Slip and Flow of Hard-Sphere Colloidal Glasses

Ballesta, Pierre; Besseling, R.; Isa, Lucio; Petekidis, George; Poon, Wilson

doi:10.1103/physrevlett.101.258301

Cited by 106 publications

(115 citation statements)

References 42 publications

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“…A quantitative description of the motion of a sediment at a wall is quite difficult [71][72][73][74][75][76], and there are still many open questions. The following problems may be of relevance, but are beyond the scope of the present investigation: resuspension of particles [77,78] and related processes [79]; shear-induced migration of particles in concentrated suspensions [73][74][75]; not a sharp interface [80] and shear-induced corrugation of interfaces [81]; wall slip (depending on surface properties and particle material) [82][83][84][85][86][87][88][89]; stick-slip events [90]. For the present investigation, it is only of importance how the motion of the sediment affects the bulk flow, as this is what controls the settling time and the concentration in the suspension during the settling process.…”

Section: Iib: Sediment Moves Along the Wallmentioning

confidence: 99%

On basic equations and kinematic-wave theory of separation processes in suspensions with gravity, centrifugal and Coriolis forces

Schneider

2017

Acta Mech

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Neglecting inertial and viscosity effects in the bulk flow is a common assumption in the analysis of separation processes in suspensions under the action of gravity or centrifugal and Coriolis forces. While there is a number of examples of particular solutions, the general form of the basic equations for three space dimensions, together with the appropriate boundary and initial conditions, is still uncertain and, with regard to certain aspects, even controversial. An essential point is a proper choice of the variables. Here it is proposed to introduce the mass density of the mixture, the mean mass velocity of the mixture and the total volume flux as a set of dependent variables. After some manipulations, a complete set of basic equations is obtained. It consists of two continuity equations, a generalized drift-flux relation, and two linearly independent components of a vector equation describing the total body force as irrotational. Then, by eliminating the mean mass velocity of the mixture from the set of unknowns, a generalized kinematic-wave equation is derived. It describes kinematic waves that are embedded in a bulk flow that may be one-, two-or three-dimensional. Concerning boundary conditions at solid walls, one has to ascertain whether the total body force at the wall points into the suspension or out of it. In the former case, a thin boundary layer of clear liquid is formed at the wall, whereas in the latter case a thin sediment layer may either stick at the wall or slide along it. Each of those three possibilities leads to a particular boundary condition for the bulk flow in terms of the dependent variables. In addition, initial conditions and kinematic shock relations are briefly discussed. Finally, the application of the kinematic-wave theory to the settling process in rotating tubes is outlined.

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Section: Iib: Sediment Moves Along the Wallmentioning

confidence: 99%

On basic equations and kinematic-wave theory of separation processes in suspensions with gravity, centrifugal and Coriolis forces

Schneider

2017

Acta Mech

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“…Our results also show that a size polydispersity of up to 5% does not increase the jamming density significantly from the monodisperse case. A much larger dependence on the polydispersity is often used in the experiments [10] based on the results of Ref. [12], casting doubts on the precise values for the volume fractions determined in experiments via this route.…”

Section: Fig 1: A) Pressure βP σmentioning

confidence: 99%

“…Additionally, we give accurate data for the jamming density φ J as a function of compression rate and size polydispersity, which is important for experiments on colloidal systems. The packing fraction of a polydisperse colloidal system is often determined by setting the packing fraction of a centrifuged sediment [10] equal to the φ rcp obtained from simulations [11,12]. However, these simulation results are very inaccurate and do not take into account any compression rate dependence, casting doubts on the accuracy of the volume fractions determined in experiments via this route.…”

mentioning

confidence: 99%

Jamming of polydisperse hard spheres: The effect of kinetic arrest

Hermes¹,

Dijkstra²

2010

Europhys. Lett.

