Aerodynamic principles affect the flight of a sports ball as it travels through the air. From the design of dimples on a golf ball or the curved flight path of a tennis, cricket or baseball, aerodynamics affects speed, motion (position and placement) and ultimately athletic performance. The aerodynamics of several different sports balls, including baseballs, golf balls, tennis balls, cricket balls, volleyballs and soccer balls are discussed with the help of recent wind tunnel measurements and

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... eoretical analyses. An overview of basic sports ball aerodynamics as well as some new flow visualization data and aerodynamic force measurements are presented and discussed. The materials include explanations of basic fluid dynamics principles, such as Bernoulli's theorem, circulation, the four flow regimes a sphere or a sports ball encounters, and laminar and turbulent boundary layers. The effects of these specific mechanisms on the behavior and performance of sports balls are demonstrated. The specific aerodynamics of the strategic pitches, serves, kicks and strokes used in each sport are described. In particular, the effects of surface roughness and spin on the behavior of the boundary layers and the critical Reynolds number are discussed here. For spinning balls, the Magnus effect, which is responsible for producing the side or lift force, is discussed in detail, as well as the conditions under which a negative or reverse Magnus effect can be created. It is interesting to note that except for golf and cricket, the ball in all the other games included in the present discussion undergoes a flight regime when the ball is not spinning. The role of the surface roughness, especially if it can be used to generate an asymmetric flow, becomes even more critical for these cases. This paper compares and contrasts the unique aerodynamic characteristics of a variety of sports balls.