scholarly journals Fully developed and transient concentration profiles of particulate suspensions sheared in a cylindrical Couette cell

2019 ◽  
Vol 862 ◽  
pp. 659-671 ◽  
Author(s):  
Mohammad Sarabian ◽  
Mohammadhossein Firouznia ◽  
Bloen Metzger ◽  
Sarah Hormozi
Keyword(s):  
Volume Fraction ◽  
Particle Migration ◽  
Balance Model ◽  
Concentration Profiles ◽  
Particulate Suspensions ◽  
Index Matching ◽  
Bulk Volume ◽  
Taylor Couette ◽  
Particulate Volume Fraction ◽  
Matching Techniques

We experimentally investigate particle migration in a non-Brownian suspension sheared in a Taylor–Couette configuration and in the limit of vanishing Reynolds number. Highly resolved index-matching techniques are used to measure the local particulate volume fraction. In this wide-gap Taylor–Couette configuration, we find that for a large range of bulk volume fraction, $\unicode[STIX]{x1D719}_{b}\in [20\,\%{-}50\,\%]$, the fully developed concentration profiles are well predicted by the suspension balance model of Nott & Brady (J. Fluid Mech., vol. 275, 1994, pp. 157–199). Moreover, we provide systematic measurements of the migration strain scale and of the migration amplitude which highlight the limits of the suspension balance model predictions.

Dynamics of shear-induced migration of spherical particles in oscillatory pipe flow

2015 ◽  
Vol 786 ◽  
pp. 128-153 ◽  
Author(s):  
Braden Snook ◽  
Jason E. Butler ◽  
Élisabeth Guazzelli
Keyword(s):  
Volume Fraction ◽  
Particle Volume Fraction ◽  
Spherical Particles ◽  
Balance Model ◽  
Particle Volume ◽  
Lower Shear ◽  
Index Matching ◽  
Lower Shear Rate ◽  
Refractive Index Matching ◽  
Matching Techniques

The large-amplitude oscillatory flow of a suspension of spherical particles in a pipe is studied at low Reynolds number. Particle volume fraction and velocity are examined through refractive index matching techniques. The particles migrate toward the centre of the pipe, i.e. toward regions of lower shear rate, for bulk volume fractions larger than 10 %. Steady results are in agreement with available experimental results and discrete-particle simulations for similar geometries. The dynamics of the shear-induced migration process are analysed and compared against the predictions of the suspension balance model using realistic rheological laws.

An experimental study of the motion of concentrated suspensions in two-dimensional channel flow. Part 2. Bidisperse systems

1998 ◽  
Vol 363 ◽  
pp. 57-77 ◽  
Author(s):  
M. K. LYON ◽  
L. G. LEAL
Keyword(s):  
Large Particle ◽  
Particle Concentration ◽  
Volume Fraction ◽  
Balance Model ◽  
Concentration Profiles ◽  
Size Segregation ◽  
Small Particles ◽  
Concentrated Suspensions ◽  
Particle Volume ◽  
Large Particles

In this paper we report experimental velocity and concentration profiles for suspensions possessing a bidisperse distribution of particle size undergoing pressure-driven flow through a parallel-wall channel. In addition to the overall concentration distributions determined by implementing the modified laser Doppler velocimetry method described in Part 1 (Lyon & Leal 1998), concentration profiles for the particles of each size were measured by sampling the position of marked tracer particles across 60% of the channel gap. Non-uniform overall particle concentration distributions and blunted velocity profiles were found at bulk particle volume fractions of 0.30 and 0.40, which were equal to the monodisperse data of Part 1, within experimental uncertainty. The large-particle concentration profiles were non-uniform down to a large-particle bulk volume fraction of 0.075, while non-uniform distributions of the small particles were only found when the volume fraction of small particles in the bulk was greater than or equal to 0.20. Experiments in which at least half the suspended particulate volume was occupied by large particles revealed enrichment of the large particles in the centreline region of the channel. This size segregation was found to increase as the total number of suspended particles decreased. Finally, the data from experiments in which a uniform small-particle concentration profile was measured were compared with suspension balance model (McTigue & Jenkins 1992; Nott & Brady 1994) predictions for parameter values that corresponded only to the large particles. While close agreement with the large-particle concentration profiles was found, this comparison also reflected the fact that the small particles bring the suspension viscosity to a regime that is more sensitive to the particle concentration, rather than simply providing an increment in background viscosity to the suspending liquid.

Dense suspensions in rotating-rod flows: normal stresses and particle migration

2011 ◽  
Vol 686 ◽  
pp. 5-25 ◽  
Author(s):  
François Boyer ◽  
Olivier Pouliquen ◽  
Élisabeth Guazzelli
Keyword(s):  
Shear Rate ◽  
Normal Stress ◽  
Volume Fraction ◽  
Particle Migration ◽  
Balance Model ◽  
Normal Stresses ◽  
Dense Suspensions ◽  
Normal Stress Differences ◽  
Neutrally Buoyant ◽  
Dependent Behaviour

AbstractNormal stress differences are measured in dense suspensions of neutrally buoyant non-Brownian spheres dispersed in a Newtonian fluid. Rotating-rod rheometry is used to characterize the suspension normal stresses which are responsible for a rod-dipping phenomenon. These normal stress differences are seen to strongly increase above a volume fraction of approximately 22 %. During the course of the experiments, a new time-dependent behaviour is also observed: the dip is filled with increasing times. This time evolution is found to be related to particle migration from regions of high shear rate to regions of low shear rate. The behaviour is compared with the predictions of a suspension balance model in which the particle migration flux is related to the normal stresses of the suspension.

