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An alternative model is proposed for hydrodynamic stability of plane parallel flow of an incompressible Newtonian fluid with suspended solid particles. For heavy particle-laden dusty gases with negligible particle volume fraction, the effective complex-form mean velocity in the modified Orr-Sommerfeld equation derived by the present model is showed to be essentially identical to the well-known Saffman's classical results. In the limit cases of small or large Stokes number of particles, simple formulas are derived for the effective Reynolds number ratio of the particle-laden suspension to the clear fluid without particles under otherwise identical conditions. The derived formula for particles of finite particle-to-fluid density ratio and small Stokes number is verified by comparing predicted results with known data, although a comparison of the derived formula with known results for particles of finite density ratio and large Stokes number cannot be made here due to the lack of available data. It is hoped that the present work could offer a conceptually novel and relatively simplified model for hydrodynamics of solid particle-fluid suspensions. [ABSTRACT FROM AUTHOR]

Particle suspension and deposition dynamics are significant factors affecting the level of mixing quality in solid-liquid two-phase stirring processes. In general, the ability to increase the suspension rate and minimize deposition effects is instrumental in improving the uniformity of particle mixing, accelerating the reaction of involved solid-liquid two-phase, and improving the efficiency of production operations. In this work, suspension and deposition indicator based on the Betti number and a uniformity indicator are introduced and obtained by means of image analysis. The influence of the blade type, rotation speed, blade diameter and blade bottom height on the particle suspension/deposition characteristics and mixing uniformity are carefully investigated. The experimental results show that the two-phase motion region can be divided into three local regions, including a bottom motion along the wall, a low-degree suspension region under the blade and a high suspension region above the blade. The best degree of particle suspension is attained by the double-inclined blade paddle at a speed of 270 r/min, a paddle diameter ratio of 0.414, and a height-diameter ratio of 0.086. The double-inclined blade paddle has a better effect on promoting particle suspension and solid-liquid two-phase mixing uniformity. [ABSTRACT FROM AUTHOR]

This study evaluated the suspension stability of passion fruit nectar formulated with different concentrations of carboxymethyl cellulose (CMC). Passion fruit nectars with 0, 0.02, 0.1 and 0.2% (w/v) CMC were placed at rest in test tubes at room temperature (~25 °C) to measure the phase separation height for 87 h. Passion fruit nectars with 0 and 0.02% (w/v) CMC showed notable phase separation, while those with 0.1 and 0.2% (w/v) CMC were relatively stable suspensions. The analysis of sedimentation kinetics revealed that passion fruit nectars with 0 and 0.02% (w/v) CMC presented respectively: maximum sedimentation velocity of 0.426 m/s and 0.260 m/s, equilibrium sedimentation index of 46.494% and 20.434%, and sedimentation rate speed of 0.0362 and 0.0556%/s. A concentration of 0.2% (w/v) CMC is recommended in passion fruit nectar to maintain the appearance of a stable suspension, which is a characteristic desired by the consumer.

The bubbling flow plays a key role in gas–liquid–solid fluidized beds. To understand the intrinsic fluidization behaviors at the discrete bubble and particle scale, coupled simulations with the volume of fluid model and the discrete element method are performed to investigate the effects of the gas inlet velocity, particle properties and two-orifice bubbling flow on particle fluidization. Three-dimensional simulations are carried out to accurately capture the dynamic changes in the bubble shape and trajectory. A bubbling flow with a closely packed bed is simulated to study the onset of particle fluidization. The obvious phenomena of particle fluidization are presented by both the experiment and simulation. Although an increasing gas inlet velocity promotes particle fluidization, the good fluidization of particles cannot be achieved solely by increasing the gas inlet velocity. When the channel is packed with more particles, the bubbles take a longer time to pass through the higher particle bed, and the bubbles grow larger in the bed. The increase in particle density also extends the time needed for the bubbles to escape from the bed, and it is more difficult to fluidize the particles with a larger density. Even if more particles are added into the channel, the percentage of suspended particles is not significantly changed. The percentage of suspended particles is not increased with a decrease in the particle diameter. The particle suspension is not significantly improved by the bubbling flow with two orifices, while the particle velocity is increased due to the more frequent bubble–particle collisions. The findings from this study will be beneficial in guiding the enhancement of particle fluidization in multiphase reactors. [ABSTRACT FROM AUTHOR]

The main objective of the present article is to investigate the hydromagnetic particle Reiner-Rivlin fluid flow in an asymmetric (divergent) channel. The non-dimensionalized equations solved by the shooting method. The graphs are intended to examine how different developing parameters affect the thermal and velocity fields. The effects of various parameters on skin friction and the rate of heat transmission along channel walls are investigated using tabular data. The current results are in admirable agreement with the published data. The fluid velocity delineates in the first portion of the channel and rockets up in the second when the inelastic parameter increases. An increase in cross-flow Reynolds number is accompanied by an increasing tendency in particle temperature. Several areas, like metal steam resistors, fiber suspension in paper manufacture, etc., are significantly impacted by the magnetic field's action on Reiner-Rivlin fluid through asymmetric channels. [ABSTRACT FROM AUTHOR]

