Affiliations: Department of Mechanical Engineering, Kanagawa
Institute of Technology, 1030 Shimoogino, Atugi-shi, Kanagawa 243-0292, Japan.
E-mail: yamagisi@me.kanagawa-it.ac.jp | School of High-Technology for Human Welfare, Tokai
University, 317 Nishino, Numazu-shi, Shizuoka 410-0395, Japan
Abstract: In the flow around a circular cylinder, a sudden decrease in the
mean 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 mean drag coefficient, pressure distribution, velocity distribution and
turbulence intensity distribution were measured. Moreover, the flow around the
cylinder was analyzed by applying the RNG k - ε turbulent model, and the surface
flow pattern was investigated using the oil-film technique. From these results,
it was found that a sudden decrease in the mean drag coefficient of a cylinder
with 32 triangular grooves occurs at a lower Reynolds number compared with 20
and 26 triangular grooves.
