Accumulation of Heavy Particles in Bounded Vortex Flow

IJzermans, R.H.A.; Hagmeijer, Rob

doi:10.1007/1-4020-4977-3_9

Cited by 2 publications

(3 citation statements)

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“…1995). At even higher Stk, particles have sufficient inertia to be expelled from the vortex (Ijzermans & Hagmeijer 2006). Particles with small Stokes numbers, on the other hand, are concentrated in the strain‐dominated regions of the flow (Bec et al.…”

Section: Planktonic Interactions With the Cartoon Vortexmentioning

confidence: 99%

“…6) that particles with Stk above a critical value will tend to find a stable radius at which to orbit the axis, although vortex orientation with respect to the gravitational vector matters when the particles are not neutrally buoyant (Marcu et al 1995). At even higher Stk, particles have sufficient inertia to be expelled from the vortex (Ijzermans & Hagmeijer 2006). Particles with small Stokes numbers, on the other hand, are concentrated in the strain-dominated regions of the flow (Bec et al 2006;.…”

Section: Turbulence-plankton Interactions: a New Cartoonmentioning

confidence: 99%

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Turbulence‐plankton interactions: a new cartoon

et al. 2009

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IntroductionMarine life concentrates in two turbulent boundary layers, one just under the sea surface and one just over the sea bed. How turbulence affects marine life is a key, basic research question that also has high relevance in predicting effects of climate change. Global warming can be expected to increase mean upper-ocean stratification via temperature gradients and thereby suppress globalocean, mean turbulence intensity. At the same time, however, it will increase turbulence intensity locally and intermittently through more energetic storm events. That AbstractClimate change redistributes turbulence in both space and time, adding urgency to understanding of turbulence effects. Many analytic and analog models used to simulate and assess effects of turbulence on plankton rely on simple Couette flow. There shear rates are constant and spatially uniform, and hence so is vorticity. Over the last decade, however, turbulence research within fluid dynamics has focused on the structure of dissipative vortices in space and time. Vorticity gradients, finite net diffusion of vorticity and small radii of curvature of streamlines are ubiquitous features of turbulent vortices at dissipation scales but are explicitly excluded from simple, steady Couette flows. All of these flow components contribute instabilities that cause rotation of particles and so are important to simulate in future laboratory devices designed to assess effects of turbulence on nutrient uptake, particle coagulation, motility and predator-prey encounter in the plankton. The Burgers vortex retains these signature features of turbulence and provides a simplified ''cartoon'' of vortex structure and dynamics that nevertheless obeys the Navier-Stokes equations. Moreover, this idealization closely resembles many dissipative vortices observed in both the laboratory and the field as well as in direct numerical simulations of turbulence. It is simple enough to allow both simulation in numerical models and fabrication of analog devices that selectively reproduce its features. Exercise of such numerical and analog models promises additional insights into mechanisms of turbulence effects on passive trajectories and local accumulations of both living and nonliving particles, into solute exchange with living and nonliving particles and into more subtle influences on sensory processes and swimming trajectories of plankton, including demersal organisms and settling larvae in turbulent bottom boundary layers. The literature on biological consequences of vortical turbulence has focused primarily on the smallest, Kolmogorov-scale vortices of length scale g. Theoretical dissipation spectra and direct numerical simulation, however, indicate that typical dissipative vortices with radii of 7g to 8g, peak azimuthal speeds of order 1 cm s )1 and lifetimes of order 10 s or longer (and much longer for moderate pelagic turbulence intensities) deserve new attention in studies of biological effects of turbulence.

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Section: Planktonic Interactions With the Cartoon Vortexmentioning

confidence: 99%

Section: Turbulence-plankton Interactions: a New Cartoonmentioning

confidence: 99%

Turbulence‐plankton interactions: a new cartoon

et al. 2009

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“…To estimate the response of the particles to the flow, we defined the Stokes number following IJzermans and Hagmeijer (2006),

S t = \frac{t_{0} Γ}{a^{2}},

which represents the ratio of the characteristic time of the particles (defined in Equation 2) to a characteristic time of the vortex. For the PS particles St = [0.12,0.54], while for the PMMA particles St = [0.14,0.21].…”

Section: Sediment Transportmentioning

confidence: 99%

Sediment Transport and Morphodynamics Induced by a Translating Monopolar Vortex

2020

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We performed laboratory experiments to describe and quantify the transport of sediment and the changes in the bed due to a generic translating monopolar vortex. Experiments were performed inside a water-filled, square tank with a particle bed on the bottom and a vertical plate attached perpendicular to one of the sidewalls. The tank was placed on top of a rotating table to create the vortex by changing its rotation rate. This change created a current inside the tank that separated at the edge of the vertical plate, with the shear layer rolling up into a vortex. Once the vortex was formed, the table was promptly stopped. Sediment particles are brought into suspension and captured by the vortex, forming a conical region that moves with the vortex until the sediment resettles in the bed, changing the original bed morphology. Three different measurement techniques were used to obtain information about the flow velocities, the sediment in suspension, and the net changes in the bed. Changes in the bed morphology occur along the trajectory of the vortex, where a region of erosion is followed by a region of deposition. The strength of a vortex is the main parameter governing the capture and suspension of particles with similar characteristics. A power law relationship is found between the vortex strength and the net displaced particle volume. Experiments were also performed without sediment to determine if the presence of sediment could affect the vortex dynamics. However, a definitive answer requires more experiments to obtain reliable statistics.

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Accumulation of Heavy Particles in Bounded Vortex Flow

Cited by 2 publications

References 11 publications

Turbulence‐plankton interactions: a new cartoon

Turbulence‐plankton interactions: a new cartoon

Sediment Transport and Morphodynamics Induced by a Translating Monopolar Vortex

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