Influence Of Particle Shape Research Articles

Flow Behavior of Complex-Shaped Particle Mixtures in Rotary Drums: A DEM Study

Metal matrix composites hold great potential as functional materials for energy conservation applications. These composites are manufactured using powder metallurgy, which involves the incorporation of fine particles with diverse shapes. Understanding the flowability of particle mixtures with varying shapes is crucial for optimizing industrial processes. This study focuses on analyzing the flowability and flow behavior of mixtures composed of alumina and aluminum alloy particles using the discrete element method. The particle shapes are modeled to closely resemble actual particles, and their flow behavior in a rotating drum is simulated. The upper and lower dynamic angles of repose, outlines of particle bed surface, particle displacements, and particle velocity distributions were analyzed to understand the flow characteristics of complex-shaped particles. The results reveal the influence of particle shape on the flow behavior of powder mixtures, providing valuable insights for process optimization and design.

Movement behavior of char particles in a bubbling fluidized bed at high temperature – The influence of particle shape

The movement of fuel particles has a strong effect on the spatial distribution in fluidized bed boilers, not only due to the resulting fuel mixing patterns but also to the impact on fuel conversion rate (through varied bed-fuel mass and heat transfer fuel). Thus, understanding the movement of char particles becomes critical in order to control the temperature and combustion characteristics of fluidized bed boilers. Further, the preferred orientations exhibited by non-spherical fuel particles are known to influence their motion. In this study, we developed (including experimental validation) a CFD-DEM framework to investigate the movement behavior (both translational and rotational) of a single char particle under combustion conditions (i.e. high temperature) in a fluidized bed. The work studies how the char movement is influenced by the fluidization velocity and the char particle shape: spherical (as typically adopted in modeling studies) vs. non-spherical. For non-spherical char particles, the impact of applying different degrees of particle homogeneity (glue index) in the modeling was also studied. The metrics applied to evaluate the char particle movement behavior were spatial distribution and linear and rotational velocity of the particle.The results show that the movement of spherical char particles is generally more vigorous than that of non-spherical ones. An increase in fluidization velocity yields a higher probability of populating the splash zone instead of the bed surface, due to the enhanced bubble flow. Increased fluidization velocity yields also higher rotational velocity (especially for non-spherical particles, for which the orientation angle distribution becomes eventually evenly distributed).

Particle Shape Influence in Magnetic Behavior of Pure and 3.0% Mn-doped CuO Nanofibers.

Particle Shape Influence in Magnetic Behavior of Pure and 3.0% Mn-doped CuO Nanofibers.

Fast image processing method for coal particle cluster box dimension measurement and its application in diffusion coefficient testing

The diffusion coefficient is the key parameter used to characterize methane diffusion behavior in coal. The commonly used analytical solutions for diffusion coefficients require simplifying the particle shape to regular shapes, which greatly deviates from the actual shape of coal particles. The influence of coal particle shape on the diffusion coefficient is currently not well understood. Based on image processing techniques and inverse problem-based numerical simulation, a new method is proposed in this paper to determine the diffusion coefficients of irregular coal particles, and a feasible solution for quantitatively assessing the influence of particle shapes on the diffusion coefficient is provided. The implementation of this method is based on two aspects: the fast quantitative characterization of the shape features of coal particle clusters and inverse problem-based numerical simulation to solve the diffusion coefficient of irregularly shaped coal particles. First, image processing technology is used to quickly and accurately extract the 2D projection contour of batch particles, and an algorithm based on fractal theory is designed to obtain the box dimension of batch contours, which achieves the quantitative characterization for the shape features of coal particle clusters. At the same time, a comparison with Fraclab is conducted to validate the scientific effectiveness of the box dimension algorithm. Then, 3 coal particles with representative fractal dimensions are selected and their diffusion coefficients are obtained using the inverse problem numerical method. The results indicate that the desorption curves obtained through inverse problem optimization for the 3 particles are excellently consistent with the experimental data, with fitting degrees R2 all exceeding 99%. Therefore, the diffusion coefficients can be effectively obtained. Meanwhile, the influence of shape on the diffusion coefficient is analyzed quantitatively. The results show that the diffusion coefficient increases with the box dimension of the contour, and the particle shape has a considerable impact on determining the gas diffusion coefficient.

