Effects of Shapes of Dimple on Flow Characteristics around a Golf Ball

It is known that the aerodynamic characteristics of the three dimensional bluff body such as a sphere depends on the surface structure. The purpose of this study is to clarify the mechanism of the drag reduction to the surface structural change. In this study, Reynolds number is changed from 4.23 × 10 4 to 1.69 × 10 5 . The diameter of the test sphere is 42.6 mm. The number of dimples is 328. The shapes of dimple are arc, cone and trapezoid. The state of the test sphere is stationary. The drag acting of the test sphere is measured using a three components loadcell. The pressure acting around the test sphere is measured using a pressure transducer. And more, the flow visualization around the test sphere is performed applying the spark tracing method. In addition, a detailed flow around the test sphere is clarified by the turbulent flow model LES. As a result of these experiments and numerical analysis, the drag coefficient for the shape of dimple, pressure coefficient, skin friction coefficient, separation point and the flow pattern around the test sphere became clear.