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
More filters
Journal ArticleDOI
Prediction of thickener performance with aggregate densification
TL;DR: In this paper, the effects of densification on the bed heights and on the solids residence times required to achieve a given underflow solids flux and a given Underflow Solids volume fraction were also computed and compared.
Journal ArticleDOI
Numerical Prediction on the Effects of the Coarse Aggregate Size to the Pipe Flow of Pumped Concrete
TL;DR: In this paper, a method to improve the properties of the lubrication layer was suggested by imposing ultrasound on the pipe, and three different intensities of ultrasonic energy were applied while conducting 170 m long full scale pumping tests.
Journal ArticleDOI
Visualization of the flow of a fiber suspension through a sudden expansion using PET
TL;DR: In this article, the motion of 18F radioactively labeled papermaking fibers flowing through an axisymmetric 1:5 sudden expansion has been studied using positron emission tomography (PET).
Journal ArticleDOI
Theory of suspension segregation in partially filled horizontal rotating cylinders
TL;DR: In this article, it was shown that a suspension of particles in a partially-filled, horizontal, rotating cylinder is linearly unstable towards axial segregation and an undulation of the free surface at large enough particle concentrations.
Journal ArticleDOI
Experimental investigation of the flow dynamics and rheology of complex fluids in pipe flow by hybrid multi-scale velocimetry
Sanna Haavisto,Maria Cardona,Juha Salmela,Robert L. Powell,Michael J. McCarthy,Markku Kataja,Antti Koponen +6 more
TL;DR: In this article, a hybrid multi-scale velocimetry method utilizing Doppler optical coherence tomography in combination with either magnetic resonance imaging or ultrasound velocity profiling is used to investigate pipe flow of four rheologically different working fluids under varying flow regimes.
References
More filters
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.