Session Ce - Separated Flows.
ORAL session, Sunday, November 23
305, Moscone Center
We conducted several experiments on ramp-started circular cylinders. The flow field was measured using Digital Particle Image Velocimetry (DPIV), which allowed us to observe the growth of circulation with time in the wake of the cylinder. Following Rambod, et. al. (JFM, 1997) we measured the "formation number" of this flow, which coincidentally was also four diameters. The formation number is the non-dimensional time at which the vortices reach the circulation that is eventually shed; in effect, the time scale for vortex formation. At low acceleration this number was very different from four, and in fact the vortex shedding behavior was qualitatively different. >From the evolving vorticity field we can illustrate these two behaviors.