円柱伴流の渦列内の渦融合

抄録

The mechanism of rearrangement of the vortex street in the wake behind a circular cylinder at low Reynolds numbers was investigated in a low speed wind tunnel. The pairing of two vortices in the streamwise vortex rows of the so-called Kármán vortex street took place downstream of the primary vortex street of regular arrangement at Reynolds numbers lower than about 160. As the result of the vortex pairing, the secondary vortex street was generated further downstream. The streamwise variation of the wave forms in the wake was shown to correspond to that in the arrangement of the vortices in the visualized flow patterns in the transition region from the primary to the secondary vortex street. The width of the wake increased in the downstream direction, and the wake became increasingly wider with merging of vortices. The spacing ratio of vortices both in the primary and the secondary street had a value of 0.45 when they have fully developed.