swimmer's efficiency and performance is typically only assessed based on maximum swimming speed. Recent developments in numerical modelling have made it possible to simulate some of this flow physics however there is currently no experimental data available to validate these unsteady flow fields in swimming.This project aims to work with British Swimming the English Institute of Sport and Speedo to understand the physical flow mechanisms associated with swimming resistance and propulsion through the use of detailed flow measurements. The local flow features that develop around a swimmer will be assessed in a variety of different ways with increasing levels of fidelity. Initially key areas of interest will be identified using a bubble sheet to allow flow visualisation to be compared to stroke kinematics and key performance indicators such as maximum velocity. Detailed flow measurements around a deformable mannequin will be conducted within the Boldrewood towing tank using the new underwater Particle Image Velocimetry (PIV) system. Underwater Digital Image Correlation (DIC) will be used to assess the full field deformation of the body and the impact of swim suits on the passive resistance. To quantify the unsteady flow field around an actual swimmer a bubble image velocimetry system will be developed to allow measurements to be taken in a swimming pool environment. Through the involvement with British Swimming and Speedo this research has the potential to have real impact on both swim suit technology and British performance at the Olympic games.