Analysis of hydraulic conditions considering the influence of particle shape

Analysis of hydraulic conditions considering the influence of particle shape

Morphology of impact fragmentation distribution of single spherical and ellipsoidal particles in drop weight experiments

Particle shape is an important factor affecting the fragmentation distribution of the ore particles. To investigate the influence of particle shape on the morphological fragmentation distribution characteristics, the crushable ore particles are defined as prolate, oblate ellipsoid and spherical particles, which have different aspect ratios (AR) and sphericity (S). Based on the drop weight experiment, the influence of the net drop height on the macroscopic mechanical behavior and crushing distribution characteristics of the single spherical and ellipsoidal particles is studied. The results show that different peak-shifting characteristics exist during particle fragmentation. The fragmentation distribution peak shifts left when the increased impact energy is eventually only enough to break medium-sized sub-particles. Conversely, it shifts right when impact energy is increased enough to break largest-sized sub-particles. Besides, regardless of whether the net drop height changes, the maximum continuous fragmentation degree presents “M”-shaped characteristic with the increased AR. Compared with the ellipsoid particles, the single spherical particle is more difficult to be broken by impact, with wider equivalent particle fragmentation distribution. With the increase of particle sphericity, the maximum continuous fragmentation degree of a single ellipsoid particle has an overall trend of initial increase and subsequent decrease. Especially when particle sphericity is 0.9 < S < 0.95, the maximum continuous fragmentation degree of both prolate and oblate ellipsoid particles is much higher.

Study of cone penetration test in granular soil considering realistic particle shapes by discrete element method in 3D

This paper aims to investigate the impact of the particle shape of granular soil particles on the results of cone penetration test (CPT). The discrete element method (DEM) was used to model the CPT in soil particle samples in 3D. The influence of particle shape is studied by parameters of overall regularity (OR), which is obtained from different mixing ratios of the real shape particles and spherical particles. The real particle shapes are obtained from a 3D laser scanner for the simulations. The particle refinement method is applied to enhance computation efficiency. The cone resistance and sleeve resistance curves are smoothed by fitting equations. The factors of OR of soil, particle friction coefficient, particle roundness and initial porosity were demonstrated to have considerable influences on the cone tip resistance and sleeve resistance. The displacement field and the rotational field were plotted to study the microscopic behaviour of granular soils during the penetration process.

Efficiency analysis and optimisation of DEM for railway ballast track simulations: Multi-layer shape model of lateral resistance

The railway ballast layer provides the function of bearing loading, resisting geometry degradation, and drainage. In those related research, the behaviour of ballast assembly can be obtained by laboratory (or in-situ) tests. Limited simulation methods can be used to analyse the behaviour of ballast particles at the mesoscopic level. The numerical simulations based on the Discrete Element Method (DEM) are employed, which treat every ballast particle as a calculation component. However, the efficiency of DEM simulation is very low due to the algorithm and a very large number of elements. This paper analysed the efficiency-related questions of the DEM modelling. The influence of particle shape and contact properties on the force behaviour is studied. Further, an optimised multi-layer ballast track model is introduced based on the most influential ballast areas. In such areas, particles are generated with an irregular shape to ensure the reliability of results, and particles except that area are generated with a rolling resisted ball shape to decrease the number of elements. A series of lateral resistance simulations are conducted to show and validate the accuracy and efficiency of this method in the dimension of the single sleeper section. Results show that this optimised multi-layer model building method largely improves efficiency, and it can provide accurate data.

Influences of Ferric Ions and Fe as a Minor Element in the Lattice on the Floatability of Cassiterite.

