Apparent Viscosity Of Suspension Research Articles

Numerical Investigation on Effect of Bubbles Arrangement and Volume Fraction on Apparent Viscosity of Bubbly Suspensions

Background:: Bubbly suspensions can be often run into in natural and industrial processes. The addition of bubbles with different sizes can lead to a significant change in the rheological properties of a matrix liquid. It is extremely significant to fully understand the rheological properties of bubbly suspensions for improving process efficiencies and optimizing productive processes. background: Bubbly suspensions can be often run into in natural and industrial processes. The addition of bubbles of different sizes can greatly change the rheological properties of matrix liquid. It is extremely significant to fully understand the rheological properties of bubbly suspensions for improving process efficiencies and optimizing productive processes. Objective:: The objective of this study is to explore qualitatively the physical law and internal mechanism of the apparent viscosity of suspensions formed by a Newtonian liquid containing different bubbles. Methods:: Based on the parallel plate model of shear flow, the volume of fluid method (VOF) was used to investigate the effect of bubble arrangement and volume fraction on the apparent viscosity of bubbly suspensions at low volume fractions. The piecewise linear interface calculation (PLIC) method was applied to reconstruct the interface based on the phase function. Results:: The present results show that the relative viscosity (ηr) of bubbly suspensions shows a nonlinear change with an increase in bubble volume fraction (ϕ). When the capillary number (Ca) is less than 0.6, ηr shows a nonlinear increase with an increase in ϕ (ηr increases from 1 to 1.03 with an increase in ϕ from 0 to 2.94% at Ca=0.1). However, Ca is greater than or equal to 0.6, ηr shows a nonlinear decrease with an increase in ϕ (ηr decreases from 1 to 0.92 with an increase in ϕ from 0 to 2.94% at Ca=2.5). Even if ϕ is the same, different arrangements of bubbles can lead to different magnitudes of apparent viscosity of bubbly suspensions Conclusion:: As ϕ increases, the region of low shear rate increases, which leads to a non−linear decrease in the relative viscosity. When ϕ is the same, the different arrangements of bubbles can lead to different effects on bubble dynamics and flow fields. This results in different viscous dissipation in bubbly suspensions. Thus, the apparent viscosity of bubbly suspensions is different. other: Nothing

Use of sand pore-size distribution to predict cement suspension groutability

The investigation reported herein aims toward the development of novel, easy-to-use models based on the pore-size distributions of sands for the groutability prediction of cement suspensions in permeation grouting projects for soil improvement. The models were determined using 367 groutability measurements obtained in this research effort by conducting injection tests into 54 sands with different gradations. The documentation of model performance was based on a large database comprising the results of 604 injection tests conducted by other researchers with ordinary and microfine cement suspensions. Suspension groutability is improved by increasing sand characteristic pore size and suspension water/cement ratio and decreasing cement characteristic grain size and suspension apparent viscosity. The proposed models developed using the Binary Logistic Regression method, exhibit coefficients of multiple determination approximately equal or greater than 0.80 and estimate successfully the outcome of the injection tests collected from other studies at rates ranging from 70% to 76%.

Friction characteristics of proppant suspension and pack during slickwater hydraulic fracturing

Proppant transport is a crucial part of the slickwater hydraulic fracturing process, during which numerous hard particles are injected into formations with fracturing fluid to avoid fracture closure and maintain conductivity for hydrocarbon transport. Consequently, the distribution of proppants in fractures determines the well-to-reservoir contact efficiency and long-term post-fracture performance. Proppant distribution is controlled primarily via the transportation of suspended granules and the stability of proppant packs within fractures, whereas suspended granule transport and proppant pack stability can be profoundly affected by the friction characteristics of suspended and packed proppants, respectively. However, inter-particle friction is underestimated in numerical simulations based on the continuum assumption, leading to unrealistic proppant distribution patterns. Moreover, few experimental studies have discussed the friction characteristics of proppant packs. In this study, frictional parameters—such as the apparent viscosity of suspensions, internal friction angle, and cohesion of proppant packs—were measured by means of specially designed experiments. The ranges of the internal friction angle and cohesion ranged from 25.56° to 31.81° and 0.264 kPa–3.839 kPa, respectively, when the viscosity of slickwater was less than 50 mPa s. The correlation between the friction factor, average particle size, and liquid viscosity was determined. Based on the experimental results, new insights into model improvement and more accurate numerical simulations for solid-liquid flow were obtained.

