ORCID Profile
0000-0002-3912-4727
Current Organisation
Australian National University
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Research Topics
In Research Link Australia (RLA), "Research Topics" refer to ANZSRC FOR and SEO codes. These topics are either sourced from ANZSRC FOR and SEO codes listed in researchers' related grants or generated by a large language model (LLM) based on their publications.
Top 5 Research Topics
ANZSRC Field of Research (FoR)
Fluid Physics | Tropospheric and Stratospheric Physics | Complex Physical Systems | Geophysical Fluid Dynamics | Turbulent Flows | Power and Energy Systems Engineering (excl. Renewable Power) | Other Physical Sciences | Atmospheric Sciences | Biomechanical Engineering | Classical Physics | Environmental Technologies | Fluidisation and Fluid Mechanics | Environmental Engineering | Interdisciplinary Engineering | Physical Oceanography
ANZSRC Socio-Economic Objective (SEO)
Expanding Knowledge in the Physical Sciences | Atmospheric Processes and Dynamics | Expanding Knowledge in the Environmental Sciences | Land and Water Management of environments not elsewhere classified | Rehabilitation of Degraded Fresh, Ground and Surface Water Environments | Natural Hazards in Marine Environments | Expanding Knowledge in the Earth Sciences | Expanding Knowledge in the Biological Sciences | Wind Energy |
Related Links
Publications
Rolling spinners on the water surface
Publisher: American Association for the Advancement of Science (AAAS)
Date: 16-04-2021
Abstract: Fast-spinning discs on a liquid surface propagate along arbitrarily shaped boundaries, making a new type of surface vehicles.
Flight–crash events in turbulence
Publisher: Proceedings of the National Academy of Sciences
Date: 02-05-2014
Abstract: Irreversibility is a fundamental aspect of the evolution of natural systems, and quantifying its manifestations is a challenge in any attempt to describe nonequilibrium systems. In the case of fluid turbulence, an emblematic ex le of a system very far from equilibrium, we show that the motion of a single fluid particle provides a clear manifestation of time irreversibility. Namely, we observe that fluid particles tend to lose kinetic energy faster than they gain it. This is best seen by the presence of rare “flight–crash” events, where fast moving particles suddenly decelerate into a region where fluid motion is slow. Remarkably, the statistical signature of these events establishes a quantitative relation between the degree of irreversibility and turbulence intensity.
Extreme Capillary Wave Events Under Parametric Excitation
Publisher: Wiley
Date: 05-12-2015
Observation of internal kink instability purely driven by suprathermal electrons in the HL-1M tokamak
Publisher: IOP Publishing
Date: 05-2002
Multichannel visible spectroscopy diagnostic for particle transport studies in the H-1 heliac
Publisher: AIP Publishing
Date: 03-2003
DOI: 10.1063/1.1537033
Abstract: A multichannel spectroscopy diagnostic has been developed to study cross-field particle transport in the radiation-dominated low-temperature plasmas (Te& eV) in the H-1 heliac. The optical setup covers the full plasma minor radius in the poloidal plane collecting light from ten parallel chords arranged tangentially to the flux surfaces. The light collected from the plasma is coupled into optical fibers and through interference filters into photomultipliers. Two such ten-fiber arrays are aligned parallel to one another to allow the simultaneous monitoring of two different spectral lines. The net radial electron particle flux is determined from the continuity equation by integrating over the ionization source term in the steady-state partially ionized plasma. The diagnostic measures the neutral line intensities and their ratios (in case of helium using the line ratio technique) and also measures excited neutral and ion spectral lines (in case of the argon plasma transport studies). A comparative analysis of the radial particle transport in the low- and high-confinement regimes is presented.
Turbulence-Condensate Interaction in Two Dimensions
Publisher: American Physical Society (APS)
Date: 06-11-2008
Measurements of poloidal rotation velocity using cross-correlation spectroscopy in the H-1 heliac
Publisher: AIP Publishing
Date: 03-2003
DOI: 10.1063/1.1537032
Abstract: A correlation spectroscopy diagnostic [M.G. Shats and J. Howard, Fusion Eng. Des. 34–35, 271 (1997)] measures fluctuation spectra and local fluctuation intensities in a radiation-dominated plasma, such as the low-temperature plasma in the H-1 heliac (Te& eV, ne& ×1018 m−3). When the fluctuation coherence lengths in the poloidal and radial directions are shorter than the plasma radius, the cross-correlation function of the two crossed-sightline fluctuating intensities contains information about the fluctuations litude and their phase in the intersection volume. The optical setup on the H-1 heliac uses two nearly orthogonal views to image 20 optical fibers arranged into two linear arrays in the plasma poloidal cross section. A matrix of 10×10 cross-correlation functions is then analyzed to determine the poloidal phase velocity of the fluctuations, poloidal and radial correlation lengths, and the radial profiles of the fluctuations intensity. The results on the poloidal propagation velocity measured using the cross-correlation technique (time delay of the cross-correlation functions) are compared with the poloidal velocity measured using poloidally separated probes in the plasma. Both velocities are found to be in good agreement and also agree well with the E×B drift velocity in this plasma.
