Cricket physics: why was Malinga’s slinging successful?

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Lasith Malinga bowling in a Sri Lanka vs Australia match of the ICC Cricket World Cup, 2019. Credit: Andy Kearns/Getty Images

 

Physicists have studied a cricket ball in a wind tunnel to understand why bowler Lasith Malinga’s career was so successful.

The study, done on bowling with a near-horizontal arm, is published in Physics of Fluids.

 

The results, write the researchers, “provide valuable insights for improving unconventional bowling techniques in cricket”.

 

Bowlers in cricket typically bowl with their arms in a nearly vertical position. Sri Lankan star Lasith Malinga had great success with a different tactic, delivering the ball from a near-horizontal arm position, with the seam almost parallel to the ground.

 

This technique, sometimes called “slinging” action, has been adopted by some other bowlers such as Malinga’s compatriot Matheesha Pathirana.

 

“The unique and unorthodox bowling styles demonstrated by cricketers have drawn significant attention, particularly emphasising their proficiency with a new ball in early stages of a match,” sys study co-author Kizhakkelan Sudhakaran Siddharth, a researcher in the department of mechanical engineering at Amity University Dubai, in the United Arab Emirates.

 

“Their bowling techniques frequently deceive batsmen, rendering these bowlers effective throughout all phases of a match in almost all formats of the game.”

 

Previous work in cricket physics has shown that the spin of the ball, as well as a combination of fluid dynamics, air speed and ball dimensions called Reynold’s number, has a big influence over how much the ball shifts mid-flight, and therefore how hard it is for a batter to hit.

 

The Amity University team studied a spinning ball inside a wind tunnel, using a device made of multiple tubes and an imaging system to understand how air moved around it.

 

“This demonstrated to be an outstanding approach for replicating the intricate and dynamic situations experienced in sports contexts within a wind tunnel setting,” says Siddarth.

 

The team found that the way low-pressure zones changed around the ball helped it make use of a phenomenon called the Magnus effect. This causes air movements that allow the ball to shift mid-flight.

 

The researchers are next interested in finding out how other factors, like wear on the ball, influence its aerodynamics.

 

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