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The merger of two-dimensional radially stratified high-Froude-number vortices

Joly, Laurent and Reinaud, Jean The merger of two-dimensional radially stratified high-Froude-number vortices. (2007) Journal of Fluid Mechanics, vol. 5 . pp. 133-151. ISSN 0022-1120

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Official URL: http://dx.doi.org/10.1017/S0022112007005745

Abstract

We investigate the influence of density inhomogeneities on the merger of two corotating two-dimensional vortices at infinite Froude number. In this situation, buoyancy effects are negligible, yet density variations still affect the flow by pure inertial effects through the baroclinic torque. We first re-address the effects of a finite Reynolds number on the interaction between two identical Gaussian vortices. Then, by means of direct numerical simulations, we show that vortices transporting light fluid in a heavier counterpart merge from further distances than vortices in a uniform density medium. On the other hand, heavy vortices only merge from small separation distances. We measure the critical distance a/b0 of the vortex radii to their initial separation distance. It departs from the homogeneous threshold of 0.22 in response to increasing density contrasts between the vortices and their surroundings. An analysis of the contribution of the baroclinic vorticity to the dynamics of the flow is detailed and explains the observed behaviour. This analysis is completed by a simple model based on point vortices that mimics the flow. It is concluded that vortices carrying light fluid are more likely to generate large-scale structures than heavy ones in an inhomogeneous fluid.

Item Type:Article
Additional Information:Thanks to Cambridge University Press. The original PDF can be found on the Cambridge University Press website : http://journals.cambridge.org/action/displayJournal?jid=FLM
Audience (journal):International peer-reviewed journal
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Institution: Université de Toulouse > Institut Supérieur de l'Aéronautique et de l'Espace - ISAE
Other partners > University of St Andrews (UNITED KINGDOM)
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Deposited By:Laurent JOLY

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