  Buoyancy produced by autocatalytic reaction fronts can produce fluid flows
that advect the front position, giving rise to interesting feedback between
chemical and hydrodynamic effects. In a large diameter, extended cylinder that
is relatively free of boundary constraints, localized initiation of an
iodate-arsenous acid (IAA) reaction front on the bottom boundary generates a
rising autocatalytic plume. Such plumes have several differences from their
non-reactive counterparts. Using numerical simulation, we have found that if
reaction is initiated using a spherical ball of product solution well above the
bottom boundary, the subsequent flow can evolve much like an autocatalytic
plume: the ball develops a reacting head and tail that is akin to the head and
conduit of an autocatalytic plume, except that the tail is disconnected from
the boundary. In the limit of large initial autocatalytic balls, however,
growth of a reacting tail is suppressed and the resemblance to plumes
disappears. Conversely, very small balls of product solution fail to initiate
sustained fronts and eventually disappear.
