Fast Bowling - Swing Bowling

Swing Bowling

Swing bowlers cause the ball to move laterally through the air, rather than off the pitch like seam bowlers. Normal or conventional swing bowling is encouraged by the raised seam of the ball, and conventional swing is usually greatest when the ball is new and therefore has a pronounced seam. As the ball gets older, the wear makes swing more difficult to achieve, but this can be countered if the fielding team systematically polishes one side of the ball while allowing the other to become rough. When the ball has been polished highly on one side and not on the other and if the ball is bowled very fast (over 85 miles per hour), it produces a reverse swing such that the ball swings in the opposite direction as in conventional swing. Contrary to popular opinion, this swing is not produced by air flowing faster over the smooth or "shiny" side as compared to the rough side.

Swing is produced due to a net force acting on the ball from one side; that is, the side with the more turbulent boundary layer. For conventional swing bowling, the raised seam and the direction in which it is pointed governs the direction of swing. Due to the angled seam of the ball, air flowing over the seam produces turbulence on the side that the seam is angled toward. This causes the boundary layer to separate from the surface of the ball later (farther toward the rear of the ball) than the other side where it separates earlier (farther forward on the surface). As explained by Bernoulli's principle, there is a net pressure differential due to the greater pressure on the side with the more intact boundary layer. The resulting net force acts so as to move or swing the ball in the direction of the angled seam. Conventional swing bowling is delivered with the seam angled such that the smooth or polished side of the ball faces forward to move the ball in the direction of the seam i.e. toward the rough side.

A swinging ball is classed as either an outswinger, which moves away from the batsman, or an inswinger, which moves in toward the batsman. In most cases the outswinger is seen as the more dangerous ball because, if the batsman fails to recognise it, it will catch the outside edge of the bat instead of the middle and fly up to be caught in the slips. Inswingers have their place too, especially combined with the yorker as the inswinger can catch the inside edge and break the wicket, or hit the batter on the pad rather than the bat, resulting in a possible LBW decision.

Swing bowling can also be roughly categorised as early swing or late swing, corresponding to when in the trajectory the ball will change direction - the later the ball swings, the less chance the batter has of adjusting his/her shot to account for the swing.

Swing balls are bowled with the same grip and technique as fast balls although the seam is usually angled slightly rather than straight, and the slower ball grip may be used. For an outswinger the shiny side of the ball is nearest the batsman and the seam is angled away from him while for an inswinger, the rough side needs to be nearest the batsman and the seam angled toward them. It is difficult to achieve swing with a cutter grip since the ball will spin in flight, varying the orientation of the shiny and rough surfaces as it moves through the air. Many players, commentators on the game, and fans agree that swing is easier to achieve in humid or overcast conditions, and also that the red ball used in Test cricket swings more than the white ball used in the one-day game.