Extreme concentration fluctuations due to local reversibility of mixing in turbulent flows
Publisher: World Scientific Pub Co Pte Lt
Date: 10-05-2018
DOI: 10.1142/S0217984918400286
Abstract: Mixing of a passive scalar in a fluid (e.g. a radioactive spill in the ocean) is the irreversible process towards homogeneous distribution of a substance. In a moving fluid, due to the chaotic advection [H. Aref, J. Fluid Mech. 143 (1984) 1 J. M. Ottino, The Kinematics of Mixing: Stretching,Chaos and Transport (Cambridge University Press, Cambridge, 1989)] mixing is much faster than if driven by molecular diffusion only. Turbulence is known as the most efficient mixing flow [B. I. Shraiman and E. D. Siggia, Nature 405 (2000) 639]. We show that in contrast to spatially periodic flows, two-dimensional turbulence exhibits local reversibility in mixing, which leads to the generation of unpredictable strong fluctuations in the scalar concentration. These fluctuations can also be detected from the analysis of the fluid particle trajectories of the underlying flow.
Turbulence Decay Rate as a Measure of Flow Dimensionality
Publisher: American Physical Society (APS)
Date: 23-12-2010
Spectral energy transfer and generation of turbulent structures in toroidal plasma
Publisher: AIP Publishing
Date: 20-01-2004
DOI: 10.1063/1.1637607
Abstract: Nonlinear energy cascades in turbulent spectra are studied in the H-1 toroidal heliac [S. M. Hamberger et al., Fusion Technol. 17, 123 (1990)] using the spectral energy transfer estimation and the litude correlation technique. An inverse energy cascade of the spectral energy from the unstable range is shown to be responsible for the generation of the large-scale coherent structures dominating turbulence spectra. Among such structures are zonal flows which are also found to be generated via the inverse cascade. The generation of zonal flows is correlated with the increased strength in the nonlinear energy transfer. The onset of the strongly sheared radial electric field across the low–high (L–H) transition dramatically changes the energy transfer in the spectra and the spectral power of the fluctuations.
Confinement of surface spinners in liquid metamaterials
Publisher: Proceedings of the National Academy of Sciences
Date: 04-12-2019
Abstract: We show that rotating particles at the liquid–gas interface can be efficiently manipulated using the surface-wave analogue of optical lattices. Two orthogonal standing waves generate surface flows of counter-rotating half-wavelength unit cells, the liquid interface metamaterial, whose geometry is controlled by the wave phase shift. Here we demonstrate that by placing active magnetic spinners inside such metamaterials, one makes a powerful tool which allows manipulation and self-assembly of spinners, turning them into vehicles capable of transporting matter and information between autonomous metamaterial unit cells. We discuss forces acting on a spinner carried by a nonuniform flow and show how the forces confine spinners to orbit inside the same-sign vortex cells of the wave-driven flow. Reversing the spin, we move the spinner into an adjacent cell. By changing the spinning frequency or the wave litude, one can precisely control the spinner orbit. Multiple spinners within a unit cell self-organize into stable patterns, e.g., triangles or squares, orbiting around the center of the cell. Spinners having different frequencies can also be confined, such that the higher-frequency spinner occupies the inner orbit and the lower-frequency one circles on the outer orbit, while the orbital motions of both spinners are synchronized.
