Solid Spherical Particles Research Articles

Maximum dust-to-gas mass flux ratio in spherically expanding dusty-gas flow

In this paper, we consider the motion of a solid spherical particle in a spherically expanding gas flow as an elementary model of the gas-dust atmosphere of a comet. Based on the results of numerical simulations we propose an approximation for the terminal dust velocity and an estimate of the maximum dust-to-gas mass flux ratio (in a dusty-gas flow with the dust size distribution given by a power law) which is consistent with assumption of negligible impact of dust on the gas flow (frequently used in simulations of dusty gas flows).

Migration of a slip-spin solid spherical particle in a micropolar fluid-filled circular cylindrical tube

A combined study analytically and numerically for the axially symmetric creeping flow due to a slip-spin solid sphere surface moving in a microstructure fluid of micropolar type along the centreline of a circular cylindrical tube is introduced. This investigation was presented under low Reynolds number conditions. A general solution is obtained by superposing the essential solutions in both spherical and cylindrical coordinates to solve the Eringen micropolar field equations. The condition of the microrotation, along with couple stress, is used at the surface of the solid particle; while the microrotation is used at the inner cylindrical surface. Boundary conditions are imposed initially on the inner cylindrical surface using Fourier transforms and subsequently on the outer surface of the solid particle using a collocation technique. This paper aims to study the wall interaction problem of a translating slip-spin solid spherical particle in a micropolar fluid along the centreline of a circular cylindrical tube. The study also investigates the effect of the addition of slip conditions for velocity and microrotation on the surface of a solid particle. There is good convergence in the numerical findings obtained for the normalised hydrodynamic drag force (the tube-corrected factor) applying on the surface of the solid particle for several values of the micropolarity coefficient, slip-spin coefficients, and the ratio between the radius of the solid particle and tube. Regarding the flow of a solid spherical particle along the centreline of a cylindrical tube, our drag findings compare favourably to the solutions found in the literature. We found that the normalised drag force acting on the solid particle monotonically increases with the increase of the particle-to-tube radius ratio and reaches infinity in the limitless, with the increase of the micropolarity coefficient, and with the increase of the slip-spin coefficients for a steady ratio of particle-to-tube radius.

A Review on Solid Lipid Nanoparticles as Nano Drug Delivery Transporters

Abstract: Solid lipid nanoparticles (SLN) have several potential uses in research for medicine such as drug discovery and drug delivery, an area at the forefront of evolving area of nanobiotechnology. In general, SLNs were created to address the drawbacks of conventional colloidal carriers, including emulsions, liposomes, and polymeric nanoparticles since they provide various advantages such as favourable release profiles and tailored drug delivery with outstanding physical-chemical stability. Solid lipid nanoparticles are spherical solid lipid particles that are distributed in water or an aqueous surfactant solution and are in the nanometer size range. Therefore, SLN is used to deliver hydrophilic and lipophilic drugs. The review article focuses on various aspects of SLN including the structure, the influence of excipients, the drug incorporation model, the principle of release, the method of preparation, characterization, the route of administration and biodistribution, and the application of SLN.

Numerical investigation of particle behavior and erosion wear in a centrifugal pump using coarse-grained Discrete Element Method

Erosion wear presents a significant challenge in the operation of hydrodynamic systems, particularly in centrifugal pumps. To address this issue, this study employs the coarse-grained Discrete Element Method (CGDEM) coupled with Computational Fluid Dynamics (CFD) to predict erosion wear areas and elucidate particle behavior dynamics. The simulation considers spherical solid particles (brown corundum) with diameters ranging from 0.3 mm to 1 mm and volume fractions of 15% and 5%. The flow field is calculated using the Navier-Stokes equations and the shear-stress-transport (SST) k-ω model. Particle movement is tracked using Newton’s second law, considering drag and gravitational forces. Results indicate that the highest turbulent kinetic energy (TKE) occurs at a flow rate of Q = 15 m3/h. Moreover, the pressure reduces slightly when the flow rate increases, although flow velocity might increase with volumetric discharge. Additionally, increased particle diameter leads to greater erosion wear, particularly on blade leading edges, the volute tongue area, and the volute casing belly region. As particle mass concentration intensifies, wear rates on the volute wall and inner hub edge also increase. The study’s robustness is demonstrated through alignment between experimental and numerical data. This investigation offers valuable insights into erosion dynamics in centrifugal pumps, crucial for enhancing operational efficiency and mitigating erosion-induced challenges in these critical systems.

