It has been recognized by many investigators that vortex rings are  one of the most fundamental and fascinating phenomena in fluid  dynamics. They are both esthetically beautiful prevolent in the real

world . As stated by Philip Saffman : ‘One particular motion  exemplifies the whole range of problems of vortex motion and is  also a commonly known phenomenon, namely the vortex ring . . .  Their formation is a problem of vortex sheet dynamics, the steady  state is a problem of existence, their duration is a problem of  stability, and if there are several we have a problem of vortex  intractions’.

In our work we have focused on the dynamics of thin vortex rings.  In particular we have studied their formation, their speed of  propagation, drag and the influence of wave instabilities on the  speed of propagation. Additionally we have studied the shedding  of vortex ring by an oscillating sphere and the influence of these  on the decay of an oscillating object.

Below are a few videos that illustrate the beauty of these rings

Relevant Papers

D Bolster, R Herschberger and RJ Donnelly
Dynamic Similarity, the Dimensionless Science
Physics Today, Volume 64, Issue 9, P 42-47

D Bolster, R Herschberger and RJ Donnelly
An appreciation of the 1939 paper "On an experimentally observed phenomenon on vortex rings ..."by Carl-Heinz Krutzsch
Annalen der Physik, Volume 523, Issue 5, pages 380–382, May 2011

D Bolster, R Herschberger and RJ Donnelly
Translation of the 1939 paper "On an experimentally observed phenomenon on vortex rings ..."by Carl-Heinz Krutzsch
Annalen der Physik, Volume 523, Issue 5, pages 360–379, May 2011

RE Hershberger, D Bolster and RJ Donnelly
Slowing of vortex rings by development of Kelvin waves
Physical Review E, 82, 036309

D. Bolster, R.E. Hershberger and RJ Donnelly
Oscillating pendulum decay: Vortex ring induced drag, Physical Review E, 81, 046317, DOI: 10.1103/PhysRevE.81.046317

Sullivan IS, Niemela JJ, Hershberger R, Bolster D, Donnelly RJ (2008)
"Dynamics of Thin Vortex Rings"
Journal of Fluid Mechanics - Vol 609, 319-347