Turbulent clustering of initially well-mixed buoyant particles on a free-surface by Lagrangian coherent structures

Pratt, Kenneth R.; True, Aaron C.; Crimaldi, John P.

doi:10.1063/1.4990774

Cited by 11 publications

(5 citation statements)

References 30 publications

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“…In multiparticle systems, free surface turbulence has a determining effect on the particles floating on the surface. Pratt et al [ 18 ] showed that Lagrangian coherent structures generated by a turbulent flow near the gas–liquid free surface cause clustering of the initially well-mixed buoyant particles floating on it. The results of another study [ 19 ] suggested the same phenomena.…”

Section: Introductionmentioning

confidence: 99%

Incorporation of Powder Particles into an Impeller-Stirred Liquid Bath through Vortex Formation

2021

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The present study addresses the incorporation of fine particles into liquids via the creation of a large-scale swirling vortex on the liquid free surface using a rotary impeller positioned along the axis of a cylindrical vessel. Four types of particles are used in the experiments to investigate the incorporation efficiency of the particles into a water bath under different impeller rotation speeds. Additionally, the vortex characteristics are investigated numerically. The results reveal that two factors, namely the particle wettability and turbulent oscillations at the bottom part of vortex surface, play dominant roles in determining the particle incorporation behavior. Hydrophobic particles are incapable of being incorporated into the water bath under any of the conditions examined in the present study. Partly wettable particles are entrained into the water bath, with the efficiency increasing with the impeller rotation speed and particle size. This is because an increase in the impeller rotation speed causes vortex deformation, whereby its bottom part approaches the impeller blades where the turbulent surface oscillations reach maximum amplitudes. Another possible mechanism of particle incorporation is the effect of capillary increases of liquid into the spaces between particles, which accumulate on the bottom surface of the vortex.

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Section: Introductionmentioning

confidence: 99%

Incorporation of Powder Particles into an Impeller-Stirred Liquid Bath through Vortex Formation

2021

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“…The outlet jet velocity is another factor that can be modified to change the strength of the turbulence. Pratt et al. (2017) observed that increasing the input voltage of the pumps (which controls jet velocity and subsequently changes the jet outlet Reynolds number) increased and the dissipation rate while remained nearly constant.…”

Section: Actuator-based Turbulence-generation Mechanismsmentioning

confidence: 98%

“…2015; Pujara et al. 2018; Tinklenberg, Guala & Coletti 2023), the dissolution of large particles (Oehmke & Variano 2021), clustering of particles (Pratt, True & Crimaldi 2017; Petersen, Baker & Coletti 2019) and the melting of ice in turbulence (McCutchan 2020). Table 4 lists the known facilities that use RJAs for zero-mean-flow turbulence generation with their concomitant turbulence characteristics.…”

Section: Actuator-based Turbulence-generation Mechanismsmentioning

confidence: 99%

“…Krawczynski et al 2006;Krawczynski, Renou & Danaila 2010), but they may not necessarily achieve zero-mean-flow HIT. Random jet arrays have been used widely to investigate a variety of topics, such as bed morphology and sediment transport (Johnson & Cowen 2020), the effect of background flow on jets (Lavertu 2006;Khorsandi, Gaskin & Mydlarski 2013), the process of homogeneous electrodeposition in turbulence (Delbos et al 2009), the kinematics of particles (Bellani et al 2012;Meyer, Byron & Variano 2013;Byron et al 2015;Pujara et al 2018;Tinklenberg, Guala & Coletti 2023), the dissolution of large particles (Oehmke & Variano 2021), clustering of particles (Pratt, True & Crimaldi 2017;Petersen, Baker & Coletti 2019) and the melting of ice in turbulence (McCutchan 2020). Table 4 lists the known facilities that use RJAs for zero-mean-flow turbulence generation with their concomitant turbulence characteristics.…”

Section: Turbulence Generation Via Jet Arraysmentioning

confidence: 99%

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Laboratory generation of zero-mean-flow homogeneous isotropic turbulence: non-grid approaches

