On the relationship between the vortex formation process and cylinder wake vortex patterns

The idea of vortex formation time, originally developed for vortex ring formation, is extended to bluff-body flows. Effects related to characteristic vortex formation time are shown for both the cylinder starting from rest and the cylinder undergoing forced oscillations in a steady flow. By looking at how wake vortices are formed when the cylinder is accelerated from rest, it is found that similarities exist between the formation process for wakes and for vortex rings. This formation process is then observed for forced oscillating cylinders, where the characteristic formation time interacts with the oscillation period. Frequently observed bluff-body phenomena will be recast in light of the vortex formation process.