Was browsing through internet and came across this interesting explanation for the conventional swing and the Reverse swing. Looks pretty logical:
Conventional swing:
The principle is only applicable if there is smooth or turbulent flow on both sides of the ball i.e. similar viscosity. If the ball is thrown at low speed both sides of the ball have smooth flow. If the ball is thrown with high speed, both sides of the ball have turbulent flow. There are also speed ranges in which flow may be turbulent or smooth. These speeds are given by Reynolds number. A medium pacer uses this middle critical region of speed, where the flow may be smooth or turbulent, to swing the ball. The rough side of the ball has turbulent flow whereas the smooth side of the ball has smooth flow in this critical range of speed. Hence, air on the rough side fails to catch up with the air on the smooth side creating a low pressure region on the rough side. This tends to deviate the ball on the rough side in normal swing.
Reverse Swing:
Reverse swing can only occur when both sides of the ball has turbulent flow. This is only possible at high speeds. Bernoulli principle comes into effect at these high speeds and it makes air speed low on the rough side and fast on the smooth side. Faster speed on the smooth side leads to air being vanished more quickly on the smooth side creating a low pressure region as explained by Bernoulli principle. Hence, the reverse swing. Also, reverse swing happens late in a ball's trajectory as opposed to normal swing because ball has to first accumulate considerable portion of air to achieve turbulence. It is also possible for a ball to first swing in a normal way and then reverse its swing giving the delivery an S-shape. These S-shape swings are generally delivered by the likes of Wasim Akram.
Also, with regard to ball deviation after pitching please note that these are due to seam position/ wrist position or due to off cutter or leg cutter hand action of the bowler and has nothing to do with the swing. Cutter action is achieved in the same way as spinner action. In fact, a cutter of a fast bowler is a spinner at high speeds. Venkatesh Prasad was a master in delivering such cutters.
Also, Magnus Effect comes into play if a spinner is bowling as opposed to Bernoulli principle. There is also a phenomenon called reverse Magnus Effect.
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Topic: Conventional and Reverse Swing (Read 2619 times)