The shape of vortices in quasi-geostrophic turbulence
Date
10/01/2003Metadata
Show full item recordAbstract
The present work discusses the most commonly occurring shape of the coherent vortical structures in rapidly rotating stably stratified turbulence, under the quasi-geostrophic approximation. In decaying turbulence, these vortices-coherent regions of the materially-invariant potential vorticity-dominate the flow evolution, and indeed the flow evolution is governed by their interactions. An analysis of several exceptionally high-resolution simulations of quasi-geostrophic turbulence is performed. The results indicate that the population of vortices exhibits a mean height-to-width aspect ratio less than unity, in fact close to 0.8. This finding is justified here by a simple model, in which vortices are taken to be ellipsoids of uniform potential vorticity. The model focuses on steady ellipsoids within a uniform background strain flow. This background flow approximates the effects of surrounding vortices in a turbulent flow on a given vortex. It is argued that the vortices which are able to withstand the highest levels of strain are those most likely to be found in the actual turbulent flow. Our calculations confirm that the optimal height-to-width aspect ratio is close to 0.8 for a wide range of background straining flows.
Citation
Reinaud , J N , Dritschel , D G & Koudella , CR 2003 , ' The shape of vortices in quasi-geostrophic turbulence ' , Journal of Fluid Mechanics , vol. 474 , pp. 175-192 . https://doi.org/10.1017/S0022112002002719
Publication
Journal of Fluid Mechanics
Status
Peer reviewed
ISSN
0022-1120Type
Journal article
Rights
(c)2003 Cambridge University Press
Description
Partially supported by the UK EPSRC (Grant GR/N11711)Collections
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