In this study, synthetic pure cassiterite and cassiterite doped with two different Fe contents were successfully recrystallized by means of sintering. Their crystal structure and chemical compositions were characterized by X-ray powder diffraction (XRD) as well as scanning electron microscopy (SEM) combined with energy-dispersive X-ray (EDX) analysis. Their floatability was studied by microflotation with a diphosphonic acid surfactant named Lauraphos301 as a collector. Unlike the addition of ferric ions in solution, which strongly depressed the floatability of all of the cassiterite samples, a much higher flotation efficiency of the Fe-doped cassiterite samples was found especially at lower collector concentrations. The cassiterite floatability is proportional to the Fe content in cassiterite at a broad range of pH, and the recovery has the following order: cassiterite with 1417 ppm Fe > cassiterite with 1165 ppm Fe > pure cassiterite. The electrokinetic behavior of the cassiterite samples with and without the collector was studied by electrophoretic measurements and revealed that the chemical interaction dominated the adsorption. With the help of the particle shape analysis, a more angular shape was found for the Fe-doped cassiterite samples. Moreover, without the influence of particle shape, much abundant adsorption of Lauraphos301 was found on the Fe-doped cassiterite samples by AFM topography imaging. The minor amount of Fe in the cassiterite lattice and a more angular shape of the Fe-doped cassiterite samples were believed to enhance floatability collectively. The study reveals that the influence of the chemical composition of the minerals on flotation was almost inextricably bound up with particle morphology and emphasizes the importance of considering both factors and investigating them individually for the flotation study.

Improved method for generating sand assembly with wide range of aspect ratios and angularities based on insights gained from comparative study of existing techniques

The generation of realistic sand assemblies with a wide range of particle shapes is important for investigating the influence of particle shape on the microscale and macroscale mechanical behaviors of sands using the discrete element method. The major contribution of this study is the development of an improved technique for such assemblies. The method generates sand assemblies with a wide range of aspect ratios and angularities and retains the particle size effects and major morphological characteristics of the original particles. First, based on the insights gained from a comparative study of existing techniques, a method that integrates principal component analysis (PCA) with coefficient standardization is selected as the basic framework for particle generation. Second, by expanding the spherical harmonics (SHs) of the compensation radii between particles and their circumscribed super-ellipsoid surfaces, a new method that can extract the aspect ratio characteristics of sand particles is proposed for particle reconstruction. Finally, a method integrating the SH expansion of the compensation radius, PCA, and coefficient standardization is formulated and demonstrated to be efficient in generating sand assemblies with a wide range of aspect ratios and angularities.

The interplay between size, shape, and surface segregation in high-entropy nanoalloys.

The respective influences of particle shape and size on the energetic stability of five-component multimetallic nanoparticles have been computationally investigated for AlCuFeCrNi and AuCuPdNiCo mixtures at equiconcentration. Using available embedded-atom model potentials, exchange Monte Carlo simulations possibly assisted with systematic quenching, we explore tools to approach ideal phase equilibrium in such high-entropy nanoalloys. In particular, we show how deviations to ideal solid solution behaviors can be characterized using percolation analyses, and how the contribution of alloying fluctuations at finite temperature can be inferred to evaluate the entropy of mixing in such nonideal cases. An approximation to the entropy of mixing based on pair correlations only is also found to capture the behavior of the thermodynamical mixing entropy quite well, and can be used as an order parameter of mixing. While the AlCuFeCrNi mixture appears to mix reasonably well in all cases considered, cobalt and nickel segregate significantly in AuCuPdNiCo nanoparticles, deviating strongly from ideal random mixtures. A simple Gaussian regression model applied to a coarse distribution of concentrations is found to correctly predict conditions for optimising the mixing thermodynamical properties of the miscible AlCuFeCrNi nanoparticle.

