Abstract
In the flow around a circular cylinder, a sudden decrease in the drag coefficient occurs at a high Reynolds number, but the same phenomenon occurs at a lower Reynolds number in the case where there exist grooves or roughness on the cylinder surface. In this paper, in order to make clear the flow characteristics around a cylinder with 20, 26 and 32 triangular grooves, the drag coefficient, pressure, velocity and turbulence intensity distributions were measured. Moreover, the flow around the cylinder was analyzed by applying the RNG k-ε turbulent model, and the surface flow pattern was observed using the oil-film technique.
