Laser-sheet flow visualization on the wake behind a confined ring

Flow over a ring model situated axisymmetrically in a circular pipe has been studied by laser-sheet flow visualization technique. Over 25 cases of rings in different sizes were investigated and flow characteristics observed are summarized into six regimes, in reference to two geometrical parameters of G/W and D/W. Here, W is the width of the ring, D is the mean diameter of the ring, and G is the gap width between the pipe wall and the outer edge of the ring. It is interesting to point out that vortex-shedding structures produced by a ring model can exist a considerable distance downstream in three of the six regimes, which correspond to different physical processes of shedding. (A)