Propagating solitons generated by localized perturbations on the surface of deep water
Publisher: American Physical Society (APS)
Date: 16-02-2012
Experimental progress on zonal flow physics in toroidal plasmas
Publisher: IOP Publishing
Date: 19-09-2007
Turbulent transport reduction and randomization of coherent fluctuations by zonal flows in toroidal plasma
Publisher: American Physical Society (APS)
Date: 28-03-2003
Spectral condensation of turbulence in plasmas and fluids and its role in low-to-high phase transitions in toroidal plasma
Publisher: American Physical Society (APS)
Date: 28-04-2005
Mean E x B flows and GAM-like oscillations in the H-1 heliac
Publisher: IOP Publishing
Date: 06-03-2006
Inhibition of wave-driven two-dimensional turbulence by viscoelastic films of proteins
Publisher: American Physical Society (APS)
Date: 26-08-2015
Braid Entropy of Two-Dimensional Turbulence
Publisher: Springer Science and Business Media LLC
Date: 22-12-2015
DOI: 10.1038/SREP18564
Abstract: The evolving shape of material fluid lines in a flow underlies the quantitative prediction of the dissipation and material transport in many industrial and natural processes. However, collecting quantitative data on this dynamics remains an experimental challenge in particular in turbulent flows. Indeed the deformation of a fluid line, induced by its successive stretching and folding, can be difficult to determine because such description ultimately relies on often inaccessible multi-particle information. Here we report laboratory measurements in two-dimensional turbulence that offer an alternative topological viewpoint on this issue. This approach characterizes the dynamics of a braid of Lagrangian trajectories through a global measure of their entanglement. The topological length "Equation missing" of material fluid lines can be derived from these braids. This length is found to grow exponentially with time, giving access to the braid topological entropy "Equation missing" . The entropy increases as the square root of the turbulent kinetic energy and is directly related to the single-particle dispersion coefficient. At long times, the probability distribution of "Equation missing" is positively skewed and shows strong exponential tails. Our results suggest that "Equation missing" may serve as a measure of the irreversibility of turbulence based on minimal principles and sparse Lagrangian data.
Tunable diffusion in wave-driven two-dimensional turbulence
Publisher: Cambridge University Press (CUP)
Date: 27-02-2019
DOI: 10.1017/JFM.2019.82
Abstract: 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.
Spectrally condensed turbulence in thin layers
Publisher: AIP Publishing
Date: 12-2009
DOI: 10.1063/1.3275861
Abstract: We present experimental results on the properties of bounded turbulence in thin fluid layers. In contrast with the theory of two-dimensional (2D) turbulence, the effects of the bottom friction and of the spectral condensation of the turbulence energy are important in our experiment. Here we investigate how these two factors affect statistical moments of turbulent fluctuations. The inverse energy cascade in a bounded turbulent quasi-2D flow leads to the formation of a large coherent vortex (condensate) fed by turbulence. This vortex, depending on its strength, can substantially affect the turbulence statistics, even at small scales. Up to the intermediate strength of the condensate, the velocity moments similar to those in isotropic 2D turbulence are recovered by subtracting the coherent component from the velocity fields. A strong condensate leaves a footprint on the underlying turbulence it generates stronger non-Gaussianity and reduces the efficiency of the inverse energy cascade. Remarkably, the energy flux in the cascade derived from the third-order structure function using the Kolmogorov flux relation gives physically meaningful values in a broad range of experimental parameters regardless of the condensate strength. This result has important implications for the analysis of the atmospheric wind data in upper troposphere and lower stratosphere.
SIMULTANEOUS OBSERVATION OF ENERGY AND ENSTROPHY CASCADES IN THIN-LAYER TURBULENCE
Publisher: World Scientific Pub Co Pte Lt
Date: 2016
DOI: 10.1142/S201019451660185X
Abstract: We report the simultaneous observation of the inverse energy and direct enstrophy cascade in thin-layer turbulence. The experiments are conducted in an electromagnetically driven flow with layers of stratified fluid. Recent questions regarding the two-dimensionality of electromagnetically driven turbulence in such experiments are addressed.
Generation and reversal of surface flows by propagating waves
Publisher: Springer Science and Business Media LLC
Date: 10-08-2014
DOI: 10.1038/NPHYS3041
Observation of weak turbulence spectra of capillary waves
Publisher: Springer Berlin Heidelberg
Date: 2009
Suppression of Turbulence by Self-Generated and Imposed Mean Flows
Publisher: American Physical Society (APS)
Date: 16-10-2007
Universality of Kolmogorov law in spectrally condensed turbulence in thin layers
Publisher: Springer Berlin Heidelberg
Date: 2009
Inverse energy cascade correlated with turbulent-structure generation in toroidal plasma
Publisher: American Physical Society (APS)
Date: 06-10-2003
Capillary Rogue Waves
Publisher: American Physical Society (APS)
Date: 11-03-2010
Local anisotropy of laboratory two-dimensional turbulence affects pair dispersion
Publisher: AIP Publishing
Date: 02-2019
DOI: 10.1063/1.5082851
Abstract: 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- erging 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.
