Author:
SHUSSER MICHAEL,GHARIB MORTEZA
Abstract
Vortex ring formation in a starting axisymmetric buoyant plume is considered. A
model describing the process is proposed and a physical explanation based on the
Kelvin–Benjamin variational principle for steady vortex rings is provided. It is shown
that Lundgren et al.'s (1992) time scale, the ratio of the velocity of a buoyant plume
after it has travelled one diameter to its diameter, is equivalent to the time scale
(formation time) proposed by Gharib et al. (1998) for uniform-density vortex rings
generated with a piston/cylinder arrangement. It is also shown that, similarly to
piston-generated vortex rings (Gharib et al. 1998), the buoyant vortex ring pinches
off from the plume when the latter can no longer provide the energy required for
steady vortex ring existence. The dimensionless time of the pinch-off (the formation
number) can be reasonably well predicted by assuming that at pinch-of the vortex
ring propagation velocity exceeds the plume velocity. The predictions of the model
are compared with available experimental results.
Publisher
Cambridge University Press (CUP)
Subject
Mechanical Engineering,Mechanics of Materials,Condensed Matter Physics
Cited by
38 articles.
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