The science of swing bowling

[rkt.india]

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Does it really matter what you call a particular type of swing? Well, it matters because the science dictates what type of swing it is. Of course, bowlers do not have to know or understand the science, but I'm sure they would appreciate knowing when a certain type of swing will be effective and in which direction the ball is likely to swing.

 

Having studied cricket ball aerodynamics for over 25 years, my mission here is to reveal the answers to all the mysteries surrounding swing bowling, and hopefully, to quash once and for all, all the myths and erroneous explanations that are still floating around the cricketing world. To assure you that these three types of swing do actually exist, and are regularly practised on the cricket ground, I have quoted examples from the famous 2005 Ashes series between England and Australia.

 

Let us first look at some of the fundamental flow physics that will help to explain all three types of cricket ball swing. As the ball is flying through the air, a thin layer of air called the "boundary layer" forms along the ball's surface. The boundary layer cannot stay attached to the ball's surface all the way around the ball and it tends to leave or "separate" from the surface at some point. The location of this separation point determines the pressure, and a relatively late separation results in lower pressure on that side. A side force or swing will only be generated if there is a pressure difference between the two sides of the ball.

 

Now the boundary layer can have two states: a smooth and steady "laminar" state, or a time-varying and chaotic "turbulent" state. The transition from a laminar to a turbulent state occurs at a critical speed that is determined by the surface roughness; the rougher the surface the lower the critical speed. However, on a very smooth surface and at nominal speeds, a laminar boundary layer can be forced to turn turbulent by "tripping" it with a disturbance. The disturbance can be in the form of a local protuberance or surface roughness which adds turbulent eddies to the laminar layer and forces it to become turbulent. It is similar to putting your finger into a smooth stream of water from a tap: note how small chaotic turbulent motions are generated downstream of the finger location. Now it turns out that a turbulent boundary layer (because of its increased activity and energy) can stay attached to the ball's surface for a longer distance compared to a laminar layer.

 

http://www.espncricinfo.com/story/_/id/23193364/truth-conventional-reverse-contrast-swing

 

Great article to understand difference between reverse and contrast swing. Most times what we see with the old ball is contrast swing and people refer to it has reverse swing. 

[Inside my Jamshed]

Good article, makes me think of the times before I made my first 10 crore as a young Punjabi watching Wasim and Waqar destroy attacks

[LORD_analyst]

On 5/6/2018 at 4:17 AM, Inside my Jamshed said:

Good article, makes me think of the times before I made my first 10 crore as a young Punjabi watching Wasim and Waqar destroy attacks

and when the bottle caps weren't available....getting spanked and pulling up  hamstrings.

[Sean Bradley]

On ‎5‎/‎6‎/‎2018 at 4:17 AM, Inside my Jamshed said:

Good article, makes me think of the times before I made my first 10 crore as a young Punjabi watching Wasim and Waqar destroy attacks

Your name suggest you are a pathan, are you ?