Coupling a torque rheometer with an ultrasonic velocity profiler for evaluating multiphase fluids in oscillatory shear flows

We propose a torque rheometer coupled with an ultrasonic velocity profiler (UVP) for evaluating multiphase fluids as bulk rheology in oscillatory shear flows. The rheometer mainly consists of wide-gap coaxial cylinders, where the outer cylinder is sinusoidally oscillated and the inner cylinder is fixed to a torque sensor for measuring the wall shear stress. Based on Cauchy’s equation of motion, the spatiotemporal distribution of the shear stress is obtained from the velocity information and the wall shear stress as a boundary condition. This rheometer was applied to a carboxymethyl cellulose aqueous solution and compared with a standard torque-type rheometer. The results of the evaluated viscoelastic properties agreed well with each other, indicating the validity of the proposed rheometry. To further investigate the applicability of the rheometer to multiphase fluids, suspensions of solid spherical particles with a diameter of 220μm with volume fraction of 0.8–3.4% were measured, which are out of the applicable ranges of the standard rheometer. For volume fractions up to 3% where the UVP measurement is available, the relative viscosity agrees well with a theoretical formula. This indicates the applicability of the method to examine multiphase fluids.

Investigation of thermal damage in explosive bridgewire detonators via discrete element method simulations

AbstractExploding bridgewire (EBW) detonators are used to rapidly and reliably initiate energetic reactions by exploding a bridgewire via Joule heating. While the mechanisms of EBW detonators have been studied extensively in nominal conditions, comparatively few studies have addressed thermally damaged detonator operability. We present a mesoscale simulation study of thermal damage in a representative EBW detonator, using discrete element method (DEM) simulations that explicitly account for individual particles in the pressed explosive powder. We use a simplified model of melting, where solid spherical particles undergo uniform shrinking, and fluid dynamics are ignored. The subsequent settling of particles results in the formation of a gap between the solid powder and the bridgewire, which we study under different conditions. In particular, particle cohesion has a significant effect on gap formation and settling behavior, where sufficiently high cohesion leads to coalescence of particles into a free‐standing pellet. This behavior is qualitatively compared to experimental visualization data, and simulations are shown to capture several key changes in pellet shape. We derive a minimum and maximum limit on gap formation during melting using simple geometric arguments. In the absence of cohesion, results agree with the maximum gap size. With increasing cohesion, the gap size decreases, eventually saturating at the minimum limit. We present results for different combinations of interparticle cohesion and detonator orientations with respect to gravity, demonstrating the complex behavior of these systems and the potential for DEM simulations to capture a range of scenarios.

Numerical study of particle dispersion in the wake of a static and rotating cylinder at Re = 140 000

