Flow Characteristics for Grooves' Depth of a Circular Cylinder with Grooves

概要

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Flow around a cylinder in a uniform flow shows different features depending on the Reynolds number. Among them, the sudden decrease in the drag force at a certain Reynolds number is well known. While the decrease occurs usually at around Re3×10^5,it is also observed at a Reynolds number lower than this value for the case of cylinder which have the surface of grooves or roughness. The latter is practically applied to dimples of golf ball, grooves of low wind pressure cable, pipe jumpers covering cables, and so on. The flying distance of a golf ball is increased by the dimples, and the drag force acting on the cable can be decreased due to the effect of the grooves on a low wind pressure cable and pipe jumper. In the present study, in order to understand the effect of the groove on the flow of a cylinder, an unsteady flow analysis was carried out using a turbulent model. The cylinder has grooves of the same sectional shape as that of a dimple on a golf ball. At different groove depths and Reynolds numbers, the flow features are calculated of lift and drag, Strouhal number, flow pattern behind the cylinder, pressure distribution and separation points. It is found that the time averages of these values almost agree with the experimental values.
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