Experimental Studies and Comparative Analyses on Apparent Viscosity of Solid Particle, Droplet, and Bubble Suspensions

Background: Suspensions can be frequently seen in natural, industrial, and agricultural processes. The addition of dispersed phases (such as solid particles, droplets, and bubbles) greatly affects the rheological properties of matrix liquid. Therefore, it is very important to understand the rheological properties of particle suspensions for optimizing production processes and improving process efficiencies. Objective: To explore qualitatively the physical law and internal mechanism of the apparent viscosity of suspensions formed by a Newtonian liquid containing solid particles, droplets, and bubbles, respectively. Methods: The apparent viscosity of suspensions was measured and analyzed using a rotary rheometer (MCR302), and the evolution of particles was recorded using a highspeed camera (Revealer 2F01M). Results: When the deformation of deformable particles (such as bubbles or water droplets) is slight (close to a sphere in shape), or the arrangement of rigid particles is disordered, the relative viscosity of suspensions is greater than 1. When the deformation of deformable particles is large (greatly deviating from a sphere in shape) or rigid particles are arranged in order, the apparent viscosity of suspensions decreases and the relative viscosity of suspensions containing deformable particles is less than 1. Conclusion: The apparent viscosity of suspensions is closely related to particle shape, particle arrangement, and volume fraction. The higher volume fraction of particles significantly influences the apparent viscosity of suspensions.

Influence of solids concentration and solid/polymer interaction on the apparent viscosity of drilling fluids

Drilling fluids perform several functions such as lubrication and cooling of the drill bit, carrying the cuttings to the surface and also maintaining the stability of the well. The physicochemical characteristics of solid particles affect the drilling fluid properties, such as density, chemical composition, and surface charge. In this research, the effects of concentration, surface charge, and adsorption of different solid additives (Barite, Calcite, and Glass spheres) in carboxymethylcellulose (CMC) aqueous solutions were evaluated to quantify its influence on the apparent viscosity of drilling fluids. A study of the polymer hydration time was also carried out. The suspensions were characterized and analyzed by the rheological parameters, the morphology, the surface charge, and the chemical composition. The results showed that suspensions with solids concentration higher than 25% (m/v) presented an increase of the frictional effect of solids, leading to a significant increase in the apparent viscosity of the suspensions. The morphology of the glass spheres facilitated the fluid flow, leading to the lowest apparent viscosity among the suspensions. Ca2+ ions from calcite solids reduced the energy barrier against flocculation, making the apparent viscosity of calcite suspensions the highest. The barite suspensions showed the highest zeta potential value (in modulus) among all suspensions. The appearance of two bands related to the carbonyl in the FTIR spectrum of barite suspensions proves chemical adsorption with the CMC polymer, justifying its lower apparent viscosity compared to calcite suspensions.

PyOIF: Computational tool for modelling of multi-cell flows in complex geometries

A user ready, well documented software package PyOIF contains an implementation of a robust validated computational model for cell flow modelling. The software is capable of simulating processes involving biological cells immersed in a fluid. The examples of such processes are flows in microfluidic channels with numerous applications such as cell sorting, rare cell isolation or flow fractionation. Besides the typical usage of such computational model in the design process of microfluidic devices, PyOIF has been used in the computer-aided discovery involving mechanical properties of cell membranes. With this software, single cell, many cell, as well as dense cell suspensions can be simulated. Many cell simulations include cell-cell interactions and analyse their effect on the cells. PyOIF can be used to test the influence of mechanical properties of the membrane in flows and in membrane-membrane interactions. Dense suspensions may be used to study the effect of cell volume fraction on macroscopic phenomena such as cell-free layer, apparent suspension viscosity or cell degradation. The PyOIF module is based on the official ESPResSo distribution with few modifications and is available under the terms of the GNU General Public Licence. PyOIF is based on Python objects representing the cells and on the C++ computational core for fluid and interaction dynamics. The source code is freely available at GitHub repository, runs natively under Linux and MacOS and can be used in Windows Subsystem for Linux. The communication among PyOIF users and developers is maintained using active mailing lists. This work provides a basic background to the underlying computational models and to the implementation of interactions within this framework. We provide the prospective PyOIF users with a practical example of simulation script with reference to our publicly available User Guide.

