Slip Effects in Capillary and Parallel Disk Torsional Flows of Highly Filled Suspensions

Yilmazer, Ülkü; Kalyon, Dilhan M.

doi:10.1122/1.550049

Cited by 239 publications

(118 citation statements)

References 6 publications

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“…Plug flow and wall slip have been observed in a number of other experiments on concentrated dispersions. However, these observations were mainly done in capillary flows (Yilmazer and Kalyon, 1989).…”

Section: Comparison With Previously Reported Resultsmentioning

confidence: 99%

Time‐dependent behavior and wall slip in concentrated shear thickening dispersions

Boersma

Baets

Lavèn

et al. 1991

Journal of Rheology

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SynopsisThe viscosity of concentrated shear thickening dispersions was measured as a function of shear rate, Couette cylinder size, and time. The level of the low shear rate viscosity, which was found to be independent of system size and time, could bc predicted by the equation of Frankel and Acrivos. At shear rates above the critical shear rate for shear thickening in highly concentrated (#> 0.57) dispersions of monodispcrse particles strong viscosity instabilities were detected, together with a dependence on cylinder size. The instabilities are attributed to reversible order-disorder transitions, e.g., from strings to clusters. This dependence on cylinder size is due to wall slip, slipping planes in the dispersion, and even plug flow in the gap. With less concentrated or polydisperse dispersions the effects are much less severe but there is thixotropy, probably due to a reordering of the dispersion.

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Section: Comparison With Previously Reported Resultsmentioning

confidence: 99%

Time‐dependent behavior and wall slip in concentrated shear thickening dispersions

Boersma

Baets

Lavèn

et al. 1991

Journal of Rheology

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“…This slip is most apparent with smooth walls; 35,36 it may lead to an erroneous mixture viscosity if a correction is not applied. 3 Experiments have shown that the slip is significantly reduced when the surface roughness is the same size as or larger than the diameter of the particles.…”

Section: -9mentioning

confidence: 99%

Rheological measurements of large particles in high shear rate flows

et al. 2012

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How to impose stick boundary conditions in coarse-grained hydrodynamics of Brownian colloids and semiflexible fiber rheology J. Chem. Phys. 136, 064901 (2012) This paper presents experimental measurements of the rheological behavior of liquid-solid mixtures at moderate Stokes and Reynolds numbers. The experiments were performed in a coaxial rheometer that was designed to minimize the effects of secondary flows. By changing the shear rate, particle size, and liquid viscosity, the Reynolds numbers based on shear rate and particle diameter ranged from 20 to 800 (Stokes numbers from 3 to 90), which is higher than examined in earlier rheometric studies. Prior studies have suggested that as the shear rate is increased, particleparticle collisions also increase resulting in a shear stress that depends non-linearly on the shear rate. However, over the range of conditions that were examined in this study, the shear stress showed a linear dependence on the shear rate. Hence, the effective relative viscosity is independent of the Reynolds and Stokes numbers and a nonlinear function of the solid fraction. The present work also includes a series of roughwall experiments that show the relative effective viscosity is also independent of the shear rate and larger than in the smooth wall experiments. In addition, measurements were made of the near-wall particle velocities, which demonstrate the presence of slip at the wall for the smooth-walled experiments. The depletion layer thickness, a region next to the walls where the solid fraction decreases, was calculated based on these measurements. The relative effective viscosities in the current work are larger than found in low-Reynolds number suspension studies but are comparable with a few granular suspension studies from which the relative effective viscosities can be inferred.

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“…The usual explanation for apparent wall slip is that spherical particles cannot pack as efficiently by a solid surface as in the bulk, and accordingly a lower effective particle volume fraction exists near the surface, which leads to a low resistance layer near the surface (Yilmazer and Kalyon, 1989;Jana et al, 1995). Wall slip is an observable phenomenon in standard rheometry and typically causes unexpectedly low viscosity readings and viscosity readings that are extremely sensitive to the roughness of the solid shearing surfaces.…”

Section: Monodisperse Spheresmentioning

confidence: 99%

Laser Doppler velocimetry measurements of particle velocity fluctuations in a concentrated suspension

Shapley

Armstrong

Brown

2002

Journal of Rheology

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Recent statistical constitutive models of suspensions of neutrally buoyant, non-Brownian, noncolloidal, solid spheres in Newtonian fluids suggest that the particles nijgrate in response to gradients in "suspension temperature," defined as the average kinetic energy contained in the particle velocity fluctuations. These models have not yet been compared systematically with experimental data.In addition, the "temperature" models assume isotropic particle velocity fluctuations, since the "suspension temperature" is given as a scalar, in analogy to molecular systems. However, highly anisotropic particle velocity fluctuations have been observed in settling suspensions, which suggests that a "suspension temperature" tensor would be more realistic.We used laser Doppler velocimetry (LDV) to make a set of experimental observations of particle velocity fluctuations arising from inter-particle collisions in a concentrated non-colloidal suspension under nearly homogeneous shear flow in a narrow-gap concentric cylinder Couette device. We compared the relative sizes of the fluctuating velocity components and observed the variation of each component with particle volume fraction, shear rate, and radial position. In addition, we assessed the implications of these observations for suspension temperature models.The data indicate that the suspension temperature is anisotropic. The flow direction component is overwhelmingly the largest at every concentration and shear rate, followed by the neutral and then the gradient components. Meanwhile, each fluctuating velocity component demonstrates a distinct variation with the shear rate and with the particle volume fraction, but only slight variation with radial position, over the region of the flow accessible to measurement.Comparison between model predictions and measured shear rate and particle volume fraction profiles shows that several models capture the measured profiles qualitatively but not quantitatively, with better agreement for moderately concentrated suspensions than for highly concentrated suspensions. Also, comparison between predicted scalar suspension temperature profiles and the sum of the measured velocity fluctuation components demonstrates that most of the models underpredict the sum of the temperature components by a large factor. Finally, comparison among the models shows that the models are quite sensitive to the choice of transport coefficients that are functions of the particle volume fraction.

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Slip Effects in Capillary and Parallel Disk Torsional Flows of Highly Filled Suspensions

Cited by 239 publications

References 6 publications

Time‐dependent behavior and wall slip in concentrated shear thickening dispersions

Time‐dependent behavior and wall slip in concentrated shear thickening dispersions

Rheological measurements of large particles in high shear rate flows

Laser Doppler velocimetry measurements of particle velocity fluctuations in a concentrated suspension

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