In this study, the particle-laden flow in the wake of a static and a rotating cylinder at Reynolds number of 140 000 was investigated using the Reynolds Averaged Navier–Stokes numerical approach. Three turbulence models such as k–ω shear stress transport, Reynolds stress model, and local-correlation transition model (LCTM) were selected to predict the flow topology. Lagrangian approach with one-way coupling was used to track solid spherical particles of different sizes (0.01, 0.1, 2.5, 10, and 50 μm). The study reveals that LCTM is the most accurate to predict the flow topology in both cases. Cylinder's rotation generates different effects on flow structure. It breaks the wake's symmetry and reduces its width, and increases the frequency of vortex shedding and the size of the recirculation zone. Particle transport analysis has revealed that particles' response to the flow depends on their Stokes number and wake flow topology. Particles of 0.01, 0.1, and 2.5 μm distribute in and around vortex cores, while particles of 10 and 50 μm do not penetrate vortex cores. Instead, 10 μm particles accumulate mainly around the periphery of vortices, while 50 μm particles skip the vortex street to the thin shear flow region between vortices to be transported by the mainstream flow. Finally, cylinder rotation reduces the particle spread in the vertical direction and shifts all particle distributions in the cylinder's rotation direction. Analysis of particle dispersion functions showed that cylinder's rotation reduces differences in dispersion extent depending on particle size.

Reversible Binding Interfaces Made of Microstructured Polymer Brushes.

The polymer brush architecture of the end-tethered polymer molecules is one of the most widely used efficient methods to regulate interfacial interactions in colloidal systems found in live matter and manufactured materials. Emerging applications of polymer brush structures require solutions to new tasks in the control of interfacial interactions. The rapid development of live cell manufacturing relies on scalable and efficient cell harvesting methods. Stimuli-responsive surfaces made of surface-grafted poly(N-isopropylacrylamide) (PNIPAM) can bind and detach the adherent cell upon changes in temperature and have been used for cell growth and harvesting. The applications are limited by the requirement to satisfy a range of PNIPAM coating characteristics that depend on the dimensions of the integrin complex in the cell membrane and the basal surface. The analysis of the microstructured surfaces, when adhesive and disjoining functions of the microdomains are decoupled, shows that many limitations of PNIPAM one-component coatings can be avoided by using a much broader range of structural characteristics of the microstructured interfaces composed of alternating disjoining PNIPAM domains and adhesive polymeric domains with cell-affinity functional groups. Temperature-controlled reversible adhesion to such microstructured interfaces is studied here experimentally with model systems of solid spherical particles and by employing simulations for solid and soft membranes interacting with the microstructured surfaces to mimic interactions with soft and solid disk-like particles.

Confinement Effects in Droplet Formation on a Solid Particle.

Formation of a droplet around a spherical solid particle in supersaturated vapor is considered. The number and stability of equilibrium solutions in a closed small system are studied in the canonical ensemble in comparison to an open system in the grand canonical ensemble. Depending on the system's parameters, two modes exist in the canonical ensemble: the first one with only one solution and the second one with three solutions; the presence of the third solution is due to confinement. The analysis is conducted first on a macroscopic thermodynamic level of description, and then the results are supported by studies within two versions of classical density functional theory: the square-gradient approximation with the Carnahan-Starling equation of state for hard spheres on a completely wettable particle and the random-phase approximation with the fundamental measure theory on a poorly wettable particle. In the latter case, a solution breaking the spherical symmetry is observed at a small total number of molecules.

Anisotropic Mean Flow Enhancement and Anomalous Transport of Finite-Size Spherical Particles in Turbulent Flows.

We investigate the influence of dispersed solid spherical particles on the largest scales of the turbulent Arnold-Beltrami-Childress (ABC) flow. The ABC flow is an ideal instance of a complex flow: it does not have solid boundaries, but possesses an inhomogeneous and three-dimensional mean shear. By tuning the parameters of the suspension, we show that particles modulate the largest scales of the flow toward an anisotropic, quasi-two-dimensional and more energetic state. In this regime, particles move along quasistraight trajectories and exhibit anomalous transport.