Effect of Particle Shape on Parameter Calibration for a Discrete Element Model for Mining Applications

The discrete element method (DEM) has been widely employed to model processes in different industries, such as mining, agriculture, pharmaceuticals, and food. One of the main lines of research, and in which different authors propose several approaches, is the calibration of parameters. Bulk calibration (BCA) is a common approach used that does not necessarily represent the individual behavior of each particle. On the other hand, direct measurement (DMA) is another approach employed in some cases. This work presents a comparison between calibration of DEM model parameters with non-cohesive spherical and polyhedral particles using a combination of direct measurement and bulk calibration. BCA is employed to calibrate friction parameters and DMA to characterize shape of the particles and coefficient of restitution of the contact between particles. Experimental data from Draw Down Tests are used to calibrate the friction parameters. Numerical optimization of the parameters is conducted by altering the coefficients of friction regarding the objective variables of mass flow, final mass, shear angle, and angle of repose. Quartz, granite, and coal are calibrated, obtaining good agreement with the experimental results. The influence of particle shape is tested, proving that more complex particles obtain better results for the analyzed case.

Influence of Particle Shape on Tortuosity of Non-Spherical Particle Packed Beds

Tortuosity in packed beds or porous media is of significant interest in many fields, from geoscience to the chemical industry. Tortuosity plays a significant role in the mass transport in porous media, but also in their residual thermal or electric conductivity when the particles are not conducting. Several predictive models have been proposed to evaluate tortuosity, but there is still a gap when it comes to considering various particle shapes. The preponderance of tortuosity models substantiated in the literature are porosity-dependent while only a few include shape parameters. In this work, we propose a new model with sphericity and porosity to predict the tortuosity based on thermal simulations carried out with non-conducting particles for domains with no wall effect. The beds generated from rigid body simulations are compared and studied for different particle shapes with a sphericity range of 0.65–1. Sphericity showed a significant effect on the tortuosity compared with other 3D shape parameters (numbers of faces, edges, and vertices); therefore, only sphericity has been considered in the new model. The proposed new model is well suited for the porosity range of 0.3 to 0.4. In said ranges, it is an upgrade of the classical Zehner–Bauer–Schlünder (ZBS) model for the effective thermal conductivity of packed beds, with superior performance.

Combined Influence of Particle Shape and Fabric on the Shear Behaviour of Granular Materials

The anisotropy feature is an important characteristic of granular materials in natural life and is caused by two facts: the anisotropy feature of particle shape, such as an elongated or flattened shape, and the anisotropy feature of the packing fabric, such as the preferable orientation of particle alignment. The discrete element method has been commonly used in the study of meso-mechanics of granular materials and is in our study to simulate the direct shear test with particles of various aspect ratios under different initial orientation alignment conditions for assessing the coupled influence of anisotropy from particle shape and fabric of particle packings on the shear behaviour of granular materials. Analysis results show that anisotropy from the particle shape has the most significant influence on the shear behaviour of a granular packing when the packing has the initial anisotropy fabric of an orientational alignment perpendicular to the shear direction. Moreover, the initial fabric anisotropy of a granular packing has an increasing influence with the rise in anisotropy of particle shape. A combined anisotropic factor is finally introduced to reflect the coupled influence of the shape anisotropy of particles and the fabric anisotropy of particle packings.

A terminal-velocity model for super-ellipsoidal particles

The prediction of the terminal velocity of non-spherical particles, such as sediments and microplastics, is essential for understanding their transport processes in rivers or marine environments. However, most of the existing models have been proposed based on specific particle materials, and there is a lack of systematic research on the effects of different shape factors on terminal velocity. In this study, super-ellipsoidal particles were selected as test particles for settling experiments, and a particle–velocity tracking code was developed to measure their terminal velocities during falling through glycerin–water mixtures. A terminal–velocity model for super-ellipsoidal particles was proposed based on the measured data. Owing to the new model, multivalued predictions of the terminal velocity based on a single shape factor, such as sphericity and Corey shape factor, were disclosed, and the prediction errors were evaluated. The results of this study can provide a basis for establishing a general terminal–velocity model that considers the influence of particle shape.

