Shear viscosity of settling suspensions

Ferrini, F.; Ercolani, D.; Cindio, Bruno de; Nicodemo, L.; Nicolais, L.; Ranaudo, S.

doi:10.1007/bf01542776

Cited by 87 publications

(46 citation statements)

References 12 publications

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“…If mixture viscosity effects are neglected by setting [µ] = 0.0, the transport rate increases by 44 %. A decrease of similar magnitude relative to the baseline can be realized by setting [µ] = 5.0, corresponding to very angular particles (Ferrini et al 1979), which underscores the importance of considering shape effects on bulk particle motion. The filter size does appear to have an influence on the results, but for h 2d p , the sensitivity to h is minimized.…”

Section: Discussionmentioning

confidence: 72%

“…The variation of the effective viscosity of the sediment-fluid suspension is modelled using a modified version of the Eilers (1941) equation (Ferrini et al 1979) as…”

Section: Fluid Motionmentioning

confidence: 99%

“…Aside from particle shape, factors such as microstructural changes with shear rate, and particle polydispersivity are known to influence µ eff in complex ways (Stickel & Powell 2005). Equation (2.26) does not explicitly account for these factors, but has been shown to closely reproduce the behaviour of a variety of particle-fluid mixtures at high shear rates (Ferrini et al 1979) relevant to the present conditions. The unresolved subgrid-scale turbulent stresses can be modelled using a large-eddy simulation approach, thereby adding a turbulent contribution to µ eff .…”

Section: Fluid Motionmentioning

confidence: 99%

“…For monodisperse spherical particles the intrinsic viscosity, [µ], in such a model is accepted to be 2.5 (Stickel & Powell 2005), and the behaviour of nonspherical particle suspensions is compatible with increased values of [µ] (Ferrini et al 1979). Following the recommendations of Penko, Calantoni & Slinn (2009), [µ] = 3.0 is chosen for natural sands in this paper.…”

Section: Numerical Implementationmentioning

confidence: 99%

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Particle based modelling and simulation of natural sand dynamics in the wave bottom boundary layer

Finn

Apte

2016

J. Fluid Mech.

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Sand transport and morphological change occur in the wave bottom boundary layer due to sand particle interactions with an oscillatory flow and granular interactions between particles. Although these interactions depend strongly on the characteristics of the particle population, i.e. size and shape, little is known about how natural sand particles behave under oscillatory conditions and how variations in particle size influence transport behaviour. To enable this to be studied numerically, an Euler-Lagrange point-particle model is developed which can capture the individual and collective dynamics of subaqueous natural sand grains. Special treatments for particle collision, friction and hydrodynamic interactions are included to take into account the wide size and shape variations in natural sands. The model is used to simulate sand particle dynamics in two asymmetric oscillatory flow conditions corresponding to the vortex ripple experiments of Van der Werf et al. (J. Geophys. Res., vol. 112, 2007, F02012) and the sheet-flow experiments of O'Donoghue & Wright (Coast. Engng, vol. 50, 2004, pp. 117-138). A comparison of the phase resolved velocity and concentration fields shows overall excellent agreement between simulation and experiments. The particle based datasets are used to investigate the spatio-temporal dynamics of the particle-size distribution and the influence of three-dimensional vortical features on particle entrainment and suspension processes. For the first time, it is demonstrated that even for the relatively well-sorted medium-size sands considered here, the characteristics of the local grain size population exhibit significant space-time variation. Both conditions demonstrate a distinct coarse-over-fine armouring at the bed surface during low-velocity phases, which restricts the vertical mobility of finer fractions in the bed, and also results in strong pickup events involving disproportionately coarse fractions. The near-bed layer composition is seen to be very dynamic in the sheet-flow condition, while it remains coarse through most of the cycle in the vortex ripple condition. Particles in suspension spend more time sampling the upward directed parts of these flows, especially the smaller fractions, which delays particle settling and enhances the vertical size sorting of grains in suspension. For the submillimetre grain sizes considered, most † Email address for correspondence: J.Finn@liv.ac.uk

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Section: Discussionmentioning

confidence: 72%

“…The variation of the effective viscosity of the sediment-fluid suspension is modelled using a modified version of the Eilers (1941) equation (Ferrini et al 1979) as…”

Section: Fluid Motionmentioning

confidence: 99%

Section: Fluid Motionmentioning

confidence: 99%

Section: Numerical Implementationmentioning

confidence: 99%

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Particle based modelling and simulation of natural sand dynamics in the wave bottom boundary layer

Finn

Apte

2016

J. Fluid Mech.

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“…; N13). Drag force ranges in fluidized substrate calculated using 1<R B /R E <3 and the following liquid/particle viscosity models: F&A (Frankel and Acrivos, 1967); K&D (Krieger and Dougherty, 1959); E+F (Eilers, 1941;Ferrini et al, 1979); and M&P (Maron and Pierce, 1956). The plot shows that although E. directus is not strong enough to move through a static substrate, drag forces experienced in fluidized substrates are within its strength capabilities.…”

Section: Burrowing Drag Reduction Due To Localized Fluidizationmentioning

confidence: 99%

Localized fluidization burrowing mechanics ofEnsis directus

Winter

Deits

Hosoi

2012

Journal of Experimental Biology

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SUMMARYMuscle measurements of Ensis directus, the Atlantic razor clam, indicate that the organism only has sufficient strength to burrow a few centimeters into the soil, yet razor clams burrow to over 70cm. In this paper, we show that the animal uses the motions of its valves to locally fluidize the surrounding soil and reduce burrowing drag. Substrate deformations were measured using particle image velocimetry (PIV) in a novel visualization system that enabled us to see through the soil and watch E. directus burrow in situ. PIV data, supported by soil and fluid mechanics theory, show that contraction of the valves of E. directus locally fluidizes the surrounding soil. Particle and fluid mixtures can be modeled as a Newtonian fluid with an effective viscosity based on the local void fraction. Using these models, we demonstrate that E. directus is strong enough to reach full burrow depth in fluidized soil, but not in static soil. Furthermore, we show that the method of localized fluidization reduces the amount of energy required to reach burrow depth by an order of magnitude compared with penetrating static soil, and leads to a burrowing energy that scales linearly with depth rather than with depth squared.

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Rheological and mechanical characterization of polypropylene-based wood plastic composites

2015

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The aim of this article is to investigate the influence of filler content and temperature on the rheological, mechanical, and thermal properties of wood flour polypropylene composites (WPCs). Testing WPCs at high temperatures and percentages of filler is extremely challenging because of reduced linear viscoelastic region, high viscosity, and degradation. In this work, a complete characterization of WPCs with different filler percentages (0–70 wt%) has been made. Rheological tests are performed at 170°C for the WPCs and in the 170–200°C range for neat polypropylene. A single master curve is obtained using two shift factors that can be described by a modified Eilers model and a Williams‐Landel‐Ferry equation. This master curve, fitted with a Carreau‐Yasuda model, can be very useful for predicting the viscosity of WPCs at temperatures that are typically used during processing and for any percentage of filler. POLYM. COMPOS., 37:3460–3473, 2016. © 2015 Society of Plastics Engineers

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Shear viscosity of settling suspensions

Cited by 87 publications

References 12 publications

Particle based modelling and simulation of natural sand dynamics in the wave bottom boundary layer

Particle based modelling and simulation of natural sand dynamics in the wave bottom boundary layer

Localized fluidization burrowing mechanics ofEnsis directus

Rheological and mechanical characterization of polypropylene-based wood plastic composites

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