Deprotonation-assisted electrochemical synthesis of copper nitrotriazole with excellent ignition performance

Electrochemical synthesis serves as a green and efficient method with great application potential. However, it has not been extensively applied in the synthesis of energetic materials. Nitrogen-rich heterocyclic compounds, as a new generation of energetic materials, enjoy advantages such as eco-friendliness, high energy output, and excellent safety performance. This study reports the electrochemical cathodic synthesis of copper nitrotriazole [Cu(NTz)2] using copper chloride and 3-nitro-1,2,4-triazole as a reaction substrate and triethylamine as a deprotonation agent. The obtained Cu(NTz)2 comprises uniform spherical particles of nano lamellae. As the dosage of triethylamine increased from 50 μL to 150 μL, Cu(NTz)2 gradually grew into compact solid spherical particles, significantly increasing the energy output. Notably, the heat release increased from 711 J g−1 to 1301 J g−1, accompanied by a significant positive elevation of ignition performance and peak combustion pressure in the process of confined combustion. This greatly boosted the energetic performance of Cu(NTz)2. Moreover, Cu(NTz)2 demonstrates insensitivity to electrostatic discharge (E50＞225 mJ) and friction (FS＞360 N), suggesting excellent safety performance. Owing to its outstanding energetic and safety performance, Cu(NTz)2 boasts great potential for application as pyrotechnic compositions, including military gas-producing and incendiary agents. Moreover, it has been corroborated that Cu(NTz)2 can be applied as a micro ignitor.

Axisymmetric motion of a solid particle embedded in a Brinkman micropolar fluid in the presence of a plane wall

The axisymmetric motion of a solid spherical particle embedded in a hydrogel medium in the presence of a planar wall surface is investigated semi-analytically. The hydrogel medium is modeled as a porous medium saturated with a microstructure fluid of micropolar type. The no-slip velocity and no-slip spin boundary conditions are considered at both the particle surface and the plane wall surface. The sixth-order differential equation describing the stream function of the micropolar fluid flow through the voids of the porous medium is constructed under the assumption of low Reynolds numbers. The general solution of the equation satisfied by the stream function in the porous region is obtained from the superposition of basic solutions in both cylindrical and spherical coordinates. To satisfy first the boundary condition at the planar surface, we apply the Fourier–Bessel transforms and then at the surface of the particle by a boundary collocation technique. The collocation scheme for the normalized drag force acting on the particle is calculated with good convergence for various values of the relevant parameter. Our results are in good agreement with the available data in the literature. The findings of the present investigation demonstrate that the presence of the planar surface, micropolarity, and permeability parameters has significant effects on the drag force. This study is motivated by its potential application on micro- and ultra-filtration.

Unraveling the motion and deformation characteristics of red blood cells in a deterministic lateral displacement device

Deterministic Lateral Displacement (DLD) device has gained widespread recognition and trusted for filtering blood cells. However, there remains a crucial need to explore the complex interplay between deformable cells and flow within the DLD device to improve its design. This paper presents an approach utilizing a mesoscopic cell-level numerical model based on dissipative particle dynamics to effectively capture this complex phenomenon. To establish the model’s credibility, a series of numerical simulations were conducted and the numerical results were validated with nominal experimental data from the literature. These include single cell stretching experiment, comparisons of the morphological characteristics of cells in DLD, and comparison the specific row-shift fraction of DLD required to initiate the zigzag mode. Additionally, we investigate the effect of cell rigidity, which serves as an indicator of cell health, on average flow velocity, trajectory, and asphericity. Moreover, we extend the existing theory of predicting zigzag mode for solid spherical particles to encompass the behavior of red blood cells. To achieve this, we introduce a new concept of effective diameter and demonstrate its applicability in providing highly accurate predictions across a wide range of conditions.