Generation of Vortex Lattices at the Liquid–Gas Interface Using Rotating Surface Waves
Publisher: MDPI AG
Date: 16-04-2019
Abstract: 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.
WAVE-GENERATED FLOWS ON THE WATER SURFACE
Publisher: World Scientific Pub Co Pte Lt
Date: 2016
DOI: 10.1142/S2010194516601794
Abstract: Predicting trajectories of fluid parcels on the water surface perturbed by waves is a difficult mathematical and theoretical problem. It is even harder to model flows generated on the water surface due to complex three-dimensional wave fields, which commonly result from the modulation instability of planar waves. We have recently shown that quasi-standing, or Faraday, waves are capable of generating horizontal fluid motions on the water surface whose statistical properties are very close to those in two-dimensional turbulence. This occurs due to the generation of horizontal vortices. Here we show that progressing waves generated by a localized source are also capable of creating horizontal vortices. The interaction between such vortices can be controlled and used to create stationary surface flows of desired topology. These results offer new methods of surface flow generation, which allow engineering inward and outward surface jets, large-scale vortices and other complex flows. The new principles can be also be used to manipulate floaters on the water surface and to form well-controlled Lagrangian coherent structures on the surface. The resulting flows are localized in a narrow layer near the surface, whose thickness is less than one wavelength.
Phase Randomization of Three-Wave Interactions in Capillary Waves
Publisher: American Physical Society (APS)
Date: 07-08-2009
Turbulence
Publisher: Wiley
Date: 20-04-2017
DOI: 10.1002/9781118476406.EMOE074
Abstract: Turbulence is a ubiquitous state for many flows in nature and engineering. As the flow velocity is increased, the nonlinear energy transfer generates fluid motion in a broad range of scales forming continuous wave number spectra of the kinetic energy. In isotropic homogeneous incompressible turbulence, energy flux is related to the third‐order velocity structure function via the Kolmogorov 4/5 law. In three‐dimensional turbulence, the energy is transferred from large to smaller scales in the process of the energy cascade. In two‐dimensional turbulence, energy is transferred from smaller to larger scales, the inverse energy cascade. Turbulence greatly increases the rate of mixing in fluids and dispersion. Transport of matter in turbulent flows requires Lagrangian description, in which the observer follows the fluid particles wherever they move. Here, we review the approaches to turbulence description in two and three dimensions.
Two-dimensional turbulence in three-dimensional flows
Publisher: AIP Publishing
Date: 11-09-2017
DOI: 10.1063/1.5000863
Abstract: This paper presents a review of experiments performed in three-dimensional flows that show behaviour associated with two-dimensional turbulence. Experiments reveal the presence of the inverse energy cascade in two different systems, namely, flows in thick fluid layers driven electromagnetically and the Faraday wave driven flows. In thick fluid layers, large-scale coherent structures can shear off the vertical eddies and reinforce the planarity of the flow. Such structures are either self-generated or externally imposed. In the Faraday wave driven flows, a seemingly three-dimensional flow is shown to be actually two-dimensional when it is averaged over several Faraday wave periods. In this system, a coupling between the wave motion and 2D hydrodynamic turbulence is uncovered.
TURBULENCE DRIVEN BY FARADAY SURFACE WAVES
Publisher: World Scientific Pub Co Pte Lt
Date: 2014
DOI: 10.1142/S2010194514603792
Abstract: We report experimental results which show that the particle motion on the surface perturbed by Faraday waves is similar to the fluid motion in 2D turbulence. It supports the inverse energy cascade or the spectral energy transfer from smaller to larger scales. The vertical acceleration ranges from the Faraday instability threshold up to the droplet nucleation threshold where the ripples are a couple of millimeters high. Such a configuration rules out any 2D assumption on the fluid motion. The motion of floaters on the surface of the Faraday waves is essentially three dimensional but its horizontal component shows unexpected analogy with two-dimensional turbulence. The presence of the inverse cascade is detected by measuring frequency spectra of the Lagrangian velocity and confirmed by computing the third moment of the horizontal Eulerian velocity fluctuations. This is a robust phenomenon observed in deep water in a broad range of flow energies and wavelengths. The emergence of such a phenomenology in Faraday waves broadens the applicability of features common to 2D turbulent flows to the context of surface wave phenomena which is prevalent in many systems.