Ghazi Nezami,

Byron,

Johnson

2023

Flow

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Over the years, many facilities have been developed to study turbulent flow in the laboratory. Homogeneous isotropic turbulence (HIT) with zero mean flow provides a unique environment for investigating fundamental aspects and specific applications of turbulent flow. We provide an extensive overview of laboratory facilities that generate incompressible zero-mean-flow HIT using different types of actuators and configurations. Reviewed facilities cover a variety of geometries and sizes, as well as forcing style (e.g. symmetric versus asymmetric and unsteady versus steady). We divide facilities into four categories, highlighting links between their geometries and the statistics of the flows they generate. We then compare published data to uncover similarities and differences among various turbulence-generation mechanisms. We also compare the decay of turbulence in zero-mean-flow facilities with that observed in wind and water tunnels, and we analyse the connections between flow characteristics and physical aspects of the facilities. Our results emphasize the importance of considering facility geometry and size together with the strength and type of actuators when studying zero-mean-flow HIT. Overall, we provide insight into how to optimally design and build laboratory facilities that generate zero-mean-flow HIT.

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“…LC is often identified by the accumulation of positively buoyant material into patches on the surface at the regions of downwelling between pairs of counter‐rotating vortices (Yang et al 2014; Chang et al 2019). Such turbulent clustering of buoyant particles on a free surface is formed during LC as the two‐dimensional (2D) surface flow becomes non‐divergence‐free (Pratt et al 2017). These windrows are streaks of variable length (2 m to 1 km) aligned with each Langmuir cell oriented in the direction of the wind.…”

Section: Figmentioning

confidence: 99%

An experimental Stommel Retention Zone facility with an application to oil droplet dispersion

Gurung

Smith

Zeidi

et al. 2022

Limnology & Ocean Methods

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Stommel Retention Zones (SRZs) associated with wind-driven Langmuir circulation (LC) facilitate the subsurface retention of particles and thus affect processes such as oil spill dispersion, sediment suspension, oil-particle aggregation, and plankton distribution. Since the effect of SRZs on these processes is difficult to study in the field, we present a novel laboratory facility designed to recreate the counterrotating vortex pair flow pattern associated with small-scale SRZs of various strengths in two dimensions (2D). We then inject an oil jet into this facility to study buoyant oil droplet retention in these SRZs. 2D particle image velocimetry and hybrid Reynolds-averaged Navier-Stokes/large eddy simulation are used to characterize the flow. Large-scale oil droplet trajectories in the SRZs are visualized, and oil droplet statistics in the downwelling region and vortex core are measured using high-magnification brightfield imaging and a droplet detection algorithm. Values of maximum velocity (7.7-32.2 mm s À1 ), turbulent kinetic energy (10 À6 to 10 À4 m 2 s À2 ), and turbulent kinetic energy dissipation rate (10 À7 to 10 À5 m 2 s À3 ) in the downwelling region of the facility fall within the range of values observed in the field. Flow field strength strongly influences oil droplet trajectories, the shape and size of the SRZ, and oil droplet statistics over time, with stronger flows retaining larger oil droplets in the downwelling region over longer periods of time. Indeed, droplets of almost 400 μm diameter are observed in the downwelling region after almost 10 min for the strongest flow. The facility may be used to study the behavior of microplastics, sediments, and zooplankton in LC in the future.

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Turbulent clustering of initially well-mixed buoyant particles on a free-surface by Lagrangian coherent structures

Cited by 11 publications

References 30 publications

Incorporation of Powder Particles into an Impeller-Stirred Liquid Bath through Vortex Formation

Incorporation of Powder Particles into an Impeller-Stirred Liquid Bath through Vortex Formation

Laboratory generation of zero-mean-flow homogeneous isotropic turbulence: non-grid approaches

An experimental Stommel Retention Zone facility with an application to oil droplet dispersion

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