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Particle suspension is considered powerful and perspective in enhancing heat transfer, but the unclear nature of particle‐loaded flow limits further understanding of particle suspension. Therefore, in this paper, orthogonal experiments and the arbitrary Lagrangian‐Eulerian method were used to investigate the heat transfer characteristics of particle‐loaded flow. Results indicate that when the particle is at the inlet of the microchannel, the factors arranged in important order are the Reynolds number, blockage ratio, particle initial position, specific heat capacity, and thermal conductivity. When the particle is far from the microchannel inlet, the factors arranged in important order are the Reynolds number, blockage ratio, particle initial position, thermal conductivity, and specific heat capacity. [ABSTRACT FROM AUTHOR]

Biomechanics is a field for mechanical study of the structure and function of living organisms, which finds many applications in various fields such as engineering, medicine and biology. Research in blood, systems showed that the blood volume is effectively changed by the strength and direction of shear stress on the vessel wall, also inducing changes in the vessel diameter. Most studies about wall shear stress in bends or branches are based on macroscopic single-phase flow, and more studies should be necessary to investigate wall shear stress distribution by multi-phase flow considering blood as a suspension. In this study, we focused on the flow characteristics of particle suspension, and aimed to analyze a flow field with asymmetrical differences in the shear stress on each wall of a two-dimensional (2D) parallel plates flow, i.e., a flow field with an asymmetric velocity profile. A 2D curvilinear channel was used to reproduce this flow field, and the regularized lattice Boltzmann method and the virtual flux method were used as the computational methods. Our results confirmed that the equilibrium positions were either two asymmetric points or a single point, depending on the radius of curvature of the channel and Reynolds number. The radial pressure gradient was found to be a major factor for the presence of a single equilibrium position. Furthermore, when the radius of curvature was decreased, the equilibrium position shifted closer to the inner wall side, and the relative viscosity of the suspension became higher because of the decreasing the distance between the particle and the inner wall.

Suspensions of monodisperse spherical particles under shear flow were simulated using a solid-liquid two-phase model based on coupled lattice Boltzmann method (LBM) and discrete element method (DEM). Evaluating the shear stresses due to the viscous behavior of the bulk fluid, the hydrodynamic interaction between particles and fluid, and the physical contact between particles, the contribution of each factor to the suspension viscosity was investigated. The results showed that in the range of low to moderate particle volume fractions, the viscosity of suspensions is mainly determined by the action of the fluid, and that the contribution of particle contact increases with increasing particle volume fraction. In particular, the flow behavior of dense suspensions should be viewed not as a fluid motion but as the motion of a group of particles. From these results, in order to predict and control the rheological properties of particle suspensions, it is important to understand that the main factors increasing viscosity vary with the concentration range of interest. [ABSTRACT FROM AUTHOR]

The goal of the current investigation is to examine the impact of magnetic field and heat source effects on a Reiner–Rivlin particulate flow through an asymmetric channel (convergent channel). The transformed governing equations are solved by employing the shooting technique with the RK4 method. To check the convergence of the computational results, a grid independence test has been performed. The impact of influential parameters on fluid as well as particle phases of velocity and temperature fields have been analyzed graphically. The present results exactly match previously published results in some limited cases. As the Reynolds number and magnetic parameter increase, the fluid phase velocity increases on the left side and decreases on the right part of the channel. Different fields, including metal steam resistors, paper production, and fibre suspension, are significantly impacted by the magnetic field’s effect on Reiner–Rivlin fluid through asymmetric channels. [ABSTRACT FROM AUTHOR]

Predictions of clarified layer depth and solids suspension in a draft tube reactor were investigated at a moderate solids loading of 16% v/v using both a RANS approach (k − ε) and a scale-resolving approach using Stress Blended Eddy Simulation (SBES). The multiphase flow was modelled using an Algebraic Slip model and the impact of drag law, turbulent particle diffusion and number of particle size classes was examined. The inclusion or exclusion of turbulent particle diffusion is found to dominate the RANS results, with resulting poor prediction of clarified layer depth and solids suspension under some conditions. In contrast, the SBES model is found to give good agreement with experimental data and the results show there is no need for a modelled turbulent dispersion force in this system if the large-scale turbulence structures responsible for particle transport are explicitly resolved. [Display omitted] • Clarified layer depth and solids suspension in a draft tube reactor studied. • RANS and Stress Blended Eddy Simulation (SBES) predictions compared. • Impact of modelled turbulent dispersion force investigated. • SBES predictions superior to RANS and in close agreement with experimental data. [ABSTRACT FROM AUTHOR]

[Display omitted] The vacuum method is a widely adopted technique for eliminating bubbles from polymers containing particles. To investigate the influence of bubbles on the behavior of particles and the concentration distribution in high-viscosity liquids under negative pressure, experimental and numerical methods have been employed. The experimental findings demonstrated a positive correlation between the diameter and rising velocity of bubbles and the negative pressure. As the negative pressure increased from − 10 kPa to − 50 kPa, the position of the region where the particles were concentrated in the vertical direction was elevated. Furthermore, when the negative pressure exceeded − 50 kPa, the particle distribution became sparse and layered locally. The Lattice Boltzmann method (LBM) integrated with the discrete phase model (DPM) was utilized to investigate the phenomenon, and the outcomes revealed that rising bubbles have an inhibitory effect on particle sedimentation, and the extent of inhibition was determined by the negative pressure. In addition, vortexes generated by differences in the rising velocity between bubbles resulted in a particle distribution that was sparse and layered locally. This research provides a reference for achieving desired particle distributions using a vacuum defoaming approach and should be further studied to extend its applicability to suspensions containing particles with different viscosities. [ABSTRACT FROM AUTHOR]

