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
Shear thickening of cornstarch suspensions
TL;DR: In this paper, the authors studied the rheology of cornstarch suspensions, a non-Brownian particle system that exhibits discontinuous shear thickening, and found that the shear region of a nonflowing region seems to prevent or delay shear thinning.
Journal ArticleDOI
Exponential formula for computing effective viscosity.
TL;DR: In this article, an exponential model is proposed for evaluating the effective viscosity of a particle-fluid mixture, which is restricted to the dilute condition without effects of dynamic particle interactions and fluid turbulence.
Journal ArticleDOI
A review of membrane bioreactor potential for nitrate removal from drinking water
Ewan J. McAdam,Simon J. Judd +1 more
TL;DR: In this paper, the authors present a review of the research to date appraising advantages and disadvantages associated with each configuration whilst also identifying areas that require further research and consequently assessing which nitrate removal MBR technologies will prevail for the future.
Journal ArticleDOI
Complexity, segregation, and pattern formation in rotating-drum flows
Gabriel Seiden,Peter J. Thomas +1 more
TL;DR: The literature related to rotating-drum flows is reviewed in this paper, highlighting similarities and differences between the various flow realizations, and placing an emphasis on pattern formation phenomena, such as reversible transitions and hysteresis.
Journal ArticleDOI
Spreading of the interface at the top of a slightly polydisperse sedimenting suspension
Robert H. Davis,Mark A. Hassen +1 more
TL;DR: In this article, a light extinction technique was used to measure the concentration profile in the interface of a suspension of particles with a small spread of sizes as it fell past a thin sheet of light, and the measured vertical thickness of the interface was found to be several times that predicted from this theory.
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.