The physics of vortex merger: Further insight

Structure formation and self-organization in two-dimensional drift-wave turbulence show up in many different faces. Fluctuation data from a magnetized plasma are analyzed and three mechanisms transferring kinetic energy to large-scale structures are identified. Beside the common vortex merger, clustering of vortices constituting a large-scale strain field and vortex thinning, where due to the interactions of vortices of different scales larger vortices are amplified by the smaller ones, are observed. The vortex thinning mechanism appears to be the most efficient one to generate large scale structures in drift-wave turbulence. Vortex merging as well as vortex clustering are accompanied by strong energy transfer to small-scale noncoherent fluctuations (dissipation) balancing the negative entropy generation due to the self-organization process.

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“…This definition is in line with the definitions in Refs. [17][18][19]. It should not be confused with the definition the blob community [20] use.…”

Section: Coherent and Noncoherent Structuresmentioning

confidence: 99%

A link between nonlinear self-organization and dissipation in drift-wave turbulence

Mänz¹,

Birkenmeier

Ramisch

et al. 2012

Physics of Plasmas

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“…For this reason, a number of studies have been devoted to the understanding of the key mechanisms of this process. [3][4][5][6][7][8] Previous experimental and numerical studies 3,[9][10][11][12][13][14][15] have shown that two identical vortices merge if their initial intercentroid distance is smaller than some critical value, leading to a vortex larger in size than the original vortices. It was also shown that the interaction of unequal corotating vortices is much richer than that of equal vortices.…”

Section: Introductionmentioning

confidence: 99%

Dynamics of two identical vortices in linear shear

2010

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The dynamics of two identical vortices in linear shear was studied both numerically and experimentally. Numerical simulations based on the technique of contour dynamics reveal that the vortex evolution in adverse shear is significantly different from that in cooperative shear. Vortices in adverse shear predominantly separate, whereas vortices in cooperative shear predominantly merge. In addition, adverse shear may destruct the vortices much in the same way as a single vortex in adverse shear, whereas cooperative shear stabilizes the vortices and thus enhances the possibility of vortex merger. The critical distance for vortex merger depends strongly on both the sign and the strength of the linear shear and, to a lesser extent, on the initial vorticity distribution. A simple vortex merger criterion is derived based on the interaction of two point vortices in linear shear. The different behavior of vortices in adverse and cooperative shear was confirmed by rotating-tank experiments.

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“…However, in the vicinity of the hyperbolic points, and in particular the central hyperbolic (CH) point where mutual interaction strengthens ∇ω amplification (Fig. 2-light shading near center is P s > 0), the dynamics of ∇ω and S eventually produces a tilt in ω contours [1]. At the outer hyperbolic points, this initiates filamentation.…”

Section: Introductionmentioning

confidence: 99%

“…The determination of (a/b) cr has been the focus of a number of studies, e.g., [11,10,9]. The physical mechanisms of symmetric merger have also been considered, e.g., [7,8,4,13,1,2]. In the more general interaction of two unequal size and/or strength (asymmetric) vortices, there is a greater range of flow behavior and the interaction may result in the destruction of the smaller/weaker vortex.…”

Section: Introductionmentioning

confidence: 99%

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Asymmetric vortex merger: mechanism and criterion

Brandt

Cichocki

Nomura

2009

Theor. Comput. Fluid Dyn.

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The merging of two unequal co-rotating vortices in a viscous fluid is investigated. Two-dimensional numerical simulations of initially equal sized Lamb-Oseen vortices with differing relative strengths are performed. Results show how the disparity in deformation rates between the vortices alters the interaction. Key physical mechanisms associated with vortex merging are identified. A merging criterion is formulated in terms of the relative timing of core detrainment and destruction. A critical strain parameter is defined to characterize the establishment of core detrainment. This parameter is shown to be directly related to the critical aspect ratio in the case of symmetric merger.

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The physics of vortex merger: Further insight

Cited by 38 publications

References 15 publications

A link between nonlinear self-organization and dissipation in drift-wave turbulence

A link between nonlinear self-organization and dissipation in drift-wave turbulence

Dynamics of two identical vortices in linear shear

Asymmetric vortex merger: mechanism and criterion

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