The shear rheology of particle suspensions in shear-thinning polymeric fluids is studied experimentally using parallel plate measurements and numerically using fully resolved, 3D finite volume simulations with the Giesekus fluid model. We show in our experiments that the steady shear viscosity and first normal stress difference coefficient of the suspension evolve from shear-thickening to substantially shear-thinning as the degree of shear-thinning of the suspending fluid increases. Moreover, in highly shear-thinning fluids, the suspension exhibits greater shear-thinning of the viscosity than the suspending fluid itself. Our dilute body-fitted simulations show that in the absence of hydrodynamic interactions, shear-thinning can arise from the particle-induced fluid stress (PIFS), which ceases to grow with increasing shear rate at low values of β (solvent viscosity ratio) and finite values of α (the Giesekus drag coefficient). In a Giesekus suspending fluid, the polymers surrounding the suspended particle are unable to stretch sufficiently at high Weissenberg numbers (Wi) and the reduced polymer stress results in a lower PIFS. When coupled with the shear-thinning stresslet, this effect creates an overall shear-thinning of the viscosity. We then explore the effects of particle-particle interactions on the suspension rheology using immersed boundary simulations. We show that multiparticle simulations are necessary to obtain the shear-thinning behavior of the per-particle viscosity of suspensions in shear-thinning fluids at moderate values of β. Particle-particle interactions lead to a substantial decrease in the PIFS and an enhancement of the shear-thinning of the stresslet compared to the single particle simulations. This combination leads to the shear-thinning of the per-particle viscosity seen in experiments. We also find that very low values of β and finite values of α have opposing effects on the per-particle viscosity that can lead to a nonmonotonic per-particle viscosity versus shear rate in a highly shear-thinning fluid. Overall, the addition of rigid particles to highly shear-thinning fluids, such as joint synovial fluid, leads to increased viscosity and also increased shear-thinning at high shear rates. [ABSTRACT FROM AUTHOR]

We study the effect of varying polymer concentration, measured by the dimensionless polymer viscosity partition function β , on the steady shear rheology of rigid particle suspensions using direct numerical simulation of the Oldroyd-B model. We compare the bulk rheology using immersed boundary simulations at Φ = 2.5 % and 5 % to body-fitted single-particle simulations and find that the per-particle viscosity and first normal stress difference coefficient are always shear-thickening at all values of β considered. However, as β decreases, the polymer stress transforms the flow field near each particle from closed concentric streamlines to helical streamlines that advect stretched polymers away from the particle surface. At low β , the polymer stress is diffuse, where the distribution of the particle induced fluid stress (PIFS) caused by the stretched polymers is spread out in the simulation domain rather than concentrated near the particle surface. Therefore in multiparticle simulations, the polymer stress can be significantly affected by particle-particle interactions. The stress generated by a given particle is disrupted by the presence of particles in its vicinity, leading to a significantly lower PIFS than that of the single-particle simulation. In addition, at increased volume fractions and low values of β , the polymer stress distribution on the particle surface shifts so as to increase the magnitude of the polymer stress moments, resulting in a shear-thickening stresslet contribution to the viscosity that is not seen in single particle or high β simulations. This result indicates that for suspensions in highly viscoelastic suspending fluids that are characterized by a low β parameter, hydrodynamic interactions are significant even at modest particle concentrations and fully resolved multiparticle simulations are necessary to understand the rheological behavior. [ABSTRACT FROM AUTHOR]

In the chemical and water treatment industries, it is necessary to achieve maximum contact between the solid and liquid phase, thus promoting the mass and heat transfer, to obtain a homogeneous solution. Increasing stirring speed is the most recommended solution in different types of reactors: stirred tank, column, and tubular. However, this inadvertently increases the energy consumption of the industry. Determination of the minimum speed, labeled the just suspended speed (Njs) and crucial to attaining homogeneity, has been widely investigated. Numerous studies have been carried out to assess formulas for determining the solid particle speed in various reactor types. Given the limitations of the existing formulations based on a generalization of a unique equation for computing Njs for all soil classifications, it appears that most formulas can only approximate complex phenomena that depend on several parameters. A novel formula was developed, and the results given in this paper demonstrate the effectiveness of generating significant uncertainties for the estimation of Njs. The purpose of this study was the elaboration of experiment-based data-driven formulas to calculate Njs for different particle size classes. Nonlinear multiple regression (MNLR) models were used to generate the new formulas. The gradient descent optimization algorithm was employed to solve the hyperparameters of each novel equation, utilizing supervised learning. A comparison of the data indicated that the unique formulas presented in this study outperformed empirical formulas and provide a useful means for lowering energy consumption, while increasing the heat and mass transfer in torus type reactors. [ABSTRACT FROM AUTHOR]

