A new interpretation of viscosity and yield stress in dense slurries: Coal and other irregular particles

Wildemuth, C. R.; Williams, Michael C.

doi:10.1007/bf01329266

Cited by 101 publications

(32 citation statements)

References 17 publications

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“…In this case, the authors attributed yielding behavior to either particle jams or weak polymer-particle interactions, but they did not provide quantitative justification in their explanations. Such behavior was also observed by Wildemuth and Williams [238] with coal-glycerin slurries, Kytömaa and Prasad [144,197] with 2 mm glass beads in a water-glycerol solution, Coussot [65] with 100 m polystyrene beads in water-glycerol solutions, and Johma et al [134] with 2 m polystyrene beads in water. In the latter case, the authors related the yield appearance to structural changes in the particle arrangement (glass transition) at a critical solid concentration (φ = 0.58).…”

Section: Constitutive Equations: Physical Origin Of the Yield Stressmentioning

confidence: 62%

Plasticity and geophysical flows: A review

Ancey

2007

Journal of Non-Newtonian Fluid Mechanics

345

277

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The objective of this review is to examine how the concept of plasticity is used in geophysical fluid dynamics. Rapid mass movements such as snow avalanches or debris flows involve slurries of solid particles (ice, boulder, clay, etc.) within an interstitial fluid (air, water). The bulk behavior of these materials has often been modeled as plastic materials, i.e., a plastic material yields and starts to flow once its stress state has significantly departed from equilibrium. Two plastic theories are of common use in fluid dynamics: Coulomb plasticity and viscoplasticity. These theories have little in common, since ideal Coulomb materials are two-phase materials for which pore pressure and friction play the key role in the bulk dynamics, whereas viscoplastic materials (e.g., Bingham fluids) typically behave as single-phase fluids on the macroscopic scale and exhibit a viscous behavior after yielding. Determining the rheological behavior of geophysical materials remains difficult because they encompass coarse, irregular particles over a very wide range of size. Consequently, the true nature of plastic behavior for geophysical flows is still vigorously debated. In this review, we first set out the continuum-mechanics principles used for describing plastic behavior. The notion of yield surface rather than yield stress is emphasized in order to better understand how tensorial constitutive equations can be derived from experimental data. The notion of single-phase or two-phase behaviors on the macroscopic scale is then examined using a microstructural analysis on idealized suspensions of spheres within a Newtonian fluid; for these suspensions, the single-phase approximation is valid only at very high or low Stokes numbers. Within this framework, the bulk stress tensor can also be constructed, which makes it possible to give a physical interpretation to yield stress. Most of the time, depending on the bulk properties (especially, particle size) and flow features, bulk behavior is either Coulomb-like or viscoplastic in simple-shear experiments. The consequences of the rheological properties on the flow features are also examined. Some remarkable properties of the governing equations describing thin layers flowing down inclined surfaces are discussed. Finally, the question of parameter fitting is tackled: since rheological properties cannot be measured directly in most cases, they must be evaluated from field data. As an example, we show that the Coulomb model successfully captures the main traits of avalanche motion, but statistical analysis demonstrates that the probability distribution of the friction coefficient is not universal.

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Section: Constitutive Equations: Physical Origin Of the Yield Stressmentioning

confidence: 62%

Plasticity and geophysical flows: A review

Ancey

2007

Journal of Non-Newtonian Fluid Mechanics

345

277

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“…Several authors have documented the existence of a yield stress in the limit of vanishing shear rate. [2][3][4] During the early attempts to model yield stress in non-colloidal systems, a popular idea was that the yield stress arises from the dependence of the maximum solid concentration on the shear stress. 2,5 Another explanation lies in the process of particle settling where frictional contacts between particles generate Coulomb friction on the bulk scale.…”

Section: Introductionmentioning

confidence: 99%

“…[2][3][4] During the early attempts to model yield stress in non-colloidal systems, a popular idea was that the yield stress arises from the dependence of the maximum solid concentration on the shear stress. 2,5 Another explanation lies in the process of particle settling where frictional contacts between particles generate Coulomb friction on the bulk scale. 6,7 Using magnetic resonance imaging, Ovarlez, Bertrand, and Rodts 8 measured the velocity and concentration profiles inside a wide-gap coaxial-cylinder rheometer.…”

Section: Introductionmentioning

confidence: 99%

Granular suspension avalanches. II. Plastic regime

2013

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We present flume experiments showing plastic behavior for perfectly density-matched suspensions of non-Brownian particles within a Newtonian fluid. In contrast with most earlier experimental investigations (carried out using coaxial cylinder rheometers), we obtained our rheological information by studying thin films of suspension flowing down an inclined flume. Using particles with the same refractive index as the interstitial fluid made it possible to measure the velocity field far from the wall using a laser-optical system. At long times, a stick-slip regime occurred as soon as the fluid pressure dropped sufficiently for the particle pressure to become compressive. Our explanation was that the drop in fluid pressure combined with the surface tension caused the flow to come to rest by significantly increasing flow resistance. However, the reason why the fluid pressure diffused through the pores during the stick phases escaped our understanding of suspension rheology. C 2013 American Institute of Physics. [http://dx

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“…They observed that this yield stress increased dramatically when the solid concentration approached its densest packing. Ancey [1] mentions other supporting evidences for such a yield stress and quotes Wildemuth and Williams' [44] yield stress formula…”

Section: Viscous Stress Parameterization Based On Viscometric Considementioning

confidence: 96%

Important aspects in the formulation of solid–fluid debris-flow models. Part II. Constitutive modelling

Hutter¹,

Schneider²

2010

Continuum Mech. Thermodyn.

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The intention is to see whether (i) well-known formulations of binary mixture models can be derived from the thermodynamic model, (ii) classical hypo-plasticity is deducible from the frictional evolution equation and (iii) the popular assumption of pressure equilibrium is justified. To this end, we ignore mass and volume fraction interaction rate densities, restrict considerations to isothermal processes, ignore higher order non-linearities in the constitutive relations and use the principle of phase separation. These assumptions transform the equilibrium stresses, heat flux and interaction forces to considerably simplified forms. Furthermore, the analysis shows that classical hypo-plasticity can be reconstructed with the introduction of a new objective time derivative for the stress-like variable. Non-equilibrium contributions to the stresses and interaction forces are also briefly discussed. It is, finally, shown that the assumption of pressure equilibrium precludes the application of frictional stresses in equilibrium. This unphysical assumption is, therefore, replaced by a thermodynamic closure condition that is more flexible and less restrictive. It allows for frictional stresses in thermodynamic equilibrium and, therefore, is sufficiently general for applications to mixture theories.

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A new interpretation of viscosity and yield stress in dense slurries: Coal and other irregular particles

Cited by 101 publications

References 17 publications

Plasticity and geophysical flows: A review

Plasticity and geophysical flows: A review

Granular suspension avalanches. II. Plastic regime

Important aspects in the formulation of solid–fluid debris-flow models. Part II. Constitutive modelling

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