1. Fig.2 Boundary Separation contributing to Swing
The Fast Bowler
To obtain conventional swing as a fast bowler
 The ball is released with the seam at
an angle to the initial line of flight.
 Over a certain Reynolds number
range (>65mph), the seam trips the
laminar boundary layer into
turbulence (Fig. 2) on one side of the
ball.
 Whereas on the other (non-seam)
side remains laminar (Fig. 2).
 By virtue of its increased energy, the
turbulent boundary layer, separates
later (further back along the ball
surface) compared to the laminar
layer and so a pressure differential,
which results in a side force, which
makes the ball deviate from its line of
path i.e. swing.
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A Practitioner Information leaflet on Fluid
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CRICKET
THE BOWLERS EDGE
The Impact of Science on
Bowling.
Fluid Dynamics, flow and
Streamlining in Cricket
CRICKET
THE
BOWLERS
EDGEThe Impact of Science on
Bowling
Fluid Dynamics, Flow and
Streamlining in Cricket

2. The Impact of Science
on Bowling.
“the beauty of this sport lies
when the bowler and the
batsman try to dominate each
other for supremacy”
Getting the Edge:
There are five main components in
determining a cricket balls flight path:
1. Seam Angle
2. Velocity (Reynolds Number)
3. Drag (Surface Friction)
4. Boundary Separation
5. Spin Rate (Magnus Force)
There are two vital phases during the
delivery a bowled cricket ball.
Phase 1: The ball undergoes free flight from
the point it is released from the bowler’s hand
until it hits the crease. During this phase the
motion of the ball is entirely under the
influence of aerodynamic forces and the
bowler is capable of controlling its motion to a
considerable extent.
Phase 2: Involves the travel of the ball
towards the batsman after bouncing off the
crease. During this phase the motion of the ball
is basically governed by the orientation of the
ball when it bounces off the crease and the
condition of the crease and hence the bowler
has less control on the ball.
The aerodynamics of a cricket ball
depend on two possible states of the
outer layer (boundary layer).
Laminar - in which the flow is regular, smooth
and barely parallel to the surface.
Turbulent - where the general average motion
is roughly parallel to the surface but there are
rapid random fluctuations in velocity,
direction and magnitude.
Fig.1 Magnus Effect Spin Bowling
The Spin Bowler
To obtain conventional spin as a spin bowler
 When spin is about the seam of the
ball.
 The ball bores through the air like a
drill.
 Creating low pressure on the top
and high on the bottom. Creating
uplift. (Fig.1)
 Because of symmetry on each side of
the seam, no lateral force will be
generated.
 Spin can also take place about any
other inclined axis passing through
the center of the ball.
 Height, distance and curve of the ball
will be dictated by the amount of
rotational forces applied by the
bowler to the ball i.e. spin.