Heat transfer characteristics of random suspensions of 0.25 aspect ratio (AR) cylinders are investigated for Reynolds numbers (Re) between 10 and 300 and solid fraction (φ) ranging from 0.1 to 0.3 using particle resolved simulations. The effect of particle inclination with respect to flow and particle clustering on heat transfer is investigated. The Nusselt number decreases with an increase in inclination angle and the dependence becomes stronger as φ and Re increase. On the other hand, while prolate ellipsoid suspensions of AR 2.5 follow the same trend, the Nusselt number increases with inclination angle as AR increases to 5 and 10 and as φ increases. Local particle clustering nominally decreases the Nusselt number because of the dominance of thermal wakes. At low φ⁠, this effect is felt only at low Re⁠, but as φ increases, the effect spreads to higher Re⁠. Similar but weaker trends are also found in suspensions of prolate ellipsoids of AR 2.5, 5, and 10. High AR, low Re prolate ellipsoids exhibit the greatest dependence of Nusselt number on local solid fraction. Implementation of two independent definitions of reference length, i.e., volume equivalent sphere diameter deq for ellipsoids and diameter dp of the cylindrical particle in the correlation of Tavassoli et al. (2015, "Direct Numerical Simulation of Fluid-Particle Heat Transfer in Fixed Random Arrays of Non-Spherical Particles," Chem. Eng. Sci., 129, pp. 42-48) provides good estimates of the respective suspension mean Nusselt numbers. [ABSTRACT FROM AUTHOR]

A coupled method of discrete element method (DEM) and volume of fluid (VOF) is applied to study the particle suspension in top‐sealed solid–liquid tanks with a free‐surface. VOF is used to track the gas–liquid free‐surface, and DEM is used to calculate the movement and interaction of particles. As the air between the cover and free‐surface in a sealed tank is very limited, the free‐surface evolution process that a big vortex is generated quickly and then shrinks to a smaller one in sealed stirred tanks is reported first in this paper. In addition, the effects of pitched blade turbine (PBT) with different blade pitched angles (including 30°, 45°, 60°, 75°, and 90°) on solid suspension, free‐surface, and power number are investigated. Finally, the relationships between particle motion and fluid flow during the stirring are studied carefully. Fluid flow plays a dominant role during the start‐up of the stirring; and then, due to the contact of particles, some particles could obtain the larger velocity than the fluid. The results obtained here are helpful to design the sealed stirred tanks with PBT. [ABSTRACT FROM AUTHOR]

In the chemical and water treatment industries, it is necessary to achieve maximum contact between the solid and liquid phase, thus promoting the mass and heat transfer, to obtain a homogeneous solution. Increasing stirring speed is the most recommended solution in different types of reactors: stirred tank, column, and tubular. However, this inadvertently increases the energy consumption of the industry. Determination of the minimum speed, labeled the just suspended speed (Njs) and crucial to attaining homogeneity, has been widely investigated. Numerous studies have been carried out to assess formulas for determining the solid particle speed in various reactor types. Given the limitations of the existing formulations based on a generalization of a unique equation for computing Njs for all soil classifications, it appears that most formulas can only approximate complex phenomena that depend on several parameters. A novel formula was developed, and the results given in this paper demonstrate the effectiveness of generating significant uncertainties for the estimation of Njs. The purpose of this study was the elaboration of experiment-based data-driven formulas to calculate Njs for different particle size classes. Nonlinear multiple regression (MNLR) models were used to generate the new formulas. The gradient descent optimization algorithm was employed to solve the hyperparameters of each novel equation, utilizing supervised learning. A comparison of the data indicated that the unique formulas presented in this study outperformed empirical formulas and provide a useful means for lowering energy consumption, while increasing the heat and mass transfer in torus type reactors.

In this study, we performed direct simulations of particle suspensions in a simple shear flow with a viscoplastic model (Bingham fluid) using a finite-element/fictitious-domain method, as a model system for cuttings transport with a drilling mud in the oil and gas exploration. Bulk rheology and particle interaction were investigated via several example problems including single-particle, two-interacting particle, and many-particle problems for various solid fractions in both Bingham and Newtonian fluids. We report that, at low shear rate, huge reductions occur in both the relative bulk viscosity and angular velocity of particle suspension in a Bingham fluid compared to that in a Newtonian fluid. This indicates that, although particle incorporation increases bulk viscosity in a Bingham fluid, the amount of increase appears much smaller than that with the Newtonian medium, and particle motions were restricted to some extend at a low shear rate with a yield stress fluid. Moreover, the suppression in viscosity increase with particles disappears at a high shear rate, just like Newtonian particle suspension. This phenomenon has been interpreted by the suppressed particle angular rotation in a Bingham fluid. In addition, flow fields with low shear regions, where the viscosity of a Bingham fluid is high and the fluid mobility decreased significantly, on the left and right sides of a particle also confirm this interpretation. The two-interacting particle problem reveals delayed particle interaction with increased time period in particle trajectories (drafting, kissing, tumbling and separation) in a Bingham fluid. Similar behaviors with the suppression in viscosity increase can be also observed in the many-particle problem. [ABSTRACT FROM AUTHOR]

High solids content complicates in situ analysis of chemical processing, biological suspensions, and environmental streams. In most cases, analytical methods require at least one pre‐treatment step of a small volume of sample before a particle‐free fluid can be analyzed. We have developed a continuous in situ sampler that can "sip" particle‐free solution from a turbulent high solids content stream (a slurry). An open microfluidic chip with an extended slit opening shields the internal laminar flow from the turbulence outside. Unlike other open chips, our chip does not require close proximity to a solid surface and operates in turbulent environments for hours without maintenance. Two applications are demonstrated: monitoring FeIII in a stirred slurry of mixed ore particles at high solids loading (4 %wt) and paracetamol tablet dissolution profiles for two different formulations. [ABSTRACT FROM AUTHOR]

