The Curious Technologist-
- A 17-inch water channel, which uses fluorescent dye dispensed into the fluid flow under black lights, shows that the speed of greatest knuckling for a traditional ball is around 30 mph.
-
- The previous World Cup football was smoother and created a larger low-pressure wake behind it, pushing the speed of when it knuckled the most up to 50 mph. That’s how fast a pro kicks a football.
-
- A 2-by-2-foot wind tunnel demonstrates airflow around the Brazuca football by releasing smoke flow over the surface of the ball.
-
- Smoke is highlighted with laser light to increase flow visibility. At different speeds, there are noticeable differences in airflow around the ball.
-
- Smoke is highlighted with laser light to increase flow visibility. At different speeds, there are noticeable differences in airflow around the ball.
This is what happens when someone brings a football to NASA.
The folks at the agency’s Ames Research Center decided to take a closer look at the new ball that was designed for this year’s World Cup. The result is a lesson in fluid dynamics.
Get ready for this Sunday’s final match by reading all about how air flows around the ball here. Then annoy your friends with the scientific reason why this year’s ball has a smoother flight path than the one used during the last World Cup. Spoiler alert: Longer, deeper seams this year mean more disruption to the airflow around the ball and a smaller low-pressure wake behind it after it’s kicked.
This smaller wake leads to less “knuckling,” the erratic dipping and veering of the ball when it reaches the average professional kicking speed of around 50 mph.
“There is a thin layer of air that forms near the ball’s surface called the boundary layer and it is the state and behavior of that layer that is critical to the performance of the ball,” said Rabi Mehta, chief of Ames’s Experimental Aero-Physics Branch. “The materials used, the ball’s surface roughness and its distribution determines its aerodynamics.”