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We study jammed configurations of hard spheres as a function of compression speed using an event-driven molecular dynamics algorithm. We find that during the compression, the pressure follows closely the metastable liquid branch until the system gets arrested into a glass state as the relaxation time exceeds the compression speed. Further compression yields a jammed configuration that can be regarded as the infinite pressure configuration of that glass state. Consequently, we find that the density of jammed packings varies from 0.638 to 0.658 for polydisperse hard spheres and from 0.635 to 0.645 for pure hard spheres upon decreasing the compression rate. This demonstrates that the density at which the systems falls out of equilibrium determines the density at which the system jams at infinite pressure. In addition, we give accurate data for the jamming density as a function of compression rate and size polydispersity. [2] that the densest packing of identical hard spheres is achieved by the stacking of close-packed hexagonal planes yielding a packing fraction φ = πσ 3 N/6V ≈ 0.74. However, when a system of hard spheres is compressed quickly it does not reach this maximum density and it jams at lower densities. Jamming phenomena are generic since atomic, colloidal and granular systems can all be jammed in a state far out of equilibrium by quickly cooling, compressing or unloading [3].Many authors speculate that the packing fraction of the densest amorphous hard-sphere configuration is welldefined [4,5] although its precise value is not known as random-close-packing densities φ rcp ranging from 0.634 [5] to 0.648 [6] are reported. On the other hand, Torquato et al [7] argued that φ rcp is ill-defined as the density can always be increased by introducing crystalline order into the system. Very recently, it is speculated and/or deduced from mean-field models that jammed configurations can be regarded as the infinite pressure limit of glassy states [8,9]. The reason is that the glass phase for each density on the metastable fluid branch consists of a certain group of glassy states, which will all follow the same metastable glass branch up to the same jamming density by fast compression [8,9].In this letter, we study jammed configurations of hard spheres as a function of compression speed. We show that denser amorphous packings can be generated even without introducing any crystalline order by lowering the compression speed. However, in the case of identical spheres, the system (partially) crystallizes for sufficiently slow compressions. Crystallization can be avoided by introducing size polydispersity. A small size polydispersity affects φ rcp only slightly but hampers crystal growth severely. This allows us to study jamming for a wider range of compression rates. We find volume fractions ranging from 0.638 till 0.658 for hard spheres with 10% size polydispersity upon decreasing the compression rates. Additionally, we give accurate data for the jamming density φ J as a function of compression rate and size polydispe...

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“…The first group of designs uses counter-rotating surfaces to drive torsional flows with circular streamlines. 25,30,32,[35][36][37][38] Often, one of these surfaces is fixed in the laboratory frame. Independently rotating both surfaces, while more difficult, allows the zero-velocity plane to be moved away from the sample boundaries.…”

Section: Introductionmentioning

confidence: 99%

“…An alternate approach for torsional flows requires mounting a commercial rheometer on a confocal microscope. 25,[36][37][38] To achieve a uniform shear rate, commercial rheometers use a cone and plate geometry in which the sample thickness increases linearly with distance from the rotation axis. Measurements of confined suspensions, however, require a parallel plate geometry in which the sample thickness is uniform but the shear rate is not.…”

Section: Introductionmentioning

confidence: 99%

A multi-axis confocal rheoscope for studying shear flow of structured fluids

Lin

McCoy

Cheng

et al. 2014

Review of Scientific Instruments

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We present a new design for a confocal rheoscope that enables uniform uniaxial or biaxial shear. The design consists of two precisely positioned parallel plates with a gap that can be adjusted down to 2 ±0.1 μm, allowing for the exploration of confinement effects. By using our shear cell in conjunction with a biaxial force measurement device and a high-speed confocal microscope, we are able to measure the real-time biaxial stress while simultaneously imaging the material three-dimensional structure. We illustrate the importance of the instrument capabilities by discussing the applications of this instrument in current and future research topics in colloidal suspensions. © 2014 AIP Publishing LLC.[http://dx

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Slip and Flow of Hard-Sphere Colloidal Glasses

Cited by 106 publications

References 42 publications

On basic equations and kinematic-wave theory of separation processes in suspensions with gravity, centrifugal and Coriolis forces

On basic equations and kinematic-wave theory of separation processes in suspensions with gravity, centrifugal and Coriolis forces

Jamming of polydisperse hard spheres: The effect of kinetic arrest

A multi-axis confocal rheoscope for studying shear flow of structured fluids

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