Inverse Energy Cascade and Emergence of Large Coherent Vortices in Turbulence Driven by Faraday Waves
Publisher: American Physical Society (APS)
Date: 06-05-2013
Lagrangian scale of particle dispersion in turbulence
Publisher: Springer Science and Business Media LLC
Date: 17-06-2013
DOI: 10.1038/NCOMMS3013
Abstract: Transport of mass, heat and momentum in turbulent flows by far exceeds that in stable laminar fluid motions. As turbulence is a state of a flow dominated by a hierarchy of scales, it is not clear which of these scales mostly affects particle dispersion. Also, it is not uncommon that turbulence coexists with coherent vortices. Here we report on Lagrangian statistics in laboratory two-dimensional turbulence. Our results provide direct experimental evidence that fluid particle dispersion is determined by a single measurable Lagrangian scale related to the forcing scale. These experiments offer a new way of predicting dispersion in turbulent flows in which one of the low energy scales possesses temporal coherency. The results are applicable to oceanographic and atmospheric data, such as those obtained from trajectories of free-drifting instruments in the ocean.
Wave-based liquid-interface metamaterials
Publisher: Springer Science and Business Media LLC
Date: 09-02-2017
DOI: 10.1038/NCOMMS14325
Abstract: The control of matter motion at liquid–gas interfaces opens an opportunity to create two-dimensional materials with remotely tunable properties. In analogy with optical lattices used in ultra-cold atom physics, such materials can be created by a wave field capable of dynamically guiding matter into periodic spatial structures. Here we show experimentally that such structures can be realized at the macroscopic scale on a liquid surface by using rotating waves. The wave angular momentum is transferred to floating micro-particles, guiding them along closed trajectories. These orbits form stable spatially periodic patterns, the unit cells of a two-dimensional wave-based material. Such dynamic patterns, a mirror image of the concept of metamaterials, are scalable and biocompatible. They can be used in assembly applications, conversion of wave energy into mean two-dimensional flows and for organising motion of active swimmers.
Strong ExB Shear Flows in the Transport-Barrier Region inH
Publisher: American Physical Society (APS)
Date: 20-12-2006
Wave-particle interaction in the Faraday waves
Publisher: Springer Science and Business Media LLC
Date: 10-2015
DOI: 10.1140/EPJE/I2015-15106-4
Abstract: Wave motion in disordered Faraday waves is analysed in terms of oscillons or quasi-particles. The motion of these oscillons is measured using particle tracking tools and it is compared with the motion of fluid particles on the water surface. Both the real floating particles and the oscillons, representing the collective fluid motion, show Brownian-type dispersion exhibiting ballistic and diffusive mean squared displacement at short and long times, respectively. While the floating particles motion has been previously explained in the context of two-dimensional turbulence driven by Faraday waves, no theoretical description exists for the random walk type motion of oscillons. It is found that the r.m.s velocity ⟨μ̃(osc)⟩(rms) of oscillons is directly related to the turbulent r.m.s. velocity ⟨μ̃⟩(rms) of the fluid particles in a broad range of vertical accelerations. The measured ⟨μ̃(osc)⟩(rms) accurately explains the broadening of the frequency spectra of the surface elevation observed in disordered Faraday waves. These results suggest that 2D turbulence is the driving force behind both the randomization of the oscillons motion and the resulting broadening of the wave frequency spectra. The coupling between wave motion and hydrodynamic turbulence demonstrated here offers new perspectives for predicting complex fluid transport from the knowledge of wave field spectra and vice versa.
Three-Dimensional Fluid Motion in Faraday Waves: Creation of Vorticity and Generation of Two-Dimensional Turbulence
Publisher: American Physical Society (APS)
Date: 02-05-2014
Oscillon Dynamics and Rogue Wave Generation in Faraday Surface Ripples
Publisher: American Physical Society (APS)
Date: 14-09-2012
Xiaet al.Reply:
Publisher: American Physical Society (APS)
Date: 09-04-2009
Robust inverse energy cascade and turbulence structure in three-dimensional layers of fluid
Publisher: AIP Publishing
Date: 09-2011
DOI: 10.1063/1.3638620
Abstract: Here, we report the first evidence of the inverse energy cascade in a flow dominated by 3D motions. Experiments are performed in thick fluid layers where turbulence is driven electromagnetically. It is shown that if the free surface of the layer is not perturbed, the top part of the layer behaves as quasi-2D and supports the inverse energy cascade regardless of the layer thickness. Well below the surface the cascade survives even in the presence of strong 3D eddies developing when the layer depth exceeds half the forcing scale. In a bounded flow at low bottom dissipation, the inverse energy cascade leads to the generation of a spectral condensate below the free surface. Such coherent flow can destroy 3D eddies in the bulk of the layer and enforce the flow planarity over the entire layer thickness.
