Research and development of a tracking type airflow visualisation system

将稀薄的发烟剂施加到足球上，以使实际飞行中球周围的涡流可见，并通过使用高速摄像机（1，000 fps）从后面捕获图像。二维矢量图描述了球的滑流的特点，一个阶段，其中一对涡被观察到的大尺度涡结构，以及一个阶段，其中的大尺度涡结构不清楚。根据翼尖涡流和这些涡流的大尺度结构之间的类比，推测出现了与下洗有关的升力。由于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在轴向方向上缓慢旋转。这被认为是球轻微晃动的潜在原因。

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.