Flow Characteristics around a Circular Cylinder with Grooves.

Abstract

In the flow around a circular cylinder, the sudden decrease in the drag force occurs at around Reynolds number Re=3×105, but the same phenomenon occurs at a lower Reynolds number in the case where there exist grooves or roughness on the circular cylinder surface. In this paper, in order to make clear the flow characteristics around a circular cylinder with grooves, the unsteady flow was analysed by applying the RNG (Renormalization Group) κ-e turbulent model to a flow around a circular cylinder with grooves each of whose section shapes being as same as that of a dimple on a golf ball, with changing Reynolds number. This result made clear the characteristics of lift and drag, Strouhal number, flow pattern behind the circular cylinder, pressure distribution and separation points. Moreover, the time averages of these values almost agreed with the experimental values.