The influence of seam orientation on the lift and drag of a rotating baseball in flight

Abstract

The effect of seam orientation relative to the spin axis on the forces of a rotating baseball has been studied, and debated, for as long as baseball has existed. Early debates centered on whether a spinning baseball could even curve and eventually changed to whether the orientation of seams had any impact on the forces acting on the ball during flight. This study uses Computational Fluid Dynamics to show that the seam orientation can have a significant influence on the lift force experienced by a baseball in flight, but that influence diminishes as the rate of spin approaches the natural shedding frequency of a sphere of the same size. Oscillations in the wake caused by the passing of seams across the upper and lower surface eventually give way to larger scale instabilities and the impact of seam orientation on the forces acting on the ball is significantly reduced.