Mixing in stirred tanks is vital to a wide range of industrial processes, typically requiring solids to be fully suspended and evenly distributed. The quality of suspension and mixing is typically measured visually. Such measurements are thus subject to human interpretation and can only feasibly be conducted in transparent systems – an uncommon condition in industrial systems. Visual measurements of homogeneity must also infer full 3D distributions of particles solely from the observation of a limited section thereof. This work details methods by which a system's homogeneity and state of suspension may be measured and quantified with no human interpretation, which can extract information from opaque systems and consider full 3D data acquired throughout the interior of a given system. [ABSTRACT FROM AUTHOR]

The particle suspension velocity has a strong practical impact on pneumatic conveying systems. The barycenter and centroid of large nonspherical particles are not in the same point, and the particles rotate under the action of torque when the particles are subjected to an unbalanced force in the flow field. This rotation causes the vortexes or turbulence near the particles. The stirring effect of large particle is especially obvious and directly affects the particle suspension behavior. To investigate the suspension behavior of large (5–30 mm) nonspherical particles in vertical pneumatic conveying, the CFD-DEM coupling method is adopted to realize the coupling between the solid phase and the gas phase and establish the coupling simulation model between the nonspherical particles and flow field. The suspension velocity relations of three flow drag zones are calculated on the basis of the particle-size method and the relationships between the pipe diameter, particle shape, Reynolds number and fluid drag coefficient. It will help in designing and operation of pneumatic conveying systems. The dynamic characteristics of large nonspherical particles in the vertical flow field are analyzed according to the particle suspension experiment and simulation results. The experiment and simulation results show that the nonspherical particles rotate in the vertical flow field, which can reduce the required flow velocity of large nonspherical particles in vertical pneumatic conveying. Unlabelled Image • The relations between particle diameter and suspension velocity are obtained. • The particle irregular shape causes the rotational motion in experiment. • The pressure gradient of flow field causes the particle rotation in simulation. • The flow drag of flow field changes with particle windward area. • Rotational motion reduces flow velocity required for vertical pneumatic conveying. [ABSTRACT FROM AUTHOR]

Suspending particles in liquids is an important and versatile case for industrial stirring processes. By using advanced optical, non‐invasive measurement techniques like particle image velocimetry (PIV), it is possible to gain deep insights into the involved fluid dynamics without affecting the flow. However, for suspensions, the application of PIV is not trivial since both, suspended and tracer particles are present and need to be discerned during experiments. The here presented method development solves this problem and thus leads to a better insight into turbulent kinetic energy distribution, which can be utilized for process optimization through improved stirred vessel design. [ABSTRACT FROM AUTHOR]

The effect of wall slip conditions, porous media, and heat transfer on peristaltic inflow of MHD Newtonian fluid with suspended particles in a catheterized tube has been studied with long-wavelength and low-Reynolds number approximations. The analytical solution has been derived for velocity and temperature. The amplitude ratio, particle concentration, catheter size, and the dimensionless flow rate were used to discuss the pressure gradient. The solutions for velocity and temperature derived in the analysis have been computed numerically and investigated. The tube surface is maintained at a fixed temperature. The variations of physical variables with the pertinent parameters were discussed graphically. The mathematical model presented corresponds to the flow in the annular space between two concentric tubes. It has been deduced that the thermal energy is reduced with particles' concentration and with slip condition through the catheterized tube. The flow accelerates with the magnetic field and slip condition at the wall, whereas it decreases at the catheter. The catheter size has a different effect on both pressure drop and friction force. [ABSTRACT FROM AUTHOR]

Suspensions of an elliptical particle in Poiseuille flow are investigated by using the multiple-relaxation-time lattice Boltzmann method coupled with the Galilean-invariant momentum exchange method. The elliptical particle shows lateral migration and final equilibrium, which are similar to the classical Segré–Silberberg effect. Because the elliptical shape interacts with the parabolic velocity distribution of the Poiseuille flow, the particulate behaviors remarkably contain regular wave accompanied by nonuniform rotation. When the blockage ratio grows up, the equilibrium position of the particle moves towards the channel centerline and the rotation period becomes long. With the increase of the aspect ratio, the rotation period becomes short; the equilibrium position shows a shape of saddle and reaches its bottom at nearby aspect ratio 0.5. Surprisingly, the numerical results show that the equilibrium position is insensitive to Reynolds number (Re) of Poiseuille flows in the range 3 ≤ R e ≤ 300. This work can make active promotions to the researches of blood circulation of birds, whose red blood cell is oval or elliptical in shape. [ABSTRACT FROM AUTHOR]

When agitating mesenchymal stem cells adhered on microcarriers in bioreactors, a compromise has to be found between sufficient particle suspension and limitation of hydromechanical stresses. The present study proposes a strategy to improve the design of an 'elephant ear' impeller at the just‐suspended state by varying its relative size, blade slope angle, and position in the reactor. To do that, computational fluid dynamics simulations were coupled with multi‐objective optimization to minimize the hydromechanical stress encountered by the microcarriers. Two minimization criteria were considered: (P/V)@p and the energy dissipation function EDC. On the basis of 31 conditions, an optimal impeller geometry is proposed. [ABSTRACT FROM AUTHOR]

