The effect of particle size distribution on the antithixotropic and shear thickening properties of coal–water dispersions

Keller, D. Steven; Keller, Donald V.

doi:10.1122/1.550246

Cited by 32 publications

(17 citation statements)

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“…The fact that φ/φ c acts as the control parameter for the strength of Discontinuous Shear Thickening has several consequences. It suggests that the apparent weakening of shear thickening for more spherical shapes [12] or more polydisperse sizes [30] at constant φ can be explained by the fact that φ c is moved further away. Similarly, particles that form fractal aggregates have been found to exhibit Discontinuous Shear Thickening at packing fractions as low as 11%, which is not surprising in this interpretation since they also pack at very low densities [31].…”

Section: Discussionmentioning

confidence: 99%

Shear thickening and jamming in densely packed suspensions of different particle shapes

et al. 2011

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We investigated the effects of particle shape on shear thickening in densely packed suspensions. Rods of different aspect ratios and nonconvex hooked rods were fabricated. Viscosity curves and normal stresses were measured using a rheometer for a wide range of packing fractions for each shape. Suspensions of each shape exhibit qualitatively similar discontinuous shear thickening. The logarithmic slope of the stress vs shear rate increases dramatically with packing fraction and diverges at a critical packing fraction φ(c) which depends on particle shape. The packing fraction dependence of the viscosity curves for different convex shapes can be collapsed when the packing fraction is normalized by φ(c). Intriguingly, viscosity curves for nonconvex particles do not collapse on the same set as convex particles, showing strong shear thickening over a wider range of packing fraction. The value of φ(c) is found to coincide with the onset of a yield stress at the jamming transition, suggesting the jamming transition also controls shear thickening. The yield stress is found to correspond with trapped air in the suspensions, and the scale of the stress can be attributed to interfacial tension forces which dramatically increase above φ(c) due to the geometric constraints of jamming. Using this connection we show that the jamming transition can be identified by simply looking at the surface of suspensions. The relationship between shear and normal stresses is found to be linear in both the shear thickening and jammed regimes, indicating that the shear stresses come from friction. In the limit of zero shear rate, normal stresses pull the rheometer plates together due to the surface tension of the liquid below φ(c), but push the rheometer plates apart due to jamming above φ(c).

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Section: Discussionmentioning

confidence: 99%

Shear thickening and jamming in densely packed suspensions of different particle shapes

et al. 2011

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“…Their rheology is the topic of this letter.Understanding the rheological properties of non-Brownian suspensions is not only a challenge from a theoretical point of view [5][6][7] but has also a significant impact in many industrial applications, e.g. oil processing, cement or coal slurries [8,9].In one of the earliest work in this field, Einstein showed that for a dilute suspension of rigid particles in a Newtonian fluid with negligible inertia the relative increase in effective viscosity is ∼ (5/2)φ where φ is the volume fraction occupied by the particles [see e.g., 10, chapter 4.11]. For higher concentrations the problem is still not well understood.…”

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confidence: 99%

Shear Thickening in Non-Brownian Suspensions: An Excluded Volume Effect

et al. 2013

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Shear thickening appears as an increase of the viscosity of a dense suspension with the shear rate, sometimes sudden and violent at high volume fraction. Its origin for noncolloidal suspension with non-negligible inertial effects is still debated. Here we consider a simple shear flow and demonstrate that fluid inertia causes a strong microstructure anisotropy that results in the formation of a shadow region with no relative flux of particles. We show that shear thickening at finite inertia can be explained as an increase of the effective volume fraction when considering the dynamically excluded volume due to these shadow regions.

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“…Barnes (1989) reported that the severity of shear thickening depends, among other factors, on the shape of the granule size distribution. Keller Keller (1991) and Boersma et al (1990) reported decrease in shear thickening effects in polydisperse in comparison with monodisperse dispersions of rigid particles. However, as gelatinization progresses starch granules swell and their deformability increases.…”

Section: Steady Shear Data Figuresmentioning

confidence: 99%

Granule Size Distribution and Rheological Behavior of Heated Modified Waxy and Unmodified Maize Starch Dispersions

Oliveira

Rao

1997

Journal of Texture Studies

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The effect of granule size distribution, supported by microscopic analysis, on the steady shear and dynamic shear rheological behavior of 5% gelatinized modified waxy maize starch (MWMS) dispersions heated at 80C for time periods from 0.5 to 30 min was examined and data obtained with 5% unmodified maize starch (UMS) dispersions was used to provide additional insight. The MWMS dispersions showed a faster and more extensive swelling than the UMS dispersions at 80C. They also exhibited rheopectic (anti‐thixotropic) time‐dependent and shear thinning with yield stress behavior. UMS dispersions showed shear thickening characteristics after short heating times that gradually turned to shear thinning as the heating time was increased. Dynamic tests on MWMS dispersions showed G’ was about ten times higher than G″. G′ showed a small dependence on frequency over 0.6–63 rad/s while G”, after an increase at low frequencies, became less sensitive. The gelatinized MWMS dispersions can therefore be classified as ‘weak gels.’ The flow behavior index of UMS dispersions was strongly

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The effect of particle size distribution on the antithixotropic and shear thickening properties of coal–water dispersions

Cited by 32 publications

References 0 publications

Shear thickening and jamming in densely packed suspensions of different particle shapes

Shear thickening and jamming in densely packed suspensions of different particle shapes

Shear Thickening in Non-Brownian Suspensions: An Excluded Volume Effect

Granule Size Distribution and Rheological Behavior of Heated Modified Waxy and Unmodified Maize Starch Dispersions

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