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dc.contributor.authorReinaud, Jean Noel
dc.contributor.authorDritschel, David Gerard
dc.identifier.citationReinaud , J N & Dritschel , D G 2002 , ' The merger of vertically offset quasi-geostrophic vortices ' , Journal of Fluid Mechanics , vol. 469 , pp. 287-315 .
dc.identifier.otherPURE: 174961
dc.identifier.otherPURE UUID: 02e1ffb1-36c7-4bcd-a1be-ca195363f630
dc.identifier.otherWOS: 000178965700012
dc.identifier.otherScopus: 0037174889
dc.identifier.otherORCID: /0000-0001-5449-6628/work/34852210
dc.identifier.otherORCID: /0000-0001-6489-3395/work/64697810
dc.description.abstractWe examine the critical merging distance between two equal-volume, equal-potential-vorticity quasi-geostrophic vortices. We focus on how this distance depends on the vertical offset between the two vortices, each having a unit mean height-to-width aspect ratio. The vertical direction is special in the quasi-geostrophic model (used to capture the leading-order dynamical features of stably stratified and rapidly rotating geophysical flows) since vertical advection is absent. Nevertheless vortex merger may still occur by horizontal advection. In this paper, we first investigate the equilibrium states for the two vortices as a function of their vertical and horizontal separation. We examine their basic properties together with their linear stability. These findings are next compared to numerical simulations of the nonlinear evolution of two spheres of potential vorticity. Three different regimes of interaction are identified, depending on the vertical offset. For a small offset, the interaction differs little from the case when the two vortices are horizontally aligned. On the other hand, when the vertical offset is comparable to the mean vortex radius, strong interaction occurs for greater horizontal gaps than in the horizontally aligned case, and therefore at significantly greater full separation distances. This perhaps surprising result is consistent with the linear stability analysis and appears to be a consequence of the anisotropy of the quasi-geostrophic equations. Finally, for large vertical offsets, vortex merger results in the formation of a metastable tilted dumbbell vortex.
dc.relation.ispartofJournal of Fluid Mechanicsen
dc.rights(c)2002 Cambridge University Pressen
dc.subjectVortex Dynamicsen
dc.subjectQA Mathematicsen
dc.titleThe merger of vertically offset quasi-geostrophic vorticesen
dc.typeJournal articleen
dc.description.versionPublisher PDFen
dc.contributor.institutionUniversity of St Andrews. Applied Mathematicsen
dc.description.statusPeer revieweden

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