High resolution DPIV measurements are made of a vortex ring formed by
a piston/cylinder mechanism (Reynolds number 3700 and 7500). A complex
ring structure is identified. The stopping condition of the piston le
ads to vortical fluid collecting near the forward stagnation point of
the ring. In addition, the roll-up of the core produces a vorticity di
stribution that departs from a simple Gaussian profile. (C) 1997 Ameri
can Institute of Physics.