Vortex methods have become useful tools for
the computation of incompressible flows in which vorticity is an
important component. The essence of these methods is a
computational element---or particle---that carries
vorticity and is convected by the flow. Each vortex element, or
'particle', has a corresponding velocity distribution. The
instantaneous velocity field
is the composition of all particles' contributions, dependent on their
strengths
and positions. These methods are often preferrable to traditional
fixed-grid
schemes in their economy of computational elements (only where
vorticity
is present) and their ability to handle more complicated
geometries. Some simple examples that demonstrate the utility of
the
method are presented in the following movies (double-click to start, need QuickTime plugin):