> Researchers took the ball and fired it through a wind tunnel to measure the effect of aerodynamic forces upon it. They did so from six angles and found a consistent outcome. Regardless of where the ball was struck, if the ball reached a certain velocity it would fly faster. This, the researchers from Seoul Women’s University and the University of Tsukuba found, was down to an effect called “drag crisis”. This occurs when an object flying through the air reaches the point where the air flow around it shifts from a smooth state (known as a laminal flow) to a turbulent one. When the flow is turbulent, it disrupts the drag behind a moving object, allowing it to move faster.
> If a ball does not slow down as expected, because of the drag crisis effect, you can understand how goalkeepers may be caught unawares. The researchers found further complicating factors. They observed that while there was a drag-crisis effect regardless of where the ball was hit, the level of the crisis would shift depending on whether the ball was struck on a seam or on a panel (hitting on the seam seemed to create the lower drag). Drag crisis was also variable according to altitude, with the higher the game, the less likely the occurrence.