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Aerodynamics of sports ballsResearch data on the aerodynamic behavior of baseballs and cricket and golf balls are summarized. Cricket balls and baseballs are roughly the same size and mass but have different stitch patterns. Both are thrown to follow paths that avoid a batter's swing, paths that can curve if aerodynamic forces on the balls' surfaces are asymmetric. Smoke tracer wind tunnel tests and pressure taps have revealed that the unbalanced side forces are induced by tripping the boundary layer on the seam side and producing turbulence. More particularly, the greater pressures are perpendicular to the seam plane and only appear when the balls travel at velocities high enough so that the roughness length matches the seam heigh. The side forces, once tripped, will increase with spin velocity up to a cut-off point. The enhanced lift coefficient is produced by the Magnus effect. The more complex stitching on a baseball permits greater variations in the flight path curve and, in the case of a knuckleball, the unsteady flow effects. For golf balls, the dimples trip the boundary layer and the high spin rate produces a lift coefficient maximum of 0.5, compared to a baseball's maximum of 0.3. Thus, a golf ball travels far enough for gravitational forces to become important.
Document ID
19850049027
Acquisition Source
Legacy CDMS
Document Type
Conference Proceedings
Authors
Mehta, R. D.
(NASA Ames Research Center Aerodynamics Research Branch, Moffett Field, CA; Stanford University, Stanford, CA, United States)
Date Acquired
August 12, 2013
Publication Date
January 1, 1985
Subject Category
Fluid Mechanics And Heat Transfer
Accession Number
85A31178
Distribution Limits
Public
Copyright
Other

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