Journal ArticleDOI
The shear-induced migration of particles in concentrated suspensions
TLDR
In this article, it was shown that shear-induced migration of particles out of the sheared Couette gap and into the fluid reservoir, which reduces the particle concentration in the gap and thereby the observed viscosity, is consistent with a gap-limited shearinduced diffusion process normal to the plane of shear, with the relevant diffusion coefficient being proportional to the applied shear rate.Abstract:
In the course of viscometric measurements of concentrated suspensions of spheres in Newtonian fluids using a Couette device, Gadala-Maria & Acrivos (1980) observed a decrease in the suspension viscosity after long periods of shearing even though the viscosity of the pure suspending fluid remained constant under identical conditions. In the present work we demonstrate that this phenomenon is due to the shear-induced migration of particles out of the sheared Couette gap and into the fluid reservoir, which reduces the particle concentration in the gap and thereby the observed viscosity. We show further that this rate of viscosity decrease is consistent with a gap-limited shear-induced diffusion process normal to the plane of shear, with the relevant diffusion coefficient being proportional to is the applied shear rate.Additional experiments also uncovered a new phenomenon - a short-term increase in the viscosity upon initial shearing of a suspension in a Couette device - which was attributed to the diffusive migration of particles across the width of the Couette gap and thus was used to infer values of the corresponding diffusion coefficient within the plane of shear parallel to gradients in fluid velocity.In the theoretical part we demonstrate that the particle migrations that led to these observed phenomena may be explained in terms of the irreversible interparticle interactions that occur in these suspensions. From simple arguments, these interactions are shown to lead to effective diffusivities both normal to the plane of shear and normal to the direction of fluid motion within the plane of shear whose estimated magnitudes are comparable with those that were inferred from the experimental measurements. Furthermore, these interactions should induce, within a shear flow, particle drifts from regions of high to low shear stress, which are estimated to be of sufficient intensity to account for the observed initial viscosity increase mentioned above.read more
Citations
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Journal ArticleDOI
Collapse of a neutrally buoyant suspension column: from Newtonian to apparent non-Newtonian flow regimes
TL;DR: In this article, the Krieger-Dougherty model was used to study the dynamics of a cascade of noncolloidal and neutrally buoyant particles suspended in a Newtonian fluid column, in which the initial volume fraction of the suspension Phi, the viscosity of the interstitial fluid Muf, the diameter of the particles d and the mixing protocol, i.e. the initial preparation of the suspensions, are varied.
Journal ArticleDOI
Shear dispersion in dense granular flows
TL;DR: In this paper, the authors formulated and solved a model problem of dispersion of dense granular materials in rapid shear flow down an incline, and the effective dispersivity of the depth-averaged concentration of the dispersing powder was shown to vary as the Peclet number squared.
Dissertation
Dead-end and crossflow microfiltration of yeast and bentonite suspensions: experimental and modelling studies incorporating the use of artificial neural networks
TL;DR: In this paper, the applicability of artificial neural networks (ANNs) and semi-empirical modelling techniques for correlation and prediction of the filtration characteristics of microfiltration systems was assessed.
Journal ArticleDOI
Numerical simulation of coupled cell motion and nutrient transport in NASA’s rotating bioreactor
TL;DR: A numerical model of suspended particle motion is used to simulate the cell motion and distribution in a specific variant of the NASABioreactor, namely, the high aspect ratio vessel (HARV) bioreactor to help optimise the culture conditions for the cells in HARV bioreactors.
Journal ArticleDOI
The effects of proppant on the near-front behavior of a hydraulic fracture
TL;DR: In this paper, the qualitative and quantitative effects of proppant on the near front region of a hydraulic fracture were investigated by solving the problem of a semi-infinite fracture driven by a slurry of Newtonian fluid with proppants.
References
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Journal ArticleDOI
Inertial migration of rigid spheres in two-dimensional unidirectional flows
B. P. Ho,L. G. Leal +1 more
TL;DR: In this article, the Segre-Silberberg effect of inertia-induced lateral migration of a neutrally buoyant rigid sphere in a Newtonian fluid is studied theoretically for simple shear flow and for two-dimensional Poiseuille flow.
Journal ArticleDOI
Shear‐Induced Structure in a Concentrated Suspension of Solid Spheres
TL;DR: In this article, a Couette device of a R•17 Weissenberg Rheogoniometer with suspensions of polystyrene spheres, 40-50 μm in diameter, suspended in a mixture of silicone oils at volume fractions 0⩽φ0.55 was used for steady and transient shear measurements.
Journal ArticleDOI
Measurement of shear-induced self-diffusion in concentrated suspensions of spheres
TL;DR: In this paper, a technique for determining the coefficient of shear-induced particle self-diffusion in concentrated suspensions of solid spheres, which relies on the fact that this coefficient can be computed from the measured variations in the time taken by a single marked particle in the suspension to complete successive circuits in a Couette device, was presented.
Journal ArticleDOI
Self-diffusion of particles in shear flow of a suspension
TL;DR: In this paper, a self-diffusion coefficient for lateral dispersion of spherical and disk-like particles in linear shear flow of a slurry at very low Reynolds number was determined experimentally.
Journal ArticleDOI
The kinetics of flowing dispersions
TL;DR: In this article, the velocity profiles of dilute suspensions of rigid spheres in Newtonian liquids undergoing Couette or Poiseuille flow were found to be identical with those predicted by the theory with no particles present.