Study on Boundary-Layer Transition, Separation and Three-Dimensional Wake Structures post Knuckleball

Abstract

The irregular dynamic behavior of a knuckleball is believed to be caused by the seam and the asymmetrical flow separation. In the present experiment, the characteristic of the force acting on a baseball and the velocity vector fields in the wake were further correlated with the seam orientations of the baseball. The seam was identified to cause flow separation or boundary layer transition depending on its position. Hysteresis effect of the boundary layer separation as well as three-dimensional vortical wake structures were examined.