Computational study of influences of a seam line of a ball for baseball on flows

Abstract

Flows around a ball used in baseball games are calculated using third-order upwinddifference method with various seam positions determined by two rotation angles. Those are four-seam rotation with an angle: a and two-seam rotation with an angle: b. The computed results of the four-seam rotation are compared with experimental data measured in a wind tunnel and computed drag coefficients qualitatively agree well with experiments. However, lift coefficients do not agree well. The computed results and geometrical symmetry suggest that a supporting rod in the wind tunnel would have strong influence on the accuracy ofthe measurement.Flow changes in two-seam rotation are also simulated. It is found that the lowest drag force is observed at b=90 and that the value is less than half ofthe largest drag force at a=30 and 60 degrees. The largest lift force is observed at b=20 degree. In this case, a projection of the seam line on the top causes a large separation while smooth surface without the seam at the bottom dose not separate the flow. A pair of longitudinal vortices are found in the wake, which make wake slant and generate large lift force.

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

“…Together with the visualizations at intermediate angles, the boundary layer behavior is discussed more in detail in the next section. Recently, a numerical simulation to compute the behavior of the flow over a baseball has shown the threedimensional nature of boundary layer separation (Himeno, 2001), but the flow transition and/or flow separation at specific ball orientations as identified in this paper are not demonstrated.…”

“…At this rotational speed, the boundary layer on the surface is affected by the seams, and the wake generated over the baseball is deflected by the asymmetric boundary layer separation. Some aerodynamic measurements have been reported in the past (Mizota et al, 1995a,b;Watts and Sawyer, 1975) as well as numerical simulation of the flow (Himeno, 2001). However, the flow physics of the knuckleball, and in particular the boundary layer and separated flow characteristics, have not been documented.…”

Sports ball aerodynamics: A numerical study of the erratic motion of soccer balls

“…3D qualitative CFD analysis was carried out on a non-spinning cricket ball for both laminar and turbulent flow (using ANSYS FLOTRAN with the standard k-ε turbulence model) by Penrose et al [6] and on a rotating baseball (using an in-house code for the laminar regime only) by Himeno [7].…”

Optimization and Improvement of Throwing Performance in Baseball Pitching Machine Using Finite Element Analysis

“…The analysis was intended to start from the time the ball was thrown to just after release. Also, the flight trajectory of the ball after release was not considered (Watts et al, 1975, Himeno, 2001. …”