The secrets of a devastatingly effective horizontal bowling technique have been revealed by a team of physicists.
When bowling a cricket ball, most people tend to rotate the arm vertically about the shoulder joint. But an alternative method is to use a roundarm motion, in which a bowler extends their arm at about 90 degrees from their body, so it is almost horizontal to the ground when they release the ball.
This 鈥渟ling action鈥� technique was made famous by Sri Lankan cricketer 鈥� the first bowler to take 100 wickets across all three formats of international cricket 鈥� and is used by many bowlers.
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at Amity University Dubai in the United Arab Emirates and his colleagues have used a wind tunnel to study the air flow around a spinning cricket ball, rotating at up to 2500 revolutions per minute, to work out what happens when a ball is released from this lower horizontal bowling technique.
After the ball is released, the seam 鈥� the raised stitching around a cricket ball 鈥� spins almost parallel to the ground throughout its flight, says Sudhakaran. 鈥淥ne half of the ball has a spin direction opposite to the airflow, while the other half has a direction towards the airflow during the spinning forward motion of the ball,鈥� he says.
The team found that this causes a pressure difference that eventually leads the ball to drift laterally during its flight, either towards or away from whoever is batting.
鈥淎 higher bowling speed accompanied by a higher spin would cause an increase in lateral drift during its trajectory, which becomes useful for a bowler in deceiving a batsman,鈥� says Sudhakaran.
The magnitude of this shift is determined by the size of low-pressure zones close to the ball and how that changes due to spin. The researchers say the horizontal-arm bowlers are subconsciously employing a well-known physics concept called the , in which the spinning motion combines with airflow to produce a sideways motion.
The bending path of a football during a free kick, spin on a table tennis ball and lateral movement of a baseball are all examples of where the Magnus effect is employed by athletes, says Sudhakaran.
at RMIT University in Melbourne, Australia, says the paper answers some of the questions posed by the effectiveness of horizontal bowling, but he believes other forces on the ball will be at play too, aside from the changes in pressure.
He says the direction a spinning cricket ball travels can be dramatically altered by very small adjustments, such as where a bowler holds and releases the seam.
鈥淭he motion of the ball through the air can be bent upwards, downwards or left and right,鈥� says Watkins. 鈥淚t鈥檚 interesting to ponder that such small changes are exploited subconsciously by generations of footballers and bowlers who are often unaware of the nuances of the flow physics.鈥�
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