Abstract
This study eluidates the onset of wake oscillation and the generation process of the oscillating bubble behind a circular cylinder by visualizing computed results obtained by solving numerically the two-dimensional, time-dependent Navi-er-Stokes equations at the low Reynolds numbers. The zero-streamline begins to oscillate near the rear stagnant point at Re=1-4. A bubble composed of two standing vortices adhered to the cylinder certainly begins to oscillate at Re=5.60-5.6 2. Instability generated by motion of the zero-streamline and the bubble is not transported into the downstream and is the absolute instability, since the flow outside the neighborhood of the rear stagnnant point is completely steady and symmetric at Re≤16.