Highlights • We study particle migration in the flow of apparent yield-stress fluids. • A new regularized viscosity function for viscoplastic behavior is presented. • The regularization leads to a particle-free plug flow at steady-state conditions. • Apparent yield-stress materials enhance the particle flux towards the tube wall. Abstract Suspensions of particles with viscoplastic characteristics are often found both in nature and industrial applications. However, in contrast with the case of suspensions in Newtonian fluids, the dynamics of shear-induced particle migration in yield-stress suspending materials is not yet fully understood. In this work, we present a numerical study of particle migration in pressure-driven, tube flows of suspensions of non-colloidal, spherical particles dispersed in apparent yield-stress fluids. The suspension viscosity is modeled using the classical Krieger–Dougherty equation with a novel regularized viscosity function for viscoplastic materials as the suspending medium viscosity, and the dynamics of shear-induced particle migration is described with the Diffusive Flux Model. The resulting fully coupled, non-linear, one-dimensional model is solved with a second-order finite difference scheme coupled with Newton's method. We present a parametric study that elucidates the role played by the suspension bulk concentration, Plastic number, and power-law index on the velocity profile and particle concentration distribution in the flow. Remarkably, the results show that particle migration in apparent yield-stress fluids leads to a strikingly different pattern of velocity and particle distribution profiles relative to the case of suspensions in Newtonian liquids and true yield-stress materials. [ABSTRACT FROM AUTHOR]

The impact of heat transfer on the magnetohydrodynamic peristaltically induced motion in a channel through porous medium has been investigated. The continuity, momentum, and energy equations have been utilized to represent the flow in a closed form. These non-linear governing equations are solved analytically by employing the perturbation method. The obtained expressions for streamlines, temperature, and heat transfer coefficient are presented through graphs for two dimensions with a small wave number. The variations of physical variables with the pertinent parameters have been presented and discussed. It has been found that the inclusion of fluid suspension brought about a decrease in the temperature distribution. The effect of magnetic field on the temperature of fluid has also been seen to depend upon the position and time. [ABSTRACT FROM AUTHOR]

The paper presents the simulation of a catalyst-paraffin oil slurry hydrodynamics under high pressure and temperature in a convex bottom reactor with a Rushton turbine which was conducted with an application of computational fluid dynamics (CFD) modeling. An analysis to obtain a uniform distribution of solid catalyst particles suspended in paraffin oil was carried out as a potential for biomass liquefaction. The effects of the particle diameter, bed density, liquid viscosity, and the initial solid loading on slurry hydrodynamics in high pressure and temperature behavior were investigated using the Eulerian–Eulerian two-fluid model and the standard k-ε turbulence model. The main objective was to assess the performance in agitating highly concentrated slurries to obtain slurry velocity, concentration, the degree of homogeneity, and to examine their effect on the mixing quality. The results of the analysis are applied to predicting the impact of the most efficient conditions on slurry suspension qualities as potential for biomass liquefaction.

Drug targeting promises to substantially enhance future therapies, for example through the focussing of chemotherapeutic drugs at the site of a tumor, thus reducing the exposure of healthy tissue to unwanted damage. Promising work on the steering of medication in the human body employs magnetic fields acting on nanoparticles made of paramagnetic materials. We develop a computational tool to aid in the optimization of the physical parameters of these particles and the magnetic configuration, estimating the fraction of particles reaching a given target site in a large patient-specific vascular system for different physiological states (heart rate, cardiac output, etc.). We demonstrate the excellent computational performance of our model by its application to the simulation of paramagnetic-nanoparticle-laden flows in a circle of Willis geometry obtained from an MRI scan. The results suggest a strong dependence of the particle density at the target site on the strength of the magnetic forcing and the velocity of the background fluid flow.

Abstract Radioactive liquid waste is often stored in a large capacity (150 m 3 ) horizontal cylindrical tanks. It is necessary to keep the contents of the tank agitated to prevent the settling of fine solids in the tank. In extreme cases, solids settled at the tank base may invoke the system malfunction. This paper deals with the Computational Fluid Dynamic (CFD) modeling of the agitation mechanism considering the turbulent dispersion effects. The simulations are conducted on a standard tank geometry to arrive the optimum jet velocity required to suspend the settled solid particles thoroughly. The distribution of volume phase fraction, velocity magnitude, turbulence kinetic energy (TKE) and eddy dissipation of each phase for different inlet jet velocities (v = 10–25 m / s) have been presented. The spatial variation of these quantities are measured at three different planes in the vessel mainly in the vicinity of the nozzle exit. The results indicate that the jet velocity is a significant parameter that influences the particle suspension. Parametric studies have also been carried out for four different particle sizes, viz. d p = 5, 10, 50 and 100 μ m. The present study revealed that, for the range of parameters covered, the smallest ( d p = 5 μ m) and the largest ( d p = 100 μ m) particle sizes has least effect in terms of solids suspension. Highlights • Jet agitation for solid particle suspension is numerically studied. • The influence of jet velocity and particle size on the flow characteristics is investigated. • This analysis revealed a counter rotating vortex pair originated from the nozzle tip. • Optimal jet parameters are obtained by performing systematic numerical simulations. [ABSTRACT FROM AUTHOR]

