AERODYNAMICS OF BASEBALL

Aerodynamics of a baseball was investigated by both Computational Fluid Dynamics (CFD) and experimental trajectory analysis. Aerodynamic drag coefficients of the ball whose rotation axis direction is corresponding with ball's moving direction, which is called gyro ball, were calculated using CFD in two cases: two seam rotation and four seam one. The results showed drag coefficient of 4-seam rotation is about half of the drag coefficient of Zseam rotation. We performed experimental study using trajectory tracking by high speed video to estimate aerodynamic coefficients. We found two-seam and four-seam rotation balls showed different characteristics in drag coefficient when Reynolds number increased and both drag coefficients differ in Reynolds number 0.8 - 1.8 x l0 5exponent and spin parameter 0.1 2-0.23