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Session: PIV/PTV methods and applications IV
Session starts: Thursday 06 November, 11:00
Presentation starts: 11:40
Room: Lecture room A

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Shinichiro Ito (Bio & Sports Fluid Mechanics Laboratory)

Abstract:
Tennis balls are composed of a hard rubber core covered with a uniform felt fabric. Repeated impacts during gameplay cause the felt to wear and air to leak, resulting in changes to the aerodynamic properties of the ball. While new balls are used in official games, amateur practice often involves worn balls, which influence flight trajectories due to altered aerodynamic characteristics. Additionally, tennis balls frequently spin during flight and are not always used in pristine condition, prompting a study on the differences between new and worn spinning balls. Key findings include: (1) Minimal differences in fluid forces between official models XT8 and FORT for new balls; (2) Lift coefficient proportional to spin parameter (Sp) for both ball types; (3) Worn XT8 balls showed little change in drag coefficient but a decrease in lift coefficient; (4) Worn FORT balls exhibited increases in both drag and lift coefficients; (5) Wake pattern differences observed through Particle Image Velocimetry (PIV), attributed to variations in felt fluff texture. These results highlight the impact of felt wear on the aerodynamic performance of tennis balls, providing insights into how ball conditions influence gameplay and flight dynamics.