Physics holds the secret to volleyball’s highly unpredictable “float serve”

Enlarge / PARIS, FRANCE - Alen Pajenk #2 of Slovenia serves the ball during the EuroVolley 2019 Final match between Serbia and Slovenia at AccorHotels Arena on September 29, 2019 in Paris, France. (credit: Catherine Steenkeste | Getty Images)

A good float serve at just the right moment in volleyball can make or break a tight game, since the ball's trajectory is so tough to predict. It's the surface panels on conventional volleyballs that give rise to these unpredictable trajectories, and modifying the surface patterns could make for a more consistent flight, according to a recent paper in Applied Sciences.

It all comes down to gravity and aerodynamics. Any moving ball leaves a wake of air that trails behind it as it flies through the air. The inevitable drag slows the ball down. The trajectories of various sports balls are affected not just by their diameter and speed but also by any tiny irregularities on their surface. Golf balls have dimples, for example, while baseballs have stitching in a figure-eight pattern-both sufficiently bumpy to affect the airflow around the ball.

It's well known that the movement of a baseball creates a whirlpool of air around it, commonly known as the Magnus effect. The raised seams churn the air around the ball, creating high-pressure zones in various locations that (depending on the type of pitch) can cause deviations in its trajectory. Golf ball dimples reduce the drag flow by creating a turbulent boundary layer of air, while the ball's spin generates lift by creating a higher air pressure area on the bottom of the ball than on the top.

Read 9 remaining paragraphs | Comments