Prediction of cement suspension groutability based on sand hydraulic conductivity

The experimental investigation reported herein aims toward the development of groutability prediction models based on the hydraulic conductivity of sand and other parameters affecting the groutability of cement suspensions. For the purposes of the present study, suspensions of three different cement types, each at four different gradations, having water to cement (W/C) ratios of 1, 2 and 3, by weight, were injected into dry and dense sand columns with a height of 36.5 cm. The tested cements cover the range from ordinary to microfine materials having nominal maximum grain sizes of 100, 40, 20 and 10 μm. Six uniform, clean sands with different grain sizes were used alone or mixed in various proportions to obtain 48 additional sands, with different gradations, for grouting. Suspension groutability is improved by increasing cement fineness and suspension W/C ratio or by decreasing apparent viscosity and is controlled by the hydraulic conductivity and the gradation of the sand. The groutability and filtration limits defined in the present study, are based on sand hydraulic conductivity and suspension apparent viscosity and depend on cement fineness and sand gradation. The best model developed by performing Binary Logistic Regression analyses of the injection test results is regarded as an efficient tool for the prediction of groutability of cement suspensions in sands with different gradations, as it exhibits a coefficient of multiple determination equal to 0.914 and estimates successfully the outcome of the injection tests available from this study and collected from other studies at a rate equal to 89% and 70.5%, respectively.

Effects of particle-size distribution and solid additives in the apparent viscosity of drilling fluids

The rheological behavior of drilling fluids depends on the physicochemical characteristics of viscosifying, weighting and bridging agents, such as particle size distribution, charges, chemical composition and density. The accurate controlling of the viscosity profile ensures a higher performance in the drilling process. In this work, the influence of polymers and the particle-size of barite, calcite and glass spheres in the apparent viscosity of suspensions was evaluated. Carboxymethyl cellulose (CMC) and xanthan gum (XG) dissolved in water were used as viscosifying agents. The rheological characteristics of suspensions were evaluated, as well as their zeta potential and microstructure properties. The suspensions of fine material particles presented higher values of shear stress. The CMC polymer increased apparent viscosity at more significant levels than XG and the polymer chain characteristic was predominant over the solid effect. Barite and glass spheres suspensions presented higher zeta potential and lower shear stresses values when compared to calcite suspensions which presented a stronger electrostatic interaction with polymers. Statistical tests were performed using the analysis of variance and results were validated inside 95% of confidence level.

Modeling shear-induced particle ordering and deformation in a dense soft particle suspension

We apply the lattice Boltzmann method and the bead-spring network model of deformable particles (DPs) to study shear-induced particle ordering and deformation and the corresponding rheological behavior for dense DP suspensions confined in a narrow gap under steady external shear. The particle configuration is characterized with small-angle scattering intensity, the real-space 2D local order parameter, and the particle shape factors including deformation, stretching and tilt angles. We investigate how particle ordering and deformation vary with the particle volume fraction ϕ (=0.45–0.65) and the external shear rate characterized with the capillary number Ca (=0.003–0.191). The degree of particle deformation increases mildly with ϕ but significantly with Ca. Under moderate shear rate (Ca = 0.105), the inter-particle structure evolves from string-like ordering to layered hexagonal close packing (HCP) as ϕ increases. A long wavelength particle slithering motion emerges for sufficiently large ϕ. For ϕ = 0.61, the structure maintains layered HCP for Ca = 0.031–0.143 but gradually becomes disordered for larger and smaller Ca. The correlation in particle zigzag movements depends sensitively on ϕ and particle ordering. Layer-by-layer analysis reveals how the non-slippery hard walls affect particle ordering and deformation. The shear-induced reconfiguration of DPs observed in the simulation agrees qualitatively with experimental results of sheared uniform emulsions. The apparent suspension viscosity increases with ϕ but exhibits much weaker dependence compared to hard-sphere suspensions, indicating that particle deformation and unjamming under shear can significantly reduce the viscous stress. Furthermore, the suspension shear-thins, corresponding to increased inter-DP ordering and particle deformation with Ca. This work provides useful insights into the microstructure-rheology relationship of concentrated deformable particle suspensions.