Microstructure and Mechanical Properties of In Situ TiB2/6061 Composites

2012 ◽  
Vol 535-537 ◽  
pp. 14-17
Author(s):  
Long Hua Zhong ◽  
Yu Tao Zhao ◽  
Song Li Zhang ◽  
Rong Wen
Keyword(s):  
Master Alloy ◽  
Volume Fraction ◽  
X Ray Diffraction ◽  
Melt Mixing ◽  
X Ray ◽  
Mixing Method ◽  
Particulate Volume Fraction ◽  
Ti Powder ◽  
Particulate Volume

In situ TiB2/6061 composites have been successfully synthesized through chemical reaction between 6061 master alloy, Al-3B master alloy and Ti powder. The composites fabricated by direct melt mixing method was investigated by Scanning Electron Microscope (SEM), Energy Dispersive x-ray Spectroscopy (EDS) and X-Ray Diffraction (XRD), The results shown the existence of TiB2particles. The size of most TiB2particles were just in micron level, and even reached to sub-micron level. The increase in microhardness and tensile strength for the as-prepared composites with 5% particulate volume fraction (PVF) are up to 26.8% and 51.2% respectively.

scholarly journals Sedimentation in flocculating colloidal suspensions

1994 ◽  
Vol 9 (2) ◽  
pp. 451-461 ◽  
Author(s):  
Jeffrey S. Abel ◽  
Gregory C. Stangle ◽  
Christopher H. Schilling ◽  
Ilhan A. Aksay
Keyword(s):  
Gamma Ray ◽  
Volume Fraction ◽  
Particle Volume Fraction ◽  
Colloidal Suspensions ◽  
Balance Model ◽  
Suspension Stability ◽  
Particle Volume ◽  
Sedimentation Behavior ◽  
Model Predictions ◽  
Ceramic Suspensions

A combined experimental and theoretical investigation of the sedimentation of unstable colloidal ceramic suspensions has been performed. Suspensions containing submicron-sized α-Al2O3 particles were prepared at various pH values in order to modify suspension stability. Particle volume fraction during sedimentation was determined as a function of position and time by gamma-ray densitometry. A population balance model was developed to account for various coagulation and decoagulation mechanisms that affect sedimentation behavior in flocculating suspensions. Model predictions were then compared with experimental measurements, in order to establish the validity of the theoretical model.

Heat transfer and shear-induced migration in dense non-Brownian suspension flows: modelling and simulation

2018 ◽  
Vol 840 ◽  
pp. 432-454 ◽  
Author(s):  
T. Dbouk
Keyword(s):  
Heat Transfer ◽  
Thermal Diffusivity ◽  
Shear Rate ◽  
Volume Fraction ◽  
Particle Volume Fraction ◽  
Laminar Flows ◽  
Modelling And Simulation ◽  
Particle Migration ◽  
Concentrated Suspension ◽  
Suspension Flows

Modelling and simulation are developed, generalized and validated for both heat transfer and shear-induced particle migration in dense non-colloidal laminar suspension flows. Past theory and measurements for the effective thermal conductivity in porous materials at zero shear rate are coupled to more recent effective thermal diffusivity measurements of sheared suspensions. The suspension effective heat transfer affected by the local shear rate ($\dot{\unicode[STIX]{x1D6FE}}$), the phenomenon of shear-induced particle migration (SIM), the buoyancy effects ($\unicode[STIX]{x0394}\unicode[STIX]{x1D70C}$) and the thermal Péclet number ($Pe_{d_{p}}=\dot{\unicode[STIX]{x1D6FE}}d_{p}^{2}/\unicode[STIX]{x1D6FC}_{f}$, where $d_{p}$ is the diameter of rigid particles and $\unicode[STIX]{x1D6FC}_{f}$ is the fluid phase thermal diffusivity) at the particle scale are all considered in the present constitutive three-dimensional modelling. Moreover, the influence of the temperature, the shear rate and the particle volume fraction ($\unicode[STIX]{x1D719}$) on the suspension effective viscosity ($\unicode[STIX]{x1D702}_{S}$), the suspension effective thermal properties and the fluid density ($\unicode[STIX]{x1D70C}_{f}$) are taken also into account. The present contribution represents an emerging field of heat transfer applications of complex fluid flows and is very beneficial for many future applications where concentrated suspension laminar flows with conjugate heat transfer may be present (e.g. for designing more innovative and compact heat exchangers).

