Dipoles and streams in two-dimensional turbulence

Jiménez, Javier

doi:10.1017/jfm.2020.769

Cited by 13 publications

(26 citation statements)

References 69 publications

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“…The results in [4] extended the previous models in some interesting directions, especially regarding the decay of unforced turbulence in the early period in which the spectral scale of the energy has not grown enough to be affected by the simulation domain. It was found that the largest structures of the kinetic energy take the form of elongated high-speed jets, flanked by a subset of large vortices that move relatively slowly with respect to the global root-mean square (r.m.s.)…”

Section: Introductionsupporting

confidence: 68%

“…Case N L init /L q 0 L/ν N t λ ω0 /L λ q0 /L ω 0 t F ω F /ω 0 q F /q 0 Symbol T512 The next-to-last two columns in this table were wrong in [4]. The present ones are believed to be correct.…”

Section: Numerical Experimentsmentioning

confidence: 76%

“…The data used in this paper are mostly those in [4], to where the reader is referred for details. Simulations of decaying nominally isotropic two-dimensional turbulence are performed in a doubly periodic square box of side L, using a standard spectral Fourier code dealiased by the 2/3 rule.…”

Section: Numerical Experimentsmentioning

confidence: 99%

“…This paper is part of a sequence that began as an investigation on whether an automatic computer search of 'relevant' features in decaying two-dimensional turbulence could be used to suggest new ideas about the organisation of the flow [1]. That paper was continued in [2,3], mostly from the point of view of how such a search should be organised, and of its possible relation to automatic learning, and eventually led in [4] into an analysis of the flow itself. It is with the conclusions of this last paper that the present one deals.…”

Section: Introductionmentioning

confidence: 99%

“…The cascade of energy towards large scales corresponds to the growth of these jets. It was speculated in [4] that the slowly moving vortex dipoles that flank the jets form a largescale collective structure that can approximately be described as a 'crystal', and it was further speculated that the formation of the dipoles responds to a tendency of the flow to organise into low-energy configurations. This will be shown below to be the case, even if it may be considered counter-intuitive in a system, like two-dimensional turbulence, which dissipates enstrophy rather than energy, and in which the latter could be expected to 'lag behind' the decay of the former.…”

Section: Introductionmentioning

confidence: 99%

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Collective organisation and screening in two-dimensional turbulence

Jiménez

2021

Preprint

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Following recent evidence that the vortices in decaying two-dimensional turbulence can be classified into small-mobile, and large-quasi-stationary, this paper examines the evidence that the latter might be considered a 'crystal' whose formation embodies the inverse cascade of energy towards larger scales. Several diagnostics of order are applied to the ostensibly disordered large vortices. It is shown that their geometric arrangement is substantially more regular than random, that they move more slowly than could be expected from simple meanfield arguments, and that their energy is significantly lower than in a random reorganisation of the same vortices. This is traced to screening of long-range interactions by the preferential association of vortices of opposite sign, and it is argued that this is due to the mutual capture of corrotating vortices, in a mechanism closer to tidal disruption than to electrostatic screening. Finally, the possible relation of these 'stochastic crystals' to fixed points of the dynamical system representation of the turbulence flow is briefly examined.

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Section: Introductionsupporting

confidence: 68%

Section: Numerical Experimentsmentioning

confidence: 76%

Section: Numerical Experimentsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Collective organisation and screening in two-dimensional turbulence

Jiménez

2021

Preprint

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Pathway dynamics to double-cell premixed flames in lean hydrogen–air mixtures

Domínguez-González,

Encinar,

Martínez-Ruiz

2024

Proceedings of the Combustion Institute

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Selective energy and enstrophy modification of two-dimensional decaying turbulence

2023

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In two-dimensional decaying homogeneous isotropic turbulence, kinetic energy and enstrophy are respectively transferred to larger and smaller scales. In such spatiotemporally complex dynamics, it is challenging to identify the important flow structures that govern this behaviour. We propose and employ numerically two flow-modification strategies that leverage the inviscid global conservation of energy and enstrophy to design external forcing inputs that change these quantities selectively and simultaneously, and drive the system towards steady-state or other late-stage behaviour. One strategy employs only local flow field information, while the other is global. We observe various flow structures excited by these inputs and compare them with recent literature. Energy modification is characterized by the excitation of smaller wavenumber structures in the flow than enstrophy modification.

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Dipoles and streams in two-dimensional turbulence

Abstract: Abstract

Cited by 13 publications

References 69 publications

Collective organisation and screening in two-dimensional turbulence

Collective organisation and screening in two-dimensional turbulence

Pathway dynamics to double-cell premixed flames in lean hydrogen–air mixtures

Selective energy and enstrophy modification of two-dimensional decaying turbulence

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