Low KC flow regimes of oscillating sharp edges, I: Vortex shedding observation.

Viscous flow around an oscillating vertical cylinder with a disk attached at keel is studied in detail by direct numerical simulation based on finite difference method. Over the range of flow parameters investigated, viz. Keulegan–Carpenter number (KC) from 7.5 x 10^ to 0.75 and b = 1.585 x 10^5; three shedding modes were observed. These modes, named independent, interactive and uni-directional, are found to be governed by both flow parameters (KC, b) and the geometry of the disk, such as aspect ratio, td/Dd: The mechanism for the initial condition dependence of the asymmetric uni-directional vortex shedding is analyzed. The effects of KC number and aspect ratio of the disk on the vortex shedding angle are also presented