Modulation instability and capillary wave turbulence
Publisher: IOP Publishing
Date: 07-2010
Nonequilibrium Thermodynamics of Turbulence-Driven Rotors
Publisher: American Physical Society (APS)
Date: 24-06-2020
Diffusion of ellipsoids in laboratory two-dimensional turbulent flow
Publisher: AIP Publishing
Date: 08-2019
DOI: 10.1063/1.5113734
Abstract: 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 Lf. Large ellipsoids (aa & Lf) 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/Lf 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.
LAGRANGIAN CORRELATION AND SPECTRA IN 2D TURBULENCE
Publisher: World Scientific Pub Co Pte Lt
Date: 2014
DOI: 10.1142/S2010194514603780
Abstract: Transition from chaotic flow to turbulent flow is investigated in both the Eulerian and Lagrangian frame of reference. Eulerian spectra of the kinetic energy of the flow show the development of a hierarchy of scales, generation of a broad k -5/3 spectral range in developed turbulence. In the Lagrangian frame, single particle displacement is dominant by multiple scales for the chaotic flow. In fully developed turbulence, one single scale determines the transport properties, which is related to the most persistent scale in the system, the forcing scale.
Turbulence
Publisher: Wiley
Date: 20-04-2017
DOI: 10.1002/9781118476406.EMOE074
Abstract: Turbulence is a ubiquitous state for many flows in nature and engineering. As the flow velocity is increased, the nonlinear energy transfer generates fluid motion in a broad range of scales forming continuous wave number spectra of the kinetic energy. In isotropic homogeneous incompressible turbulence, energy flux is related to the third‐order velocity structure function via the Kolmogorov 4/5 law. In three‐dimensional turbulence, the energy is transferred from large to smaller scales in the process of the energy cascade. In two‐dimensional turbulence, energy is transferred from smaller to larger scales, the inverse energy cascade. Turbulence greatly increases the rate of mixing in fluids and dispersion. Transport of matter in turbulent flows requires Lagrangian description, in which the observer follows the fluid particles wherever they move. Here, we review the approaches to turbulence description in two and three dimensions.
Surface waves control bacterial attachment and formation of biofilms in thin layers
Publisher: American Association for the Advancement of Science (AAAS)
Date: 29-05-2020
Abstract: Wave-controlled transport in fluid provides a novel method to shape and promote biofilm formation for bioengineering applications.
Taylor Particle Dispersion during Transition to Fully Developed Two-Dimensional Turbulence
Publisher: American Physical Society (APS)
Date: 12-03-2014
Field theory spin and momentum in water waves
Publisher: American Association for the Advancement of Science (AAAS)
Date: 21-01-2022
Abstract: Spin is a fundamental yet nontrivial intrinsic angular momentum property of quantum particles or fields, which appears within relativistic field theory. The spin density in wave fields is described by the theoretical Belinfante-Rosenfeld construction based on the difference between the canonical and kinetic momentum densities. These quantities are usually considered as abstract and non-observable per se. Here, we demonstrate, both theoretically and experimentally, that the Belinfante-Rosenfeld construction naturally arises in gravity (water surface) waves. There, the canonical momentum is associated with the generalized Stokes drift phenomenon, while the spin is generated by subwavelength circular motion of water particles. Thus, we directly observe these fundamental field theory properties as microscopic mechanical properties of a classical wave system. Our findings shed light onto the nature of spin and momentum in wave fields, demonstrate the universality of relativistic field theory concepts, and offer a new platform for their studies.
Zonal flows, GAM, and radial electric field in the H-1 heliac
Publisher: Springer Science and Business Media LLC
Date: 12-2006
Rectification of chaotic fluid motion in two-dimensional turbulence
Publisher: American Physical Society (APS)
Date: 04-12-2018
Upscale energy transfer in thick turbulent fluid layers
Publisher: Springer Science and Business Media LLC
Date: 06-02-2011
DOI: 10.1038/NPHYS1910
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