Suspension Of Particles In Flow Research Articles

Simplified level set discrete element modeling of particle suspension flows in microfluidics: clogging statistics controlled by particle friction and shape

Simplified level set discrete element modeling of particle suspension flows in microfluidics: clogging statistics controlled by particle friction and shape

Influence of Thermal Slip and Ohmic Dissipation Effects on Particulate Suspension Flow through a Channel with Non-Parallel Walls

The main theme of this paper is a numerical investigation of fluid-particle flow in a channel with aslant walls (divergent channel) by taking thermal slip and Ohmic heating into account. The shooting technique with the RK-4 method is exploited to solve the system of dimensionless equations. Graphical discussions of the effects of emerging factors have been conducted for both fluid and particle aspects of temperature and velocity profiles. A perfect match is found when the current results are compared to the previous ones. The results reveal that the fluid phase temperature diminishes but particle phase temperature improves with an augmentation of the thermal slip parameter. These types of flows are used by a variety of industries, including the processing of waste water, mines, petrochemical sectors.

Spatio-temporally resolved dynamical transitions in flow of Pickering emulsions through porous media

Pickering emulsions, when formulated using suitable particles, can exhibit both droplet–droplet and droplet–grain attraction while flowing through porous media. Despite their potential impact on the flow behavior of Pickering emulsions, the underlying mechanisms and dynamics of these attractions are not yet fully understood. To address this, we developed a custom-built micro-sandpack apparatus coupled with confocal microscopy to simultaneously measure the pressure gradient and visualize the flow patterns of emulsions. Our results reveal that the flow of attractive Pickering emulsions displays large-amplitude oscillations in the pressure gradient which cannot be explained using traditional models (e.g. geometric straining, filtration, or continuum). We have identified localized flow patterns characterized by particle attachment and deposition to nearby grains, droplet deposition, jamming of droplets within the throat, and droplet release. These patterns occur cyclically, corresponding to the gradual and rapid changes in the overall pressure gradient. Photonic force microscopy confirmed the strength of droplet–droplet attraction and revealed the underlying cause of this flow dynamics: the formation of chains of nanoparticles that tether droplets together. Our work provides new insights into the mechanism for self-regulated morphological evolution of Pickering emulsion during flow through porous media, resulting from the combined effects of droplet jamming/straining (in line with prior observations of emulsion flow through porous media) and particle deposition (typically observed in the flow of particulate suspensions).

Sub-diffusion flow velocimetry with number fluctuation optical coherence tomography.

We have implemented number fluctuation dynamic light scattering optical coherence tomography (OCT) for measuring extremely slow, sub-diffusion flows of dilute particle suspensions using the second-order autocovariance function. Our method has a lower minimum measurable velocity than conventional correlation-based OCT or phase-resolved Doppler OCT, as the velocity estimation is not affected by the particle diffusion. Similar to non-dilute correlation-based OCT, our technique works for any Doppler angle. With our analysis we can quantitatively determine the concentration of particles under flow. Finally, we demonstrate 2D sub-diffusion flow imaging with a scanning OCT system at high rate by performing number fluctuation correlation analysis on subsequent B-scans.

The movement law and orientation control of rectangular particles in the viscous fluid domain based on IS-FEM

Understanding the movement law and orientation control mechanism of non-spherical particles are significant for industrial applications. In this work, the flow characteristics of rectangular particles, in the uniform and wedge viscous fluid domain, are simulated by the immersed smoothed finite element method (IS-FEM). The influences of mesh resolution and time-step on particle velocity are analyzed, and the numerical procedure is validated by the published model and sedimentation experiments. The operating parameters that affect the particle flow are systematically studied, including Reynolds number, initial angle, channel offset distance, and aspect ratio. Moreover, the particle angles are adjusted by the velocity gradient of fluid domains. The result indicates that the velocities, angle, and drag of rectangular particles are closely related to the working conditions. The long axis of rectangular particles is consistent with the flow direction in shrinking fluid domains and is perpendicular to the flow direction in expanding fluid domains. The angle distribution law of rectangular particles in moving wedge fluid domains is determined. These findings provide a theoretical foundation for particle sedimentation and suspension flow, which is helpful for the further separation and orientation control of mixed particles.