The paper studies the particle retention and permeability impairment in porous media. This problem results from the re-injection of produced groundwater during oil production into the oilfields in order to reduce environmental damage. The lattice Boltzmann method (LBM) is used to simulate the fluid flow. The discrete element method (DEM) is adopted to simulate the particle motion. The fluid-solid interactions are simulated using the immersed moving boundary method (IMB). Based on the coupling LBM-DEM-IMB method, the paper studies the effect of particle diameter, flow rate, particle volume fraction and injection amount on the particle retention and permeability impairment. Results indicate that larger particle diameter, lower flow rate, higher volume fraction and more particle injection lead to more severe permeability impairment. In order to further study the effect of particle suspensions on heterogeneous reservoirs, a two-channel model with different permeabilities is established. The simulations show that smaller particles tend to retain in the low permeable channel and its permeability impairment is more severe. On the contrary, larger particles can reduce the permeability of high permeable channel, but they can protect the permeability of low permeable channel due to the mechanism of membrane filtration. Therefore, the sweep efficiency and oil recovery of the heterogeneous reservoirs can be improved by re-injecting produced groundwater after reasonable pretreatment. The re-injection also reduces environmental damage resulting from the large amounts of produced water in petroleum engineering. This paper provides some references for general studies on the flow of particle suspension in porous media. [ABSTRACT FROM AUTHOR]

Rate capability is a critical metric for assessing lithium-ion battery materials, especially in the electric vehicle industry which requires high battery power density. The typical method for rate capability evaluation of battery materials involves electrode processing, battery assembly, and testing on a battery cycler with varying current rates. This method is very important in evaluating battery materials, however, it is time-consuming and depending on the cell type can take days to weeks. Rate capability can also be affected by other factors besides the active material properties including electrode slurry homogeneity, contact junctions formed during battery assembly, and the connectivity of the interfaces within the battery electrodes. Herein, we will describe the use of a technique termed dispersed particle resistance (DPR) to evaluate the battery cathode active material LiCoO 2 (LCO), the first layered oxide evaluated using this method. This new technique works relatively fast, providing qualitative analysis within several minutes, and does not require electrode fabrication or additional materials in the system besides a carrier fluid for the electrolyte. While DPR does not explicitly give rate capability of the materials, DPR was successfully demonstrated to provide the relative rate capability for multiple different LCO samples, as supported by the results obtained from conventional rate capability testing using cycling data. Additionally, the physical properties of the material probed by the DPR were investigated by determining the lithium diffusivity in the crystal structure of the different LCO materials with galvanostatic intermittent titration technique. [ABSTRACT FROM AUTHOR]

The key to achieve an economically more attractive concentrated solar power plant is to work at higher operating temperatures, allowing both higher power conversion efficiencies resulting in a smaller heliostat field for a given energy output, and higher temperature ranges in the storage tanks, with increased energy storage density and smaller size, hence less expensive. This fostered the development of using particle suspensions as heat transfer media. This paper presents a theoretical framework for the energy analysis of a particle-in-tube solar power plant, hybridized, with topping air-Brayton cycle turbine, and bottoming steam block. From studying the effects of essential design parameters on the energy efficiency, the heat transfer efficiency of the turbine air preheater is of paramount importance to increase the solar contribution within the hybrid concept, while the energy efficiency moreover increases by an optimum air-Brayton cycle turbine operation (mostly through the pressure ratio, less by the operating temperature). The overall efficiency of the concept varies from about 40% when using combined low and high pressure Brayton cycle turbines only, to over 48% in a fully combined air-steam concept. Energy efficiency findings are in agreement with the literature data. [ABSTRACT FROM AUTHOR]

Drug targeting promises to substantially enhance future therapies, for example through the focussing of chemotherapeutic drugs at the site of a tumor, thus reducing the exposure of healthy tissue to unwanted damage. Promising work on the steering of medication in the human body employs magnetic fields acting on nanoparticles made of paramagnetic materials. We develop a computational tool to aid in the optimization of the physical parameters of these particles and the magnetic configuration, estimating the fraction of particles reaching a given target site in a large patient-specific vascular system for different physiological states (heart rate, cardiac output, etc.). We demonstrate the excellent computational performance of our model by its application to the simulation of paramagnetic-nanoparticle-laden flows in a circle of Willis geometry obtained from an MRI scan. The results suggest a strong dependence of the particle density at the target site on the strength of the magnetic forcing and the velocity of the background fluid flow. [ABSTRACT FROM AUTHOR]

In particle-laden flows through porous media, porosity and permeability are significantly affected by the deposition and erosion of particles. Experiments show that the permeability evolution of a porous medium with respect to a particle suspension is not smooth, but rather exhibits significant jumps followed by longer periods of continuous permeability decrease. Their origin seems to be related to internal flow path reorganization by avalanches of deposited material due to erosion inside the porous medium. We apply neutron tomography to resolve the spatiotemporal evolution of the pore space during clogging and unclogging to prove the hypothesis of flow path reorganization behind the permeability jumps. This mechanistic understanding of clogging phenomena is relevant for a number of applications from oil production to filters or suffosion as the mechanisms behind sinkhole formation. [ABSTRACT FROM AUTHOR]

