Author:
CARNEVALE G. F.,BRISCOLIN M.,KLOOSTERZIEL R. C.,VALLIS G. K.
Abstract
Numerical experiments are used to study the evolution of perturbed
vortex tubes in a
rotating environment in order to better understand the process of
two-dimensionalization of unsteady rotating flows. We specifically
consider non-axisymmetric perturbations to columnar vortices aligned
along the axis of rotation. The basic unperturbed
vortex is chosen to have a Gaussian cross-sectional vorticity distribution.
The experiments cover a parameter space in which both the strength of the
initial perturbation
and the Rossby number are varied. The Rossby number is defined here as
the ratio of
the maximum amplitude of vorticity in the Gaussian vorticity profile to
twice
the ambient rotation rate. For small perturbations and small Rossby numbers,
both cyclones
and anticyclones behave similarly, relaxing rapidly back toward two-dimensional
columnar vortices. For large perturbations and small Rossby numbers, a
rapid
instability occurs for both cyclones and anticyclones in which antiparallel
vorticity is
created. The tubes break up and then re-form again into columnar vortices
parallel to
the rotation axis (i.e. into a quasi-two-dimensional flow) through
nonlinear processes.
For Rossby numbers greater than 1, even small perturbations result in the
complete
breakdown of the anticyclonic vortex through centrifugal instability, while
cyclones
remain stable. For a range of Rossby numbers greater than 1, after the
breakdown
of the anticyclone, a new weaker anticyclone forms, with a small-scale
background
vorticity of spectral shape given approximately by the −5/3 energy
spectral law.
Publisher
Cambridge University Press (CUP)
Subject
Mechanical Engineering,Mechanics of Materials,Condensed Matter Physics
Cited by
27 articles.
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