Do you know what smooth and turbulent air flow does to a cricket ball? If you don't, you've got no hope of cleaving it through the air like the greatest bowlers in the world. But don't worry, RiAus is here to get you up to speed, so the only thing standing in the way of you and a world record is, you know, a bit of freakish sporting ability.
When you swing a cricket ball the conventional way, the smooth side will make first contact with the incoming air flow, and the seam will then cause it to become turbulent as it moves past the ball. This turbulent air stays 'attached' to the ball for longer than the smooth air flow, which causes a difference in pressure on each side of the ball. The pressure is lower on the turbulent side, says the episode of A Week in Science above, which makes the ball move naturally towards the seam.
If you want to get the maximum amount of side-force on your bowl, you're going to have to be clocking speeds of up to 112 km/h (70 miles per hour). Anything over that, and you're heading into 'reverse swing' territory. At this point, the ball doesn't even need interference to experience turbulence on its surface, the turbulent air flow ends up all over the front of the ball, which means the low air pressure will end up on the opposite side of the ball. So in this mode, your ball will actually be spinning away from the seam.
If this all just went over your head, don't worry, it's a whole lot easier to understand when you watch the visuals in RiAus's video above. And how do these factors play out when you're kicking a soccer ball? That's something else you'll find out in the latest episode of A Week in Science. Just remember us when you become a world-famous sportsperson?
Source: RiAus