Capturing of particles in suspension flow through a micro cross-shaped channel

Capturing of microscale particles through microfluidics has been a flourishing research area in chemical and biological engineering applications. This work follows our previous report (Zhang et al., AIChE J., vol. 66, 2019, e16822) by using micro plane laser-induced fluorescence (μPLIF) and high-speed photography technology to study the flow of a diluted suspension of buoyant particles in a micro cross-shaped channel at 30≤Re≤350. Particular attention is paid to particle accumulation behaviors caused by vortex breakdown within the steady engulfment flow and vortex shedding flow. Three particle capture modes are identified in accumulation regions including the particle chain mode, the steady and unsteady particle cluster mode at 100≤Re≤300. Multiple stable equilibrium orbits formed by captured particles in accumulation regions are attributed to the axial force balance. In addition, perturbations in particle trajectories induced by the vortex shedding flow or particle-particle interactions contribute to the particle release.

Influence of the solid fraction on the clogging by bridging of suspensions in constricted channels.

Clogging can occur whenever a suspension of particles flows through a confined system. The formation of clogs is often correlated to a reduction in the cross-section of the channel. In this study, we consider the clogging by bridging, i.e., through the formation of a stable arch of particles at a constriction that hinders the transport of particles downstream of the clog. To characterize the role of the volume fraction of the suspension on the clogging dynamics, we study the flow of particulate suspensions through 3D-printed millifluidic devices. We systematically characterize the bridging of non-Brownian particles in a quasi-bidimensional system in which we directly visualize and track the particles as they flow and form arches at a constriction. We report the conditions for clogging by bridging when varying the constriction width to particle diameter ratio for different concentrations of the particles in suspension. We then discuss our results using a stochastic model to rationalize the influence of solid fraction on the probability of clogging. Understanding the mechanisms and conditions of clog formation is an important step for optimizing engineering design and developing more reliable dispensing systems.

Particle Behaviours in Free Surface Flow of Particle Suspensions

In this study, the suspension flows in a Hele-Shaw cell were experimentally examined. We focused on the free surface of suspension in a Hele-Shaw radial flow and discussed the effect of particle behaviors on the change in surface shape. The test fluids used were two kinds of suspension with a different particle size. The volumetric fraction of each fluid was 40 vol.%. In the observation of free surface in the Hele-Shaw flow, it was found that concave and convex parts appeared on the free surface with a time. Furthermore, at the inside region of surface undulation, the occurrence of the particle-induced viscous fingering was confirmed. Measuring velocity profiles inside the viscous fingering using the particle imaging velocimeter (PIV), we found that the velocity in the fingering region became higher than those of entire suspension. The difference between the particle velocity inside fingering and that of entire suspension suggested that the shear flow in the Hele-Shaw cell affected the particle behaviors. Furthermore, since the temporal changes in the fingering shape was different between both fluids, the particle behaviors inside the viscous fingering might relate to the particle migration in the perpendicular direction to flow direction due to the local change in the shear deformation.

Modulation of elasto-inertial transitions in Taylor–Couette flow by small particles

Particle suspensions in non-Newtonian liquid matrices are frequently encountered in nature and industrial applications. We here study the Taylor–Couette flow (TCF) of semidilute spherical particle suspensions (volume fraction $\leq 0.1$ ) in viscoelastic, constant-viscosity liquids (Boger fluids). We describe the influence of particle load on various flow transitions encountered in TCF of such fluids, and on the nature of these transitions. Particle addition is found to delay the onset of first- and second-order transitions, thus stabilising laminar flows. It also renders them hysteretic, suggesting an effect on the nature of bifurcations. The transition to elasto-inertial turbulence (EIT) is shown to be delayed by the presence of particles, and the features of EIT altered, with preserved spatio-temporal large scales. These results imply that particle loading and viscoelasticity, which are known to destabilise the flow when considered separately, can on the other hand compete with one another and ultimately stabilise the flow when considered together.

