Research and development of a tracking type airflow visualisation system

一种薄薄的烟雾剂被涂在足球上，使足球周围的漩涡在实际飞行中可见，并通过高速摄像机（每秒1000帧）从后面捕捉图像。描述球滑流的二维矢量图具有一个阶段，其中一对漩涡被观察到为大尺度漩涡结构，以及一个阶段，其中大尺度漩涡结构不清楚。基于翼尖涡和这些涡的大规模结构之间的类比，推测与下洗有关的升力已经发生。这种大规模涡对结构产生的升力有时会使长轴在运动方向上的球缓慢地向轴向旋转。这被认为是球轻微摆动的潜在原因。

A thin smoking agent was applied to a soccer ball to make the vortex flow around the ball in actual flight visible, and images were captured from behind by using a high-speed video camera (1,000 fps). Two-dimensional vector diagrams depicting slipstreams of the ball featured a phase in which a pair of vortices were observed as large-scale vortex structures, as well as a phase in which the large-scale vortex structure was unclear. Based on an analogy between wingtip vortices and the large-scale structures of these vortices, a lift force related to downwash was speculated to have occurred. The lift force due to such a large-scale vortex pair structure can at times slowly rotate the ball, whose major axis is in the direction of movement, in the axial direction. This was considered to be a potential cause for the slight wobbling of the ball.