円板後流における大規模渦構造の特性

抄録

The vortex structures in the wake behind a circular disk, as a representative bluff body, were investigated by PIV measurement. Stereo PIV results perpendicular to the mainstream direction were visualized in the iso-surface of Q-criterion reconstructed three-dimensional vortex structure. It was found that the vortex structure at Re = 650 has a feature of staggered-type I with small vortices. In addition, velocity fluctuations in the wake behind a circular disk were decomposed into various scale structures by phase-averaged technique. The large-scale structures in the wake of circular disk were shown as alternatingly a series of connecting hairpin vortices. Small-scale structures revealed regular small vortices between adjacent hairpin vortices. Furthermore, we investigated the formation mechanism of the staggered-type I in the wake. When the vortices were separated, recirculation region was split into two vortex structures. One of those structure flowed downstream, rolled up as a vortex. The other went upstream, generating counter-rotating vortex with another recirculation region.