Quantitative Imaging of Concentrated Suspensions Under Flow

Isa, Lucio; Besseling, R.; Schofield, Andrew B.; Poon, Wilson

doi:10.1007/12_2009_38

Cited by 12 publications

(4 citation statements)

References 187 publications

(294 reference statements)

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“…in the concentrated regime, suspension develops distinct compressive particle normal stress (Deboeuf et al, 2009;Dbouk et al, 2013b), and the apparent viscosity of the mixture increases significantly with the solid volume fraction (Krieger and Dougherty, 1959). No relative slip between the fluid and solid phases for low Reynolds number flows has been measured in this regime to the accuracy of the experimental methods (Lyon and Leal , 1998a;Isa et al, 2010). For yet larger solid volume fraction, approaching the jamming/flowing transition φ → φ m , the apparent viscosity diverges, and a finite frictional yield stress is approached in this limit even when the base fluid is strictly Newtonian.…”

Section: Introductionmentioning

confidence: 96%

Confined flow of suspensions modelled by a frictional rheology

Lecampion

Garagash

2014

J. Fluid Mech.

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We investigate in detail the problem of confined pressure-driven laminar flow of neutrally buoyant non-Brownian suspensions using a frictional rheology based on the recent proposal of Boyer et al. (2011a). The friction coefficient (shear stress over particle normal stress) and solid volume fraction are taken as functions of the dimensionless viscous number I defined as the ratio between the fluid shear stress and the particle normal stress. We clarify the contributions of the contact and hydrodynamic interactions on the evolution of the friction coefficient between the dilute and dense regimes reducing the phenomenological constitutive description to three physical parameters. We also propose an extension of this constitutive framework from the flowing regime (bounded by the maximum flowing solid volume fraction) to the fully jammed state (the random close packing limit).We obtain an analytical solution of the fully-developed flow in channel and pipe for the frictional suspension rheology. The result can be transposed to dry granular flow upon appropriate redefinition of the dimensionless number I. The predictions are in excellent agreement with available experimental results for neutrally buoyant suspensions, when using the values of the constitutive parameters obtained independently from stress-controlled rheological measurements. In particular, the frictional rheology correctly predicts the transition from Poiseuille to plug flow and the associated particles migration with the increase of the entrance solid volume fraction.We also numerically solve for the axial development of the flow from the inlet of the channel/pipe toward the fully-developed state. The available experimental data are in good agreement with our numerical predictions, when using an accepted phenomenological description of the relative phase slip obtained independently from batch-settlement experiments. The solution of the axial development of the flow notably provides a quantitative estimation of the entrance length effect in pipe for suspensions when the continuum assumption is valid. Practically, the latter requires that the predicted width of the central (jammed) plug is wider than one particle diameter. A simple analytical expression for development length, inversely proportional to the gap-averaged diffusivity of a frictional suspension, is shown to encapsulate the numerical solution in the entire range of flow conditions from dilute to dense.

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Section: Introductionmentioning

confidence: 96%

Confined flow of suspensions modelled by a frictional rheology

Lecampion

Garagash

2014

J. Fluid Mech.

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“…7,8 The simultaneous application of controlled stresses and the visualization of evolving morphologies in bulk materials typically requires confocal microscopes coupled to customized shear cells. 9 The necessity to scan large volumes across the geometry gap limits the range of accessible shear rates or restricts the observation to slices of material in proximity of solid boundaries. 7,10 These limitations can be circumvented by moving from bulk to truly two-dimensional (2D) systems.…”

Section: Introductionmentioning

confidence: 99%

Colloidal binary mixtures at fluid–fluid interfaces under steady shear: structural, dynamical and mechanical response

et al. 2015

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We experimentally study the link between structure, dynamics and mechanical response of two-dimensional (2D) binary mixtures of colloidal microparticles spread at water/oil interfaces. The particles are driven into steady shear by a microdisk forced to rotate at a controlled angular velocity. The flow causes particles to layer into alternating concentric rings of small and big colloids. The formation of such layers is linked to the local, position-dependent shear rate, which triggers two distinct dynamical regimes: particles either move continuously (“Flowing”) close to the microdisk, or exhibit intermittent “Hopping” between local energy minima farther away. The shear-rate-dependent surface viscosity of the monolayers can be extracted from a local interfacial stress balance, giving “macroscopic” flow curves whose behavior corresponds to the distinct microscopic regimes of particle motion. Hopping Regions reveal a higher resistance to flow compared to the Flowing Regions, where spatial organization into layers reduces dissipation.

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“…Hence, there is a need for complementary experimental measurements that bridge these two limits by exploring relatively large volumes with single particle resolution, and that are capable of distinguishing between the various proposed models. Here, by combining fast confocal microscopy (21,22) with simultaneous rheological measurements (21,23), we systematically correlate the real-space microstructure of concentrated hard-sphere suspensions with their flow properties.…”

mentioning

confidence: 99%

Imaging the Microscopic Structure of Shear Thinning and Thickening Colloidal Suspensions

Cheng

McCoy

Israelachvili

et al. 2011

Science

462

382

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The viscosity of colloidal suspensions varies with shear rate, an important effect encountered in many natural and industrial processes. Although this non-Newtonian behavior is believed to arise from the arrangement of suspended particles and their mutual interactions, microscopic particle dynamics are difficult to measure. By combining fast confocal microscopy with simultaneous force measurements, we systematically investigate a suspension's structure as it transitions through regimes of different flow signatures. Our measurements of the microscopic single-particle dynamics show that shear thinning results from the decreased relative contribution of entropic forces and that shear thickening arises from particle clustering induced by hydrodynamic lubrication forces. This combination of techniques illustrates an approach that complements current methods for determining the microscopic origins of non-Newtonian flow behavior in complex fluids.

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Quantitative Imaging of Concentrated Suspensions Under Flow

Cited by 12 publications

References 187 publications

Confined flow of suspensions modelled by a frictional rheology

Confined flow of suspensions modelled by a frictional rheology

Colloidal binary mixtures at fluid–fluid interfaces under steady shear: structural, dynamical and mechanical response

Imaging the Microscopic Structure of Shear Thinning and Thickening Colloidal Suspensions

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