Vortex Formation from a Cylinder Moving Through a Free-Surface

Vortex formation from a cylinder moving through a free-surface.  The initial phase of development of pairs of vortices from a cylinder occurs when it moves from its extreme position (maximum submergence), corresponding to phase angle phi = 0°, towards the free surface located at nu* = nu/D = 0. Vortices A and B, which are initially formed during the downstroke, induce very rapid separation from the surface, leading to formation of vortices C and D during the upstroke. The equilibrium position of the cylinder is at h* = h/D = 1.6. Minimum and incremental values of vorticity are the same for these and all subsequent images.