The propagation and decay of a coastal vortex on a shelf

A coastal eddy is modelled as a barotropic vortex propagating along a coastal shelf. If the vortex speed matches the phase speed of any coastal trapped shelf wave modes, a shelf wave wake is generated leading to a flux of energy from the vortex into the wave field. Using a simple shelf geometry, we...

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Bibliographic Details
Published in:Journal of fluid mechanics 2021-11, Vol.927, Article A38
Main Authors: Crowe, Matthew N., Johnson, Edward R.
Format: Article
Language:English
Subjects:
Barotropic mode
Energy
Energy transfer
Fluctuations
JFM Papers
Mathematical models
Phase velocity
Self-similarity
Shelf waves
Shelves
Topography
Velocity
Vortices
Wave energy
Wave power
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Summary:A coastal eddy is modelled as a barotropic vortex propagating along a coastal shelf. If the vortex speed matches the phase speed of any coastal trapped shelf wave modes, a shelf wave wake is generated leading to a flux of energy from the vortex into the wave field. Using a simple shelf geometry, we determine analytic expressions for the wave wake and the leading-order flux of wave energy. By considering the balance of energy between the vortex and wave field, this energy flux is then used to make analytic predictions for the evolution of the vortex speed and radius under the assumption that the vortex structure remains self-similar. These predictions are examined in the asymptotic limit of small rotation rate and shelf slope and tested against numerical simulations. If the vortex speed does not match the phase speed of any shelf wave, steady vortex solutions are expected to exist. We present a numerical approach for finding these nonlinear solutions and examine the parameter dependence of their structure.
ISSN:0022-1120
1469-7645
DOI:10.1017/jfm.2021.790