Adsorption of procyanidins onto chitosan-modified porous rice starch

Polyphenolic bioflavonoids are easily oxidized when exposed to oxygen during the processing or storage. This research developed a porous chitosan-modified starch for the adsorption of procyanidins. The modified starch was fabricated by a facile surface modification of chitosan on porous rice starch. Besides the investigation of the morphologies and structures of starches, the adsorption kinetics of procyanidins onto starches was evaluated. The modified starch was mesoporous with a relative moderate specific surface area at 1.13 ± 0.05 m2/g, and the interactions between starch and chitosan were intermolecular hydrogen bonds. The modification of chitosan resulted in the positive zeta potential of starch at pH 2-10. The enzymolysis reduced starch size slightly and induced a decrease in the apparent viscosity of starch suspension, while the modification of chitosan increased starch size and induced an increase in the apparent viscosity of the suspension. The adsorption capacity of the modified starch towards procyanidins was significantly improved and reached 96 ± 3% of the total amount of procyanidins, and the adsorption was chemisorption or strong surface complexation rather than mass transport. The results suggested that the porous chitosan-modified starch might be used as an efficient adsorbent for polyphenols.

Interplay of inertia and deformability on rheological properties of a suspension of capsules

AbstractThe interplay of inertia and deformability has a substantial impact on the transport of soft particles suspended in a fluid. However, to date a thorough understanding of these systems is still missing, and only a limited number of experimental and theoretical studies are available. We combine the finite-element, immersed-boundary and lattice-Boltzmann methods to simulate three-dimensional suspensions of soft particles subjected to planar Poiseuille flow at finite Reynolds numbers. Our findings confirm that the particle deformation and inclination increase when inertia is present. We observe that the Segré–Silberberg effect is suppressed with respect to the particle deformability. Depending on the deformability and strength of inertial effects, inward or outward lateral migration of the particles takes place. In particular, for increasing Reynolds numbers and strongly deformable particles, a hitherto unreported distinct flow focusing effect emerges, which is accompanied by a non-monotonic behaviour of the apparent suspension viscosity and thickness of the particle-free layer close to the channel walls. This effect can be explained by the behaviour of a single particle and the change of the particle collision mechanism when both deformability and inertia effects are relevant.

Tunable fall velocity of a dense ball in oscillatory cross-sheared concentrated suspensions

AbstractThe fall velocity of a dense large ball in a suspension of neutrally buoyant non-Brownian particles subjected to horizontal oscillatory shear is studied. As the strain amplitude is increased, the velocity increases up to a maximum value before decreasing to the value that it would have in a resting suspension. The higher the frequency is, the stronger the effect is. The falling ball velocity can be largely increased in the presence of the oscillatory cross-shear flow. For instance, for a particle volume fraction of$\varPhi =0.47$it reaches four times the value it has in the unsheared suspension. At small strain amplitudes, it turns out that the velocity of the falling ball is determined by a balance between the steady drag flow, which drives the apparent suspension viscosity toward a high value, and the oscillatory cross-shear, which lessens it. A simple model is proposed to explain the experimental observations at small strain amplitude. The velocity decrease observed at larger amplitude is not completely understood yet.

