Time persistence of floating-particle clusters in free-surface turbulence

Lovecchio, Salvatore; Marchioli, Cristian; Soldati, Alfredo

doi:10.1103/physreve.88.033003

Cited by 39 publications

(41 citation statements)

References 23 publications

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“…[22], in which an increase of the compressibility factor C was associated with an important upscale energy transfer, we find that compressibility is larger for larger Rer , when the upscale energy transfer is proportionally stronger. We also remark that a compressibility factor larger than the critical value C = 0.5 is of significant importance: it suggests the occurrence of extreme events (velocity sources and sinks, 033010-5 associated to pointlike structures), which might have strong influence on the dispersion of chemical species and particles in free-surface flows [1] but also in other flow instances [23],…”

Section: B Flow Topology and Energy Cascadementioning

confidence: 89%

“…This flow structure is also proven responsible for the highly nonuniform distribution patterns of biological microorganisms [1,2], which have an additional role onto the chemical and biological species cycles in open water bodies. Understanding the paramount role of turbulence at a free surface may therefore have strong environmental implications at short and long time horizons (global warming, future climate changes).…”

Section: Introductionmentioning

confidence: 99%

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Upscale energy transfer and flow topology in free-surface turbulence

2015

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Free-surface turbulence, albeit constrained onto a two-dimensional space, exhibits features that barely resemble predictions of simplified two-dimensional modeling. We demonstrate that, in a three-dimensional open channel flow, surface turbulence is characterized by upscale energy transfer, which controls the long-term evolution of the larger scales. We are able to associate downscale and upscale energy transfer at the surface with the two-dimensional divergence of velocity. We finally demonstrate that surface compressibility confirms the strongly three-dimensional nature of surface turbulence.

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Section: B Flow Topology and Energy Cascadementioning

confidence: 89%

Section: Introductionmentioning

confidence: 99%

Upscale energy transfer and flow topology in free-surface turbulence

2015

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“…[55], at least in the body of the distribution. The algebraic tails P (z) ∼ z −2 that are due to caustic singularities are not reproduced by (93). This is due to the fact that the z 2 -term in Eq.…”

Section: Steady-state Distributionsmentioning

confidence: 97%

“…It is nevertheless interesting to consider compressible flows. Particles floating on a turbulent flow, for example, experience a compressible surface flow [89][90][91][92][93]. More generally particle dynamics in partly compressible flows has been studied [94][95][96], see Ref.…”

Section: Statistical Model For the Velocity Fieldmentioning

confidence: 99%

Statistical models for spatial patterns of heavy particles in turbulence

Gustavsson

Mehlig

2016

Advances in Physics

139

208

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The dynamics of heavy particles suspended in turbulent flows is of fundamental importance for a wide range of questions in astrophysics, atmospheric physics, oceanography, and technology. Laboratory experiments and numerical simulations have demonstrated that heavy particles respond in intricate ways to turbulent fluctuations of the carrying fluid: non-interacting particles may cluster together and form spatial patterns even though the fluid is incompressible, and the relative speeds of nearby particles can fluctuate strongly. Both phenomena depend sensitively on the parameters of the system. This parameter dependence is difficult to model from first principles since turbulence plays an essential role. Laboratory experiments are also very difficult, precisely since they must refer to a turbulent environment. But in recent years it has become clear that important aspects of the dynamics of heavy particles in turbulence can be understood in terms of statistical models where the turbulent fluctuations are approximated by Gaussian random functions with appropriate correlation functions. In this review we summarise how such statistical-model calculations have led to a detailed understanding of the factors that determine heavy-particle dynamics in turbulence. We concentrate on spatial clustering of heavy particles in turbulence. This is an important question because spatial clustering affects the collision rate between the particles and thus the long-term fate of the system.

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“…This phenomenon is counterintuitive, because the level of clustering would be expected to increase when the correlation of the flow is nonzero. Thus, the study by [6] raises the questions of the interplay between compressibility and temporal correlation in turbulent flows and of the degree of universality of the weak-strong clustering transition [for further studies on clustering in turbulent surface flows, see 7,14,24,25,28,32,35,39]. The investigation of the universality of this phenomenon is particulartly interesting in the light of previous findings of non-universal transport properties in random compressible flows for passive scalar fields [15].…”

Section: Introductionmentioning

confidence: 98%

Weak–strong clustering transition in renewing compressible flows

Dhanagare¹,

Musacchio²,

Vincenzi³

2014

J. Fluid Mech.

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We investigate the statistical properties of Lagrangian tracers transported by a time-correlated compressible renewing flow. We show that the preferential sampling of the phase space performed by tracers yields significant differences between the Lagrangian statistics and its Eulerian counterpart. In particular, the effective compressibility experienced by tracers has a non-trivial dependence on the time correlation of the flow. We examine the consequence of this phenomenon on the clustering of tracers, focusing on the transition from the weak-to the strong-clustering regime. We find that the critical compressibility at which the transition occurs is minimum when the time correlation of the flow is of the order of the typical eddy turnover time. Further, we demonstrate that the clustering properties in time-correlated compressible flows are non-universal and are strongly influenced by the spatio-temporal structure of the velocity field.

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Time persistence of floating-particle clusters in free-surface turbulence

Cited by 39 publications

References 23 publications

Upscale energy transfer and flow topology in free-surface turbulence

Upscale energy transfer and flow topology in free-surface turbulence

Statistical models for spatial patterns of heavy particles in turbulence

Weak–strong clustering transition in renewing compressible flows

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