Local anisotropy of laboratory two-dimensional turbulence affects pair dispersion

Xia, Hua; Nicolas, François; Faber, B. J.; Punzmann, Horst; Shats, Michael

doi:10.1063/1.5082851

Cited by 10 publications

(14 citation statements)

References 55 publications

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“…[13][14][15][16][17] This swarming motion of bacteria seems to share some similarities with the behavior of coherent bundles of fluid particles recently reported in laboratory turbulent 2D flows. 22,23 This similarity creates a tantalizing bridge between these two very distinct systems and highlights how the transport properties of chaotic flows are deeply connected to their Lagrangian structures.…”

Section: Discussionmentioning

confidence: 88%

“…scitation.org/journal/phf at moderate Reynolds numbers has an underlying Lagrangian fabric, which is composed of continuously evolving bundles of fluid particles. 22,23 These bundles have a characteristic width that is proportional to the turbulence forcing scale L f . Fluid particles moving together within such bundles execute collective random walks.…”

Section: Articlementioning

confidence: 99%

“…[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%

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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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Section: Discussionmentioning

confidence: 88%

Section: Articlementioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Diffusion of ellipsoids in laboratory two-dimensional turbulent flow

et al. 2019

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“…In wave-driven two-dimensional turbulence, a floating object can exploit the fluid erratic motion to fuel either directional propulsion or rotation [18]. It was shown that wave-driven turbulence possesses an underlying fabric which consists of riverlike structures [18][19][20]. The motion of a floating object can be strongly coupled with this flow fabric, if its shape is asymmetric.…”

Section: Introductionmentioning

confidence: 99%

Passive propulsion in turbulent flows

et al. 2019

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The ability of a device to exploit the energy of a flow to generate thrust is the main feature of passive propulsion. In a turbulent flow, such energy conversion is challenging due to the unpredictable and disordered fluid motion. In wave-driven turbulence, it has recently been demonstrated that asymmetric floating rotors can tap the energy of ambient fluctuations to fuel directed rotation. Here we report on the dynamics of asymmetric floating vehicles capable of passively propelling themselves in two-dimensional turbulence. We show experimentally how the shape of a floater and its rotational dynamics conspire to allow harvesting energy of the turbulent fluid motion. The translation and rotation of the floater are shown to be strongly coupled. The propulsion velocity and the rotational diffusion timescale depend on the relative size of the floating vehicle with respect to the turbulence forcing scale. The geometry of the floater is investigated in the range of circular-sector-shaped objects and a shape optimizing its propulsion is identified. At times larger than the rotational diffusion timescale, our results shed light on a substantial increase of the turbulent diffusion coefficient of anisotropic objects due to the coupling between propulsion and rotational diffusion.

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“…Waves generated using various plungers produce complex stationary surface flows which can be used to either confine surface particles, or to fetch them [8]. Another important class of surface flows investigated extensively since 2011 is the wave-driven two-dimensional turbulence (2D) [9][10][11][12][13][14]. Such turbulence is generated at the surface of liquids perturbed by strongly nonlinear Faraday waves.…”

Section: Introductionmentioning

confidence: 99%

Generation of Vortex Lattices at the Liquid–Gas Interface Using Rotating Surface Waves

Xia

Nicolas

Gorce

et al. 2019

Fluids

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In this paper, we demonstrate experimentally that by generating two orthogonal standing waves at the liquid surface, one can control the motion of floating microparticles. The mechanism of the vortex generation is somewhat similar to a classical Stokes drift in linear progression waves. By adjusting the relative phase between the waves, it is possible to generate a vortex lattice, seen as a stationary horizontal flow consisting of counter-rotating vortices. Two orthogonal waves which are phase-shifted by π / 2 create locally rotating waves. Such waves induce nested circular drift orbits of the surface fluid particles. Such a configuration allows for the trapping of particles within a cell of the size about half the wavelength of the standing waves. By changing the relative phase, it is possible to either create or to destroy the vortex crystal. This method creates an opportunity to confine surface particles within cells, or to greatly increase mixing of the surface matter over the wave field surface.

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Local anisotropy of laboratory two-dimensional turbulence affects pair dispersion

Cited by 10 publications

References 55 publications

Diffusion of ellipsoids in laboratory two-dimensional turbulent flow

Diffusion of ellipsoids in laboratory two-dimensional turbulent flow

Passive propulsion in turbulent flows

Generation of Vortex Lattices at the Liquid–Gas Interface Using Rotating Surface Waves

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