Abstract
The oscillation behavior of the necklace vortices formed in front of a square flat plate protuberance standing vertical to the laminar boundary layer flow on the ground wall was investigated by using a moving path line method and a time successive PIV method. The necklace vortex system consisting of eight vortices with the extremely small oscillation appears around the square plate with h/δ=2 at Reynolds number Re=1760. The oscillation with a cycle of five seconds is clearly observed for the eight vortices at Re=2040. The center vorticity of main vortex V1 seems to take the maximum value at about Re=1700, and reduces as the Reynolds number increases beyond 1700.
