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Large eddy simulation of flow past a cricket ball with its seam at to the free stream is carried out for . Three regimes of flow are identified on the basis of the time-averaged swing force coefficient （ ） – no swing （NS）, conventional swing （CS, 0$]]> ） and reverse swing （RS, ）. The effect of seam on the boundary layer is investigated. Contrary to the popular belief, the boundary layer does not transition to a turbulent state in the initial stages of CS. The seam energizes the laminar boundary layer and delays its separation. The delay is significantly larger in a region near the poles, whose extent increases with an increase in causing to increase. Here assumes a near constant value in the later stage of CS. The boundary layer transitions to a turbulent state via formation of a laminar separation bubble （LSB） in the equatorial region and directly, without a LSB, in the polar region. The extent of the LSB shrinks while the region of direct transition near the poles increases with an increase in . A LSB forms on the non-seam side of the ball in the RS regime. A secondary vortex is observed in the wake bubble. While it exists on the non-seam side for the entire range of considered, the mixing in the flow introduced by the seam causes it to disappear beyond a certain on the seam side. The pressure difference between the seam and non-seam sides sets up wing-tip-like vortices. Their polarity reverses with the switch from the CS to RS regime.
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