Date of Award
Master of Science (MS)
John P. Borg
Philip A. Voglewede
There has been plenty of research on the fluid dynamic effects on different spheres, including sports balls, such as baseballs. Baseball pitches have different velocities, rotation rates and orientations which will cause the baseball to move in different directions. There has also been plenty of research on the aerodynamics of curveballs, but not nearly as much on knuckleballs. The difference between the two is that the knuckleball has a much slower rotation rate and a different initial orientation. This causes the baseball to "knuckle," or moving erratically. This pitch in baseball is one of the hardest to pitch, hit, catch, and umpire. So through various wind tunnel experiments, an attempt will be made that would predict the movement of the pitch under these given conditions.
The experimental data includes force balance dynamometry, flow visualization, and hot film anemometry. The force balance data includes the lift and lateral forces acting on a two-seam baseball rotating at 50 rpm. The flow visualization presents how separation on a rotating, two-seam baseball changes position along the surface of the ball due to rotation and the seams. Lastly, hot film anemometry illustrates how the seams effect separation during a rotation of the baseball. Together, these experiments illuminate the complicated interactions the presence of the seam induces, namely for formation of the turbulent boundary layer juxtaposed against the variations in the location of separated region.