CFD Analysis of swing of cricket ball and trajectory prediction

Josin Tom, Jithin G, Kamat Ruishikesh
National Institute of Technology Calicut

The primary objective of the work was to understand the mechanism and aerodynamics associated with the flight and swing of a cricket ball and use this to predict its flight trajectory over the course of the game: at start (smooth ball) and as the game progresses (rough ball). Asymmetric airflow over the ball due to seam orientation and surface roughness of the ball can cause flight deviation (swing), which makes it difficult for the batsman to hit the ball or guard his stumps. The values of coefficients of Drag(CD), Lift(CL) and Side force(CS) which are crucial for determining the trajectory of the ball were found with the help of FLUENT using the standard K-ϵ model. Seam imposed sphere with smooth surfaces equivalent to a new ball was simulated first. Next, sinusoidal projections were created on one surface to simulate the old ball which is rough on one side. Analysis was done to study how the ball velocity, spin imparted to be ball and the tilt of the seam affects the movement of the ball through air. Laws of mechanics were used to derive the governing force balance equations in 3 dimensions for a trajectory acted upon by gravity, drag, lift and side force. The values of force coefficients obtained in FLUENT was given as an input to the MATLAB code which used Heun’s method for solution of trajectory equations and plotted the trajectory of the ball. The conditions for the conventional swing and reverse swing to occur were deduced from the analysis and found to be in alignment with the real life situation. The drag coefficient of the ball was deduced. Critical seam angle for maximum swing and transition speed for normal to reverse swing were found out. The obtained trajectories were compared to real life hawk eye trajectories for validation. The analysis results were in good agreement with the real life situation.