We present in this article a novel distributed Lagrange multiplier/fictitious domain (DLM/FD) method for simulating fluid-particle interaction in three-dimensional (3D) Stokes flow. The methodology is validated by comparing the numerical results for a neutrally buoyant particle, of either spherical or prolate shape, with the associated Jeffrey's solutions for a simple shear flow. The results concerning two balls, interacting under creeping flow conditions in a bounded shear flow, are consistent with those available in the literature. We will discuss also the interactions of two balls in a bounded shear flow, when these balls are very close initially. For a prolate ellipsoid rotating in a shear flow under the sole effect of the particle inertia, shear plane tumbling is stable, while log-rolling is unstable. For two prolate ellipsoids interacting in a bounded shear flow, the results are similar to those for two balls if the major axes are initially orthogonal to the shear plane (a result not at all surprising considering that the intersections of the ellipsoids with the shear pane are circular). [ABSTRACT FROM AUTHOR]

[Display omitted] • A scheme was proposed to realize the harmless motion and accumulation of particles. • The particle suspension was effectively suppression, improving product quality and production efficiency. • The research can provide a basis of field productions concerning control technologies of particles. Particle suspension in a turbulent flow can seriously affect the performance of manufactured products in many industrial processes in which the motion of particles cannot be modeled using the numerical method because of the enormous number of particles. Therefore, in this study, a full-scale computational fluid dynamics (CFD) simulation and a 1/5 scaled-down water model experiment were employed to investigate the flow pattern and dynamic behavior of particles in a continuously stirred vessel system. Based on the understanding of the suspension mechanism of settling particles, a particle-suppression device was designed to realize the harmless movement and deposition of particles. The results showed that the flow guidance and division mechanisms of the particle-suppression device led to the inhibition of particle suspensions. In addition, the optimal parameter combination for the device from the water model experiment combined with the orthogonal experimental design, resulted in a 98.3% reduction in the concentration of suspended particles. The suspension of particles was effectively suppressed, which improves product quality and production efficiency. Reliable results can be achieved by combining CFD simulations and water model experiments. [ABSTRACT FROM AUTHOR]

A mathematical model is presented for the steady, two-dimensional magneto-convection heat transfer of a two-phase, electrically-conducting, particle-suspension in a channel containing a non-Darcian porous medium intercalated between two parallel plates, in the presence of a transverse magnetic field. The channel walls are assumed to be isothermal but at different temperatures. The governing equations for the one-dimensional steady flow are formulated following Marble (1970) and extended to include the influence of Darcian porous drag, Forcheimmer quadratic drag, buoyancy effects, Lorentz body force (hydromagnetic retardation force) and particle-phase viscous stresses. Special boundary conditions for the particle-phase wall conditions are implemented. The governing coupled, non-linear differential equations are reduced from an (x,y) coordinate system to a one-dimensional (y) coordinate system. A series of transformations is then employed to non-dimensionalize the model in terms of a single independent variable, , yielding a quartet of coupled ordinary differential equations which are solved numerically using the finite element method, under appropriate transformed boundary conditions. The influence of for example Grashof free convection number (Gr), Hartmann hydromagnetic number (Ha), inverse Stokes number (Skm), Darcy number (Da), Forcheimmer number (Fs),particle loading parameter (PL), buoyancy parameter (B) on the fluid-phase velocity and particle-phase velocity are presented graphically. A number of special cases of the transformed model are also studied. The mathematical model finds applications in solar collector devices, electronic fabrication, jet nozzle flows, industrial materials processing transport phenomena, MHD energy generator systems etc.

Battery active materials are evaluated using numerous material characterization techniques for fundamental understanding, comparative analysis during research and development, and for quality control during manufacturing. Electrochemical properties of the active materials also need to be investigated and validated, and this analysis is very time and material intensive generally requiring electrode fabrication, cell assembly and cell cycling. In addition, evaluating active materials electrochemically in battery cells can be complicated by the electrode microstructure and the contributions of other components within the cell that are not the active materials. In this report, an active material characterization method is demonstrated to provide electrochemical insights for lithium-ion cathode materials by dispersing them into aqueous electrolyte and flowing through an electrochemical reaction cell. This method requires very little active material and time to conduct the measurements, typically requiring under 0.1 grams of material and less than 10 minutes. The measured resistance from this technique provides insights into the electrochemical performance of the active material and generally correlates to the rate capability. This measured resistance is insensitive to other electrode components or electrode microstructure because there is no electrode fabrication step. LiFePO 4 was chosen as a commercial material for initial demonstration of the technique. [ABSTRACT FROM AUTHOR]

Slot coating is a common method in the manufacturing of a wide variety of functional films. In many applications, the coating liquid is a particle suspension and the performance of the final product is directly related to the micro structure of the film. Fundamental understanding of the suspension flow enables a better control of the particle distribution on the coated layer and, consequently, on the coating process and product performance optimization. A common simplified approach to study coating flow of non-colloidal particle suspension is to consider that the particles are uniformly distributed in the coating bead and that the liquid viscosity is constant and equal to the value of the bulk concentration. However, experimental evidences have shown that shear-induced migration leads to non-uniform particle distribution. The literature presents numerical predictions on surface inactive, neutrally buoyant particle suspension flow which have shown that particle distribution in the coated layer strongly depends on the process conditions. Here, we extend the previous analyses to explore the effect of different process conditions, including the effect of particle sedimentation and Marangoni stresses caused by surface-active particles. Results show how particle distribution changes with flow conditions and particle properties, and that Marangoni stresses can change the recirculation pattern of the flow. [ABSTRACT FROM AUTHOR]