In the past three decades, the study of vortices and vortex mo-
motions - which originated in Helmholtz's great paper of 1858, 'Uber
lntegnile der hydrodynamischen Gleichungen welche den Wirbelbewegun-
gen eMsprechen' (translated by Tait [1867]), and continued in the brilliant
work of Lord Kelvin and others in the nineteenth century, and Prandtl
and h s Gottingen school in the first half of this century - has received
continiing impetus from problems arising in physics, engineering and math-
mathematics. As aptly remarked by Kiichemann A965J, vortices are the 'sinews
and muscles of fluid motions'. Aerodynamic problems of stability, control,
delta wing aerodynamics, high lift devices, the jumbo jet wake hazard phe-
nomeron, among other concerns, have led to a myriad of studies. Smith
[1986) reviews some of this work. The realisation that many problems
involv ng interfacial motion can be cast in the form of vortex sheet dynam-
dynamics ha: stimulated much interest. The discovery (rediscovery?) of coherent
structures in turbulence has fostered the hope that the study of vortices
will lead to models and an understanding of turbulent flow, thereby solving
or at least making less mysterious one of the great unsolved problems of
classical physics. Vortex dynamics is a natural paradigm for the field of
chaoti( motion and modern dynamical system theory. It is perhaps not well
known that the father of modern dynamics and chaos wrote a monograph
on vorticity (Poincare 11893J). The theory of line vortices and vortex rings
is a part of modern macroscopic treatments of liquid helium II, as is de-
describee by Donnelly and Roberts [1974], Even Kelvin's 11867a] vortex
theory of matter may one day have some topical interest.
Much of the modern work has been made possible by the remarkable