Influence of dimple design on aerodynamic drag of Golf balls

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Golf ball aerodynamics is significantly multifaceted as compared to other sports balls due to the presence of small dimples, which serve as a source of surface roughness and drag reduction. Overall aerodynamic performance of a golf ball is influenced by flow behavior over these dimples. Consequently, flow phenomena over the dimples is effected by various dimple characteristics, of which dimples geometry, size, shape, depth, and pattern are considered significant. Dimple characteristics continue to be an active area of research because the results thereof, affect the assertions, sales, and the performance of different commercially available golf balls. Dimples on the other hand also enhance the intricacy of flow over a golf ball; and due to this fact aerodynamics of a golf ball is yet to be fully recognized despite of considerable amount of available literature. Previous studies focused on overall aerodynamic performance of the golf ball through experimental analysis and Computational Fluid Dynamics (CFD) simulations; however, available literature still lacks detailed analysis of pertinent dimple characteristics. In this paper, dimple depth effect on the drag performance of a golf ball has been examined by employing numerical simulations, followed by validation through bench mark wind tunnel results of F. Alam (Procedia-2011). CFD simulations in ANSYS Fluent ® have been carried out for 5 balls with varied dimple depth over various velocities (wind). It has been established that golf ball drag coefficient varies considerably as the dimple geometry is varied. The results specify a direct relationship between dimple depth ratio and transitioning Reynolds number. As the depth ratio is increased the transitioning Reynolds number is lowered and this also serves to increase the drag coefficient in transcritical regime. A positive linear relationship was also established between coefficient of drag and relative roughness.