Rectification of chaotic fluid motion in two-dimensional turbulence

Nicolas, François; Xia, Hua; Punzmann, Horst; Shats, Michael

doi:10.1103/physrevfluids.3.124602

Cited by 16 publications

(34 citation statements)

References 34 publications

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“…This local anisotropy dominates both the pair separation and the exit time statistics bringing important deviations from statistical properties predicted in isotropic turbulence. We have recently shown that these bundles influence strongly turbulent mixing, 54 the transport of inertial particles, 55 or can even be utilized to design turbulence driven rotors 22 and self-propelled objects. 56…”

Section: Discussionmentioning

confidence: 99%

“…scitation.org/journal/phf the wave-driven turbulence, the underlying Lagrangian structure of the flow is dominated by locally anisotropic bundles of fluid trajectories. 22 Such anisotropic bundles should be responsible for modifications to the self-similar dispersion expected in isotropic turbulence and may bring important deviations from the classical Richardson-Obukhov law.…”

Section: Articlementioning

confidence: 99%

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Local anisotropy of laboratory two-dimensional turbulence affects pair dispersion

et al. 2019

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Experimental investigation of particle pair separation is conducted in two types of laboratory two-dimensional turbulence under a broad range of experimental conditions. In the range of scales corresponding to the inverse energy cascade inertial interval, the particle pair separation exhibits diffusive behaviour. The analysis of the pair velocity correlations suggests the existence of coherent bundles or clusters of non-diverging fluid particles. Such bundles are also detected using a recently developed topological tool based on the concept of braids. The bundles are observed as meandering streams whose width is determined by the turbulence forcing scale. In such locally anisotropic turbulence, the particle pair dispersion depends on the initial particle separation and on the width of the bundles.

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Section: Discussionmentioning

confidence: 99%

Section: Articlementioning

confidence: 99%

Local anisotropy of laboratory two-dimensional turbulence affects pair dispersion

et al. 2019

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“…It is interesting to note that the coupling between the flow fabric with large floating objects can give rise to interesting phenomena if the object has an asymmetric shape (Francois et al 2018). Recently, it has been demonstrated that such objects are able to extract energy from 2D turbulence and this offers methods to create turbulence-driven turbines or self-propelled vehicles (Francois et al 2018; Yang et al 2019).…”

Section: Discussionmentioning

confidence: 99%

Tunable diffusion in wave-driven two-dimensional turbulence

et al. 2019

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We report an abrupt change in the diffusive transport of inertial objects in wave-driven turbulence as a function of the object size. In these non-equilibrium two-dimensional flows, the turbulent diffusion coefficient $D$ of finite-size objects undergoes a sharp change for values of the object size $r_{p}$ close to the flow forcing scale $L_{f}$. For objects larger than the forcing scale ($r_{p}>L_{f}$), the diffusion coefficient is proportional to the flow energy $U^{2}$ and inversely proportional to the size $r_{p}$. This behaviour, $D\sim U^{2}/r_{p}$ , observed in a chaotic macroscopic system is reminiscent of a fluctuation–dissipation relation. In contrast, the diffusion coefficient of smaller objects ($r_{p}<L_{f}$) follows $D\sim U/r_{p}^{0.35}$. This result does not allow simple analogies to be drawn but instead it reflects strong coupling of the small objects with the fabric and memory of the out-of-equilibrium flow. In these turbulent flows, the flow structure is dominated by transient but long-living bundles of fluid particle trajectories executing random walk. The characteristic widths of the bundles are close to $L_{f}$. We propose a simple phenomenology in which large objects interact with many bundles. This interaction with many degrees of freedom is the source of the fluctuation–dissipation-like relation. In contrast, smaller objects are advected within coherent bundles, resulting in diffusion properties closely related to those of fluid tracers.

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“…[19][20][21] Moreover, correlation in time and in space originating from the swarming motion of bacteria may be qualitatively similar to the behavior of coherent bundles of fluid particles recently reported in the structure of laboratory turbulent 2D flows. 22,23 In laboratory 2D turbulence, it has been shown that the single particle dispersion of fluid tracers is determined by the turbulence kinetic energy and by a single Lagrangian length scale (which is close to the turbulence forcing scale L f ). [24][25][26][27][28] Studies of the dispersion of pairs of fluid tracers in such flows revealed that 2D turbulence…”

Section: Introductionmentioning

confidence: 99%

Diffusion of ellipsoids in laboratory two-dimensional turbulent flow

et al. 2019

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We report on the transport properties and orientational dynamics of ellipsoidal objects advected by laboratory two-dimensional turbulence. It is found that ellipsoids of different sizes have preferential direction of transport, either along their major axes or minor axes. The two components of the ellipsoid diffusion coefficient depend on the ratio of the length of the ellipsoids along major axes aa to the turbulence forcing scale L f. Large ellipsoids (aa > L f) diffuse faster in the direction parallel to their major axes. In contrast, small ellipsoids diffuse faster in the direction transverse to their major axes. We study this transition vs the ratio aa/L f and relate it to the coupling between translational and rotational motion of anisotropic objects. The features of the turbulent transport of ellipsoids can be understood by considering the interaction of these anisotropic objects with the underlying structure of two dimensional turbulent flows made of meandering coherent bundles.

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Rectification of chaotic fluid motion in two-dimensional turbulence

Cited by 16 publications

References 34 publications

Local anisotropy of laboratory two-dimensional turbulence affects pair dispersion

Local anisotropy of laboratory two-dimensional turbulence affects pair dispersion

Tunable diffusion in wave-driven two-dimensional turbulence

Diffusion of ellipsoids in laboratory two-dimensional turbulent flow

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