Penetration of a solid spherical particle into artificial and natural wet granular ice layers: Dynamic strength characterization

The strength of wet granular ice layers is an important quantity for modelling the behaviour of ice accretions encountered in aircraft engine icing since it determines the dynamics of the collision of ice crystals, their penetration into the layer, breakup and the characteristics of the ejected material. In the present study, impact tests of 3.18 mm nylon spheres are conducted on wet granular ice layers for a dynamic strength characterization. An experimental setup and methodology are designed to measure the crater depth for impact velocities ranging from 5 ms−1 to 90 ms−1. Experiments are conducted using both ice layers generated by ice crystal accretion on a solid substrate inside an icing wind tunnel and artificial ice layers prepared in a laboratory environment. By fitting the Poncelet penetration equation to the experimental data, two dimensionless parameters are derived that characterize the strength of the investigated ice layers in relation to the layer inertial resistance and apparent yield strength. A key finding is that strong connections between individual ice particles exist for ice layer generated in the wind tunnel, originating from re-freezing of liquid water near the particle contacts. Only by re-enforcing the ice particle connections in ice layers prepared in the laboratory, comparable strength values are obtained. The presented methodology enables measurement of ice layer strength and comparison at different facilities as well as conducting advanced experiments with realistic ice layers in a laboratory environment.

A computational study of particle dynamics in synthetic jet flow field

This computational study aims to investigate the transport and dispersion of solid particles in a synthetic jet flow field. Solid spherical particles were injected into the jet at a single point, and their behavior was observed until they left the domain. The interaction between the particles and the vortex rings in the jet was compared for synthetic jets, with different Strouhal numbers (0.05, 0.1, and 0.2). The Reynolds number (Re = 150), the mass of injected particles, particle diameter distribution, and particle Stokes number at injection were kept constant. The results showed that the jet's momentum mainly transported the particles, while the vorticity of the vortex rings caused them to spread. The particle Stokes number affected the distribution of particles within the jet, with a higher Stokes number particle concentrating at the jet's center and lower Stokes number particles being carried within the vortex ring. For the low Strouhal number jet, the combined effect of the fast decline in the particle Stokes number, low vorticity of vortex ring, significant distance between successive vortices, and high jet momentum resulted in a higher spread of particles and rapid transport across the domain. As the Strouhal number increased, the particle Stokes number decreased slowly downstream; moreover, the vorticity of the vortex ring increased, the distance between vortices decreased, and low momentum imparted by the jet led to less particle spread and slower transport. Overall, the spread and transport of particles were most effective in the synthetic jet, with the low Strouhal number.

Mesoporous LaNi1-xMnxO3 perovskite with enhanced catalytic performance and coke resistance synthesized via glycine-assisted spray pyrolysis for methane dry reforming

LaNiO3 perovskite is of great interest as a catalyst for methane dry reforming. Partial substitution of Ni with Mn can improve structural stability and lower carbon deposition. In this study LaNi1-xMnxO3 perovskite (x = 0, 0.4, and 1) was synthesized using glycine-assisted ultrasonic spray pyrolysis to modify the morphology of the product, which improved the overall performance of the catalyst in the methane dry reforming. Glycine combustion in the pyrolysis process significantly increased the catalyst specific surface area and it also changed the morphology from sub-micron solid spherical particles to hollow or shell-like particles. Mn significantly stabilized the perovskite structure and in the LaNi0.6Mn0.4O3, exsolved Ni nanoparticles decorated a perovskite substrate. Mn also increased the basic sites and helped to remove the carbon deposition. The lattice oxygen in the perovskite substrate can react with the deposited carbon and as a result, virtually no carbon was observed in the time-on-stream experiments at 700 °C and 20 h. The combined effect of Mn addition and the morphological features of the glycine-assisted perovskite resulted in significant improvement of the CH4 and CO2 conversion and stability of the catalyst.

Slurry preparation for semi-solid metal direct writing by a novel approach of mixed powder remelting

Extrusion-based metal direct writing is a promising metal additive manufacturing technology due to its high efficiency and low cost. However, fabricating parts with high integrity and complex geometry remains challenging. The most critical factor is the unavailable of semi-solid slurries with uniform and nearly spherical solid particles, resulting in uncontrollable extrusion and printing. Currently, mixed powder remelting (MPR) is reported to preset the features of the solid phases, including volume fraction, morphology, and size distribution. Specifically, the semi-solid slurries of hypoeutectic AlSi alloys were obtained by preheating and shearing the mixed powder composed of eutectic AlSi alloy powder and pure aluminum powder. Their microstructural characteristics and rheological behavior were investigated, demonstrating the microstructure tailoring (controllable solid fraction and size distribution, high shape factor of about 0.9) and the reduced viscosity fluctuation by a factor of 7 compared with traditional processes. MPR shows unparalleled advantages for further engineering applications of metal direct writing.