Rheological and Interfacial Property of Nano-Al with HTPB, GAP and PET

Rheological and interfacial property of nanoAl with Hydroxyl-terminated polybutadiene (HTPB), glycidyl azide polymer (GAP) and poly (ethyleneoxide-co-tetrafuran)(PET) were investigated by means of RS-300 rheometer, DCAT21 dynamic contact angle measuring instrument, interface surface tension meter (Germany) and X-ray photoelectron spectroscopy (xps). Rheological properties of three binders and nanoAl/binder suspensions in the mixing ratio of 1:2 were discussed. Results show that Three kinds of binders exhibit pseudoplastic characteristics with the apparent viscosity of less than 3 Pa s,and have weak interaction between molecular chain segment of itself. Within 30~60°C, with temperature increasing, the apparent viscosity of nanoAl suspensions decreases, in which the nanoAl/HTPB and nanoAl/GAP belong to pseudoplastic fluid of sensitive to temperature, with flow activation energy of 38.05 kJ/mol and 52.07 kJ /mol, respectively, but nanoAl/PET belongs to a bingham fluid of sensitive to changes in the shear rate, with flow activation energy of only 1.506 kJ/mol. The contact angles of nanoAl,GAP,HTPB and PET were measured by means of dynamic contact angle/surface tension instrument. The calculated values of adhesion and spread coefficient of nanoAl with binders decrease in the order Wnano-Al/PET>Wnano-Al/GAP>Wnano-Al/HTPB and Snano-Al/PET>Snano-Al/GAP>Snano-Al/HTPB.The results indicate that the interactions of nanoAl with binders decrease in the order nanoAl/PET>nanoAl/GAP>nanoAl/HTPB,which is consistent with the trends of apparent viscosity of the suspensions . Binding energy of Oxygen in nanoAl/HTPB is 532.03 ev,which is bigger than that of nanoAl,and indicate a strong action between nanoAl and HTPB.

Rheological properties of palygorskite–bentonite and sepiolite–bentonite mixed clay suspensions

This study examines the influence of layer charge and smectite content on the rheological properties of mixed bentonite–palygorskite suspensions. Eight bentonite samples containing smectite with layer charge ranging between 0.38 and 0.54e/huc were used to prepare 5% w/v mixed palygorskite–bentonite aqueous suspension at pH7. The influence of smectite on the apparent viscosity and yield point of palygorskite suspensions depends on the proportion of the smectite in the mixture and the layer charge and charge localization of the smectite. The interaction between the two end member clay minerals is maximum at low percentage (10 to 20%) of bentonite in the mixture. Low charge and high charge smectite tended to improve and deteriorate, respectively, the yield point and apparent viscosity of the suspension. This behaviour seemed to be related to the influence of layer charge of smectite on the degree of delamination and the thickness of smectite quasicrystals, which consequently determine the number of particles involved in the interaction and the strength of particle–particle linkages.

Rheology and sedimentation velocity of alkaline suspensions of hematite particles at elevated temperature

This study aims to characterize the sedimentation velocity and the rheology of suspensions of hematite particles suspended in strongly alkaline media at 100 and 110°C, as done for an alternative electrochemical process in development for iron production by direct electrode reduction of hematite. Considering the medium used in the process, i.e. 12% (v/v) suspension of hematite particles in 50% sodium hydroxide aqueous, the sedimentation velocity of hematite particle at 110°C is 0.010mm/s, which is very slow because the average size of the solid particles is around 10μm and the significant collisions and interactions occuring between the particles in the concentrated suspension. Two geometries were used to characterize the rheological behavior of the apparent viscosity of the suspension of 12% (v/v) (i.e. 33wt%) at 100°C: a conventional Couette geometry and a helical ribbon mixer. The suspension was found shear thinning in the range of shear rate studied. The rheological behavior of the suspension can be described by a power-law model. The apparent viscosity of the hematite suspension estimated at a shear rate between 0.5 and 10s−1 is between 100 and 20mPas for the two geometries. The apparent viscosity calculated from the terminal velocity of 10μm particles is of the same order of magnitude of the results obtained with the two rheometer configurations. The effect of the particle concentration on the sedimentation velocity and viscosity of the hematite suspensions was also studied.

