Understanding the Effect of Seams on the Aerodynamics of an Association Football
Understanding the Effect of Seams on the Aerodynamics of an Association Football
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了解接缝对足球空气动力学的影响
DOI：
10.1243/095440605x31463
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发表时间：
2005
期刊：
影响因子：
--
通讯作者：
S. Haake
中科院分区：
文献类型：
--
作者：
M. Carré;S. Goodwill;S. Haake
摘要利用风洞装置对足球的空气动力学特性进行了测量。除了“迷你足球”外，还使用了通用足球的第三比例模型（带接缝）。随着风速的增加，阻力系数从0.5下降到0.2，表明边界层中的层流行为转变为湍流行为。对于旋转的足球，观察到马格努斯效应，并发现在低雷诺数下反向马格努斯效应是可能的。对旋转光滑球体的测量发现，层流行为导致大范围的雷诺数的高阻力系数，马格努斯效应是不一致的，但一般显示在高雷诺数和旋转参数的反向马格努斯行为。任意球的轨迹模拟表明，在中心被击中的足球将遵循接近直线的轨迹，在到达球门之前略微倾斜，而在中心被击中的足球将在到达球门之前弯曲，但将具有明显更长的飞行时间。对于光滑球重复弯曲踢球模拟，这导致由于阻力增加而导致更长的飞行时间，并且由于反向马格努斯效应而导致球在相反方向上弯曲。研究发现，与光滑的球相比，接缝的存在会促进湍流行为，从而减少阻力，并使传统足球的马格努斯行为更具可预测性。
Abstract The aerodynamic properties of an association football were measured using a wind tunnel arrangement. A third scale model of a generic football (with seams) was used in addition to a ‘mini-football’. As the wind speed was increased, the drag coefficient decreased from 0.5 to 0.2, suggesting a transition from laminar to turbulent behaviour in the boundary layer. For spinning footballs, the Magnus effect was observed and it was found that reverse Magnus effects were possible at low Reynolds numbers. Measurements on spinning smooth spheres found that laminar behaviour led to a high drag coefficient for a large range of Reynolds numbers, and Magnus effects were inconsistent, but generally showed reverse Magnus behaviour at high Reynolds number and spin parameter. Trajectory simulations of free kicks demonstrated that a football that is struck in the centre will follow a near straight trajectory, dipping slightly before reaching the goal, whereas a football that is struck off centre will bend before reaching the goal, but will have a significantly longer flight time. The curving kick simulation was repeated for a smooth ball, which resulted in a longer flight time, due to increased drag, and the ball curving in the opposite direction, due to reverse Magnus effects. The presence of seams was found to encourage turbulent behaviour, resulting in reduced drag and more predictable Magnus behaviour for a conventional football, compared with a smooth ball.