On the dissolution of a solid spherical particle

The dissolution of a solid spherical particle is a canonical problem that finds many areas of application. In this work, we provide a generalized theory that takes into account the role of forced convection in the solvent (or, alternatively, the relative motion of the particle in the solvent), showing that the problem can be formulated in terms of four dimensionless parameters. Focusing on the case when one of these (the Reynolds number) is small, we consider asymptotic and numerical approaches to the problem, with a key outcome being a numerical method, implemented in the finite-element software Comsol Multiphysics, that is able to solve the resulting axisymmetric moving-boundary problem, even when over 90% of the particle has dissolved and its shape is far from spherical. We also demonstrate how this approach relates to and supersedes earlier efforts, providing a quantitative assessment of the often unquestioningly used Ranz–Marshall correlation for mass transfer from a sphere. In particular, we find that this correlation may overpredict the dissolution time by a factor of four, whereas a correlation by Clift et al. that is cited and used less often performs considerably better, even in the highly convection-dominated regime for which it was not originally intended.

Motion through a viscous liquid sphere enclosed by a solid core embedded into a Brinkman medium

AbstractThe flow around a solid spherical particle encased in a Newtonian liquid sphere and immersed in a couple stress fluid medium is studied. The problem is expressed by using the Brinkman and Stokes equations, which describe both the flow outside and inside the liquid sphere, respectively. The Gegenbauer polynomials and modified Bessel function are used to express the stream function solution for the internal and external regions. An analytical determination for the flow field in terms of stream function is examined by wielding the method of separation of variables. The drag force on a solid spherical particle placed in a permeable region is calculated. On the drag coefficient, the effects of the permeability κ, the viscosity ratio γ2, and the couple stress parameter λ are investigated. Corresponding dependencies (such as the permeability parameter, couple stress parameter, viscosity ratio, and separation parameter) are graphically represented and discussed. The findings shows when the separation parameter is increased the drag coefficient gradually increases, it refers to a sphere surface with a high level of flow resistance. Passages to the limits are used to describe known specific cases. The present study is essentially significant in the course through a layer developed by penetrable particles and has very important and persuasive applications both in nature and innovation, with various potential outcomes. Thus, the discoveries of this article are comprehensively pertinent to the investigation of the flow of permeable liquids past spherical permeable rocks, aloxite materials, sand beds, earthen soil, petrol supply rocks, and so forth. The present application will support in planning a productive bearing framework.

Particle laden flows around a circular cylinder from the hydrodynamic to granular regime

The flow around a circular cylinder is studied with the presence of solid finite-size spherical particles. The simulations of suspension flows are based on highly efficient simulation algorithms to generate scalable Lattice Boltzmann Method calculations. Simulations of particle resolved dynamics with up to 4800 million grid cells and 1.8 million spherical particles are carried out for different flow regimes and particle concentrations (from dilute, 5% volume concentration to semi-dilute regime, 20%). We investigated a range of parameters that spans from suspensions of iso-dense particles to highly inertial particles in a granular flow, while considering particle to cylinder diameter ratios of 5 and 10.The flow response is described by characteristic properties such as vortex shedding frequency or wake recirculation length. Flow regimes with iso-dense particles can be rationalized by means of mixture material properties while we observe a progressive transition to granular flow for inertial particles. Drag and lift forces acting onto the cylinder are presented in time and frequency domains and the physical analysis is based on the respective hydrodynamic and particle collision contributions.