Aerodynamics of knuckle ball: Flow-structure interaction problem on a pitched baseball without spin

On the Aerodynamic Forces on a Baseball, With Applications

“…Experiments by Higuchi and Kiura [38] show that a variation of only one degree (36 to 37 • ) in the stitch position causes a sudden separation. Moreover, they reported that the balls are more susceptible to hysteresis (including induced rotation) at the zones of separation.…”

“…Investigations carried out in the present decade show structured oscillations of drag coefficient despite the turbulence present in the phenomenon. For example, the experiment by Higuchi and Kiura [38] with different configurations of the ball, namely, the four-seam (4S), the twoseam (2S) and an arbitrary orientation of the ball 1 . They found the largest variation in oscillations for the 4S orientation, which is about twice as large as the case of the 2S orientation and around four times that of the arbitrary orientation.…”

Aerodynamics of the knuckleball pitch: Experimental measurements on slowly rotating baseballs

“…1 Thus, the aerodynamically induced motion of sports balls has long been a subject of interest to players and physicists alike. [2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19] Pitchers take advantage of these effects with an arsenal of different breaking pitches: sliders and curveballs, sinkers, cutters, and the ever-confounding knuckleball. Each pitch is delivered with aerodynamics in mind, from the way the pitcher grips the ball and aligns the seams, to the initial velocity, spin, and axis of rotation.…”

“…Figure 3 presents the averaged dimensionless lift from a non-spinning ball in a 4S orientation as a function of ball angle at a Reynolds number of 1.6 Â 10 5 . The data of Watts and Sawyer 7 and Higuchi and Kiura 19 are presented for comparison. Pictures illustrating the seam locations for corresponding ball angles are displayed directly below the x-axis for reference.…”

“…D. Force measurements: Two-seam (2S) orientation Figure 5 presents the lateral and lift force for a nonspinning baseball in a 2S orientation obtained at a Reynolds number of 1.6 Â 10 5 . Included on this figure are data obtained from Higuchi and Kiura 19 and a pitch window, illustrated as a shaded region from 120 to 300 , which represents the desired ball rotation of Dickey and Wakefield. 22,23 The lift and lateral force data for the 2S pitch contain much more structure compared to the 4S pitch.…”