Numerical and linear regression analysis on MHD two‐phase flow in an asymmetric nonuniform channel

AbstractThe flow through asymmetric nonuniform (convergent) channels with the effect of the magnetic field have a pronounced impact in engineering and biological fields such as chemical and food industries, blood flow through capillaries, and arteries, and so forth. With this motivation, the present study focuses on convective hydromagnetic particulate suspension flow in an asymmetric convergent channel under the heat generation effect. The numerical method is applied to solve the nondimensionalized equations governing the transport process of fluid and particle flow and its heat. To check the convergence of the computational results, a grid independence test has been performed. A comparison test has been made to validate the results and an admirable agreement is noticed with published results. Computation results are reported for the influence of emerging parameters on the fluid as well as particle velocity and temperature profiles through graphs and tables. A method of slope linear regression through data points is presented to study the impact of various parameters on skin friction and Nusselt number. The study pioneers the investigation on the significance of the combined influence of cross‐flow Reynolds number and magnetic field on fluid and particle in the convergent channel and also reports its importance on drag coefficient and rate of heat transfer at the walls. It is perceived that a reduction in fluid velocity takes place with an increment in Magnetic parameter, Grashof number, and Reynolds number. An augmentation in fluid temperature is noted with an increment in Prandtl number and heat source parameter.

Analysis of MHD pulsatile flow of Jeffrey fluid in a diseased inclined tapered porous artery exposed to an inclined magnetic field

In this analysis, a theoretical model is proposed to examine the collective effect of slip velocity, magnetic field, and inclination angles on an unsteady non-Newtonian particulate suspension flow in an inclined diseased tapered tube with a porous medium by applying an external inclined magnetic field. By deploying integral transform methods, analytical expressions are obtained for the flow characteristics such as velocity profiles of fluid and particles, wall shear stress, flow rate, and flow resistance. With the aid of numerical computations, the significance of inclination angle, porous medium, and magnetic intensity are analyzed and illustrated graphically. Further, various physiological parameters affecting the flow characteristics are discussed which would facilitate the rheological functions of blood in the field of biology, biomedicine, and engineering sciences.

Physical modeling of the dam-break flow of sedimenting suspensions

This paper develops a physical model able to describe the dam-break flow of particulate suspensions that sediment progressively during propagation at a constant velocity that solely depends on the mixture properties. The model considers the suspension as an equivalent fluid of constant density and negligible viscosity and leads to a good prediction of the flow duration and deposits shape. These findings allow the formulation of consistent shallow-water equations that can be used to compute the dense basal layer of small-volume pyroclastic flows.

A constitutive model for sheared dense suspensions of rough particles

In a concentrated suspension, particles come into contact due to the presence of asperities on their surfaces. As a result, the contact forces and interparticle friction become one of the important factors governing the rheology of rigid particle suspensions at high concentrations. We show that a load-dependent friction model can be used to reproduce the experimentally observed shear thickening [ST—continuous and discontinuous (DST)] behavior with an increase in the asperity size. Increasing the particle surface roughness size leads to a decrease in the critical shear rate above which shear-thickening takes place, a reduction in the critical volume fraction for DST and an increase in the viscosity jump across non-shear-thickened to shear-thickened regime. In this paper, we propose a constitutive model to quantify the effect of increasing the roughness size on the rheology of dense ST suspensions as well as on the critical shear rate for ST and the critical volume fraction for DST. We fit this model to our simulation data for stress controlled shear flow of dense rough particle suspensions. Once the fitting is complete, these equations are used to predict exact volume fractions and shear stress values for transitions between three regimes on the shear stress-shear rate flow state diagram for different roughness values. The results of this study can be used to tune the particle surface roughness for manipulating the dense suspension rheology according to different applications.

Effect of geometrical confinement on the flow of soft microgel particle pastes

In this paper, we determine the effect of confinement on the shear flow of concentrated soft microgel particle suspensions. Utilizing a flexure-based microgap rheometer (FMR), aqueous suspensions of swollen P(NIPAM-co-AA) microgel particles of 4μ m diameter at different volume fractions larger than 64 vol% are subjected to shearing deformations between plates separated by gaps of 5–120μ m while monitoring the stress response at different rates. Describing the stress evolution from a balance of elastohydrodynamic lubrication and elastic forces following the approach of Cloitre and Bonnecaze, it could be shown that already below a critical confinement level on the order of 10 particle diameters an increase of the interparticle pressure leads to a rising shear stress at a given rate in the yielded regime. This effect is strongest for particle volume fractions close to the critical closest packing, with two orders of magnitude increase in flow resistance when approaching the single-particle confinement level, whereas this confinement effect on the flow decreases when raising the concentration. Furthermore, it could be shown that, at the onset of the yielding of the suspensions, the confinement is increasing the effective modulus, but not the yield strain.