The Maximum Solid Loading and Viscosity Estimation of Ultra-Fine ZnO-Al<sub>2</sub>O<sub>3</sub> Mixed Powders Aqueous Suspensions

The rheological behavior of sub-micron zinc oxide and alumina mixture powders aqueous suspension has been investigated over a wide range of volumetric solids loading (Ø = 0.2–0.55), in which polyacrylic acid (PAA) was used as a dispersant. The dependence of relative viscosity (ηr)–solids loading (Ø) determined experimentally was compared with models. The experimental results showed that the suspension apparent viscosity (η) reached a minimum as the dispersant addition reached 0.2 wt%, the viscosity increased with the solids loading and the rheological behavior of the suspension was content basically with the model proposed by Liu. From ηr–Ø relationship the maximum solid loading (Øm) was estimated to be 0.55, which was in accord with our experimental results.

Detection of the II–I Etiracetam solvent-mediated polymorphic transformation through the online monitoring of the suspension apparent viscosity

Although going to complex techniques can be useful at some stage of process development of crystallization processes, the goal of this article is to show that process control can also be achieved with relatively simple measurements, depending of course on what type of control is needed. Focusing on the Etiracetam crystallization process, this work demonstrates the potential of the online monitoring of the power dissipated in the suspension, a property that can be directly related to the suspension apparent viscosity for the detection of the solvent-mediated polymorphic transformation from form II to form I. Even if the work presented in this paper focused on a specific crystallization process, this easy-to-use method seems promising for the control of other crystallization processes exhibiting solvent-mediated polymorphic transformations with similar characteristics: (i) significant difference in the PSD of the crystals of the stable and the metastable forms, (ii) solid volumetric fraction in the suspension higher than 40% and (iii) absence of phenomena (breaking, attrition, agglomeration, secondary nucleation, etc.) interfering with the polymorphic transformation and affecting the PSD of the crystals.

Rheological Behaviour of an Insoluble Lemon Fibre as Affected by Stirring, Temperature, Time and Storage

In this work, the effect the preparation method (two different stirring systems at two temperatures and times), fibre concentration (between 2% and 3%), temperature (between 10 °C and 50 °C) and storage time (between 24 h and 50 days at 5 °C) had on the flow properties of a suspension of dietary lemon fibre prepared with a 45° Brix sucrose solution were evaluated. This information will be helpful in order to discover the best possibilities of using fibre to increase the viscosity of certain kinds of products, depending on the processing, storage and consumption conditions. The obtained results indicate that all the aspects which contribute to increase component solubilisation and the interaction of the insoluble fraction with the aqueous phase when preparing the suspension, such as a decrease in particle size, a rise in temperature or a longer homogenization time, entail a higher apparent viscosity. Moreover, favoring the solubilisation in the preparation process leads to a more stable rheological behaviour of the suspension during storage. As expected, the apparent viscosity of suspensions was dependent on the shear rate, concentration and temperature. A thixotropic behaviour of fibre suspension was only observed at a very low shear rate (5 s−1).

APPARENT VISCOSITY OF FORMULATIONS OF INULIN CHICORY EXTRACT (Cichorium intybus L ) WITH MODIFIED AND HYDROLYZED STARCHES

Rheological properties of chicory root extracts were determined at 25°C, 40°C and 55°C. Samples consisted of pure concentrated extract and concentrated extract formulated with hydrolyzed and modified starch. All suspensions exhibited a pseudoplastic behavior, with an index value (n) varying from 0.42 to 0.97 in the shear rate range of 14 to 264 s -1 . Statistical models indicate that the apparent viscosity of suspensions, formulated with the two different starches, are affected principally by the proportion of hydrolyzed starch, the proportion of modified starch and the fraction of the two starches in the total mixture.

Effect of ionic surfactants on bauxite residues suspensions viscosity

Measurement of the rheological property of bauxite residue sample received from an Australian alumina refinery, treated with a number of cationic and anionic surfactant in laboratory has been carried out using a Brookfield viscometer for the assessment of the effect of surfactants on the residue viscosity. Sodium laurate, prepared with an excess of sodium hydroxide, was found to be effective while direct addition of anionic surfactants (lauric acid and sodium laureth sulphate) and cationic (cetyl trimethyl ammonium bromide) produce only moderate effect on the red mud suspension apparent viscosity at 65 °C. The experimental data appear to confirm the crucial role of the cation sodium in the process of adsorption of anionic surfactants on the flocculated red mud particles.