Flow structure of knuckling effect in footballs
Flow structure of knuckling effect in footballs
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DOI：
10.1016/j.jfluidstructs.2011.03.016
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发表时间：
2011-07-01
影响因子：
3.6
通讯作者：
Kamemoto, Kyoji
中科院分区：
文献类型：
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作者：
Asai, Takeshi;Kamemoto, Kyoji
没有旋转或缓慢旋转的足球的飞行轨迹可能会以不可预测的方式波动，例如，在C·罗纳尔多的许多任意球中。这种反常的水平摆动或快速下落被称为“指节效应”。然而，在指节效应中影响球的空气动力学特性和边界层动力学还没有被很好地理解。在这项研究中，我们利用高速视频图像和发烟剂分析了受指节效应(指节球)影响的足球的涡旋结构特征。在球的一侧和球位与球门之间的球道前方设置了两个高速摄像机；此外，拍摄的照片速度为1000fps，分辨率为1024x512像素。尽管在先前的研究中(Taneda，1978)，在雷诺数(Re)为3.8×10(5)<；Re的光滑球体中观察到了马蹄形旋涡的脱落
The flight trajectory of a non-spinning or slow-spinning soccer ball might fluctuate in unpredictable ways, as for example, in the many free kicks of C. Ronaldo. Such anomalous horizontal shaking or rapid falling is termed the 'knuckling effect'. However, the aerodynamic properties and boundary-layer dynamics affecting a ball during the knuckling effect are not well understood. In this study, we analyse the characteristics of the vortex structure of a soccer ball subject to the knuckling effect (knuckleball), using high-speed video images and smoke-generating agents. Two high-speed video cameras were set at one side and in front of the ball trajectory between the ball position and the goal; further, photographs were taken at 1000 fps and a resolution of 1024 x 512 pixels. Although in a previous study (Taneda, 1978), shedding of horseshoe vortices was observed for smooth spheres in the Reynolds number (Re) range of 3.8 x 10(5) < Re