Increase of turbulent drag by polymers in particle suspensions

Viscoelastic turbulent flows of particle suspensions are studied using direct numerical simulations. In the presence of a moderate concentration of particles, the beneficial effect of polymers in terms of drag reduction are lost, and an increase in drag is observed for sufficiently dense suspensions.

Numerical simulations of oscillatory shear flow of particle suspensions at finite inertia

We perform immersed-boundary-method numerical simulations of oscillatory shear flow of suspensions of mono-disperse non-colloidal rigid spherical particles in a Newtonian liquid from the dilute to ...

Effects of slip conditions and compressibility on the peristaltic flow of particulate suspension in a planar channel

This paper concerns with the peristaltic flow of a particle–fluid suspension (as blood model) through asymmetric two-dimensional channel with slip conditions. The problem formulation is presented for a duct filled with a compressible viscous fluid mixed with rigid spherical particles. The resulting problems are solved by the perturbation expansion method. The effects of different physical parameters such as particles concentration, compressibility parameter, and slip parameter have a significant effect on velocity distributions and are presented and discussed graphically. It is found that the mean axial velocity increases as the slip parameter increases at a minimal compressibility parameter, and it decreases at a higher value of compressibility parameter with increasing slip parameter. This paper gives a scope for estimating the effects of the slip conditions of two-phase flow characteristics with compressible fluid problems and helps in understanding the role of the engineering applications of pumping solid–fluid mixture by peristaltically driven motion.

Thermal Radiation Effects on Casson Dusty Boundary-Layer Fluid Flow Along an Isothermal Truncated Vertical Cone

A boundary-layer analysis is presented to study the effect of intense thermal radiations on natural convection flow of Casson dusty particulate suspension past a truncated cone. Contribution of radiative heat flux in a two-phase model is reported by means of Rosseland diffusion approximation. In order to convert the governing equations into non-dimensional form, a continuous set of transformations is used and the resulting equations are integrated numerically via an implicit finite difference method. Numerical results for Casson dusty fluid flow characteristics are shown graphically under the variation of various important parameters. It is found that thermal radiation parameter, $$R_\mathrm{d}$$, and dusty fluid parameter, $$\alpha _\mathrm{d}$$, increase the magnitude of heat transfer rate. Casson rheological parameter, $$\beta $$, has also pronounced effect on the flow and it increases the rate of heat transfer and reduces wall skin friction coefficient.

A numerical study with experimental validation of liquid-assisted fluidization of particle suspensions in a HydroFloat cell

Fluidization can assist in coarse particle flotation. Here the dynamic behaviors of three-dimensional flows of particle suspensions (without air bubbles) in the counter-gravity regime in a HydroFloat cell with a circular cross-section are numerically studied by using the Eulerian-Eulerian approach with the RNG k−ε turbulence model. The kinetic theory of granular flow is adapted to analyze the particle behaviors. Simulation results are validated by using a laboratory-scale HydroFloat cell. The effect of superficial liquid velocities on the fluidized beds of spherical and non-spherical particles is investigated. The predicted results are within 4% of experimental results of bed expansion. The pressure drop and bed expansion of non-spherical particles are higher than those of spherical particles. Distributions of time-averaged particle axial velocity, particle volume fraction, particle kinetic energy, liquid turbulent kinetic energy, and dispersion rate are examined. The simulation results show that the particle kinetic energy is high near the column wall and low in the central region. The energy flows and the efficiency of energy transfer from the liquid phase to the solid phase in the fluidized bed cell are calculated and examined. Finally, the obtained data are analyzed to develop a correlation for the overall particle volume fraction, which would be useful for further studies of three-phase bubble-particle fluidization in flotation.

Three-Dimensional Boundary layer Flow and Heat Transfer of a Fluid Particle Suspension over a Stretching Sheet Embedded in a Porous Medium

Abstract This article presents the effect of nonlinear thermal radiation on three dimensional flow and heat transfer of fluid particle suspension over a stretching sheet. The combined effects of non-uniform source/sink and convective boundary condition are taken into consideration. The governing partial differential equations are transformed into ordinary differential equations using similarity variables, which are then solved numerically by using Runge Kutta Fehlberg-45 method with shooting technique. The influence of various parameters on velocity and temperature profiles are illustrated graphically, and discussed in detail. The results indicate that the fluid phase velocity is greater than that of the particle phase for various existing parameters.