scholarly journals Experimental Insights into Concrete Flow-Regimes Subject to Shear-Induced Particle Migration (SIPM) during Pumping

Materials ◽  
2020 ◽  
Vol 13 (5) ◽  
pp. 1233 ◽  
Author(s):  
Shirin Fataei ◽  
Egor Secrieru ◽  
Viktor Mechtcherine
Keyword(s):  
Flow Pattern ◽  
Volume Fraction ◽  
Discharge Rate ◽  
High Volume ◽  
Particle Migration ◽  
Hardened Concrete ◽  
Concrete Pipe ◽  
Lubricating Layer ◽  
Definition Of ◽  
Concrete Flow

In this paper, the authors have focused on shear-induced particle migration (SIPM), its effect on concrete flow patterns, and lubricating layer formation during pumping. For this purpose, various volume-fractions ϕ of aggregates were selected. The particle migration was analyzed by applying two methods: sampling hardened concrete exposed to pumping and performing X-ray microcomputed tomography (μCT) and image analysis to determine the thickness of the lubricating layer due to SIPM. The results indicate that the first approach is unsuitable due to the nearly equal molecular density of particles and matrix. The second approach indicated that the actual thickness of the lubricating layer depends on the discharge rate as well as on ϕ and viscosity of concrete bulk; hence, it cannot be defined as a constant parameter for all concrete mixtures. Additionally, the concrete pipe-flow pattern, i.e., plug versus shear flow, was captured and studied while considering pumping pressure and discharge rate. It was concluded that particle migration is essential in the cases of both flowable and very flowable concretes with a high volume-fraction of solids. The changes in rheological properties caused by SIPM are severe enough to influence the definition of the flow pattern as plug or shear and the discharge rate of pumped concrete as well.

Modelling Flocculated Cell Suspensions using a Population Balance Approach: Applications to Microfiltration

2002 ◽  
Vol 752 ◽  
Author(s):  
S. Ranil Wickramasinghe ◽  
Binbing Han ◽  
Saengchai Akeprathumchai ◽  
Xianghong Qian
Keyword(s):  
Distribution Function ◽  
Size Distribution ◽  
Volume Fraction ◽  
Particle Diameter ◽  
Population Balance ◽  
Balance Model ◽  
Floc Size ◽  
Balance Approach ◽  
Fragment Distribution ◽  
Log Normal

ABSTRACTExperimental results for flocculation of yeast and CHO cells using cationic polyelectrolytes are presented. These results suggest the existence of a self-similar floc size distribution. The experimentally determined floc size distributions have been modelled using a population balance approach. For flocculated yeast suspensions, the variation of the floc volume fraction with dimensionless particle diameter is predicted by the population balance model assuming a binary fragment distribution function. However, for CHO cell flocs, the floc volume fraction is predicted using a log normal fragment distribution function. Since the efficiency of unit operations such as microfiltration may be improved by flocculation of the feed suspension characterization of the particle size distribution is of great importance.

Computational Study of Slurry Flow in Pipes to Determine Profiles Sensed in Near Infrared Slurry Measurements

2011 ◽  
Author(s):  
V. Pasangulapati ◽  
N. R. Kesana ◽  
G. Sharma ◽  
F. W. Chambers ◽  
M. E. McNally ◽  
...  
Keyword(s):  
Near Infrared ◽  
Volume Fraction ◽  
Solid Phase ◽  
Computational Study ◽  
Solid Volume Fraction ◽  
Density Ratio ◽  
Optical Measurements ◽  
Concentration Profiles ◽  
Horizontal Pipe ◽  
Volume Fractions

It is desired to perform accurate Near Infrared sensor measurements of slurries flowing in pipes leaving large batch reactors. A concern with these measurements is the degree to which the slurry sensed is representative of the material in the reactor and flowing through the pipe. Computational Fluid Dynamics (CFD) has been applied to the flow in the pipe to determine the flow fields and the concentration profiles seen by the sensors. The slurry was comprised of a xylene liquid phase and an ADP (2-amino-4, 6-dimethylpyrimidine) solid phase with a density ratio of 1.7. Computations were performed for a horizontal pipe with diameter 50.8 mm, length 2.032 m, and 1.76 m/s and 3.26 m/s mixture velocities. The corresponding pipe Reynolds numbers were 1.19E+05 and 2.21E+05. The flow through a slotted cylindrical probe inserted radially in the pipe also was considered. Spherical slurry particles with diameters from 10 μm to 1000 μm were considered with solid volume fractions of 12%, 24%, and 35%. Computations were performed with ANSYS FLUENT 12 software using the Realizable k-ε turbulence model and the enhanced wall treatment function. Comparisons of computed vertical profiles of solid volume fraction to results in the literature showed good agreement. Symmetric, nearly flat solid volume fraction profiles were observed for 38 μm particles for all three initial solid volume fractions. Asymmetric solid volume fraction profiles with greater values toward the bottom were observed for the larger particles. Changes in the profiles of turbulent kinetic energy also were observed. These changes are important for optical measurements which depend upon the mean concentration profiles as well as the turbulent motion of the slurry particles.

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