Influence of particle shape on the interaction processes of coal particles and bubbles in saline solution

Understanding the role of coal particle shape in the flotation process is helpful in achieving a clean usage of coal slime flotation. In this investigation, the anthracite coal surface was modified using a chlorinated salt solution containing Na+, Ca2+, or Fe3+. Coal particles with four surface shapes were prepared: angular coal particles (ARPs), prismatic coal particles (PCPs), flat coal particles (FTPs), and spherical coal particles (SLPs). The ARPs were subdivided into five kinds of curvature: 3π/2, 21π/20, 7π/11, π/3, and π/10, and the PCPs were subdivided into five kinds of dihedral angles: 30°, 60°, 90°, 120°, and 150° according to the surface flatness of the ARPs and PCPs. Six ion concentrations, of 0, 5, 10, 20, 40, and 80 mmol/L, were examined. We tested the liquid film drainage time (LDT), maximum repulsive force (MRF), and maximum attractive force (MAF) between these coal particles and bubbles. The results show that at a constant solution concentration for a particular particle shape, the MRFs and LDTs increase in the order of Fe3+<Ca2+<Na+, and the MAFs decrease in the order of Fe3+>Ca2+>Na+. This indicates that Fe3+ enhances the adhesion probability and stability of anthracite particles and bubbles by the greatest extent, followed by Ca2+ and Na+. For a particular shape of coal particles, an increase in the ion concentration reduces the LDT and MRF and increases the MAF. When the curvature of the ARPs is 3π/2 and the dihedral angle of PCPs is 30°, the order of the LDTs of coal particles and bubbles is ARP < PCP < SLP < FTP. With a decrease in the curvature of ARPs and an increase in the dihedral angles of PCPs, their LDTs gradually approaches that of the FTP. The results for MRF and MAF are consistent with the LDT. Therefore, the ARPs with larger curvature and PCPs with smaller dihedral angles easily attach to air bubbles, and the decrease of the curvature and the increase of dihedral angles hindered the detachment. Adhesion and detachment experiments were conducted to confirm these results. The coal particles had a tendency to contact the bubbles with their available tips while sliding on the surfaces of bubbles to induce liquid film rupture. In addition, regardless of the coal particle shape, increasing ion concentration changes the detachment position of coal particles. These findings are consistent with the results of LDT, MRF, and MAF measurements. In this study, the role of coal particle shape in saline solution were systematically investigated, which provides a possible solution for the problems caused by the presence of ions in the flotation process using saline as the water source.

DEM contact model for spherical and polyhedral particles based on energy conservation

The mechanical behaviors of granular materials are greatly influenced by the geometric shapes, which is widely investigated using the discrete element method (DEM). Accurate contact detection is a critical issue in modelling complicated contact types, especially for arbitrary shaped particles. In this study, the contact detection algorithms for spherical and polyhedral particles based on energy conservation are classified into polyhedron-polyhedron and sphere-polyhedron contacts. The polyhedron-polyhedron and sphere-polyhedron contact detection algorithms are developed under the DEM framework of Coupling Simulator (CoSim-DEM). Geometric dualization theory is used in the polyhedron-polyhedron contact detection algorithm to construct the overlapping volume of polyhedral particles. For the sphere-polyhedron contact detection, the algorithm can transfer into the contact between sphere and triangles composed of polyhedron, and the contact forces between arbitrary shaped particles can be calculated based on calculated contact characteristics. Particle collision tests with different particle shapes and contact types are used to validate the aforementioned algorithms. Experiments and simulation studies of deposition tests are conducted to validate the effectiveness and stability of algorithms. Furthermore, the rotating drum tests are used to analyze the influence of particle shapes on the calculation efficiency. Finally, a large-scale rotating drum test involving different kinds of particles with random sizes is performed, demonstrating the robustness of algorithms based on CoSim-DEM.

Modeling of Particle Dissolution Behavior Using a Geometrical Phase-Field Approach.

Material dissolution is a critical attribute of many products in a wide variety of industries. The idealized view of dissolution through established prediction tools should be reconsidered because the number of new substances with low aqueous solubility is increasing. Due to this, a fundamental understanding of the dissolution process is desired. The aim of this study was to develop a tool to predict crystal dissolution performance based on experimentally measurable physical parameters. A numerical simulation, called the phase-field method, was used to simultaneously solve the time evolution of the phase and concentration fields of dissolving particles. This approach applies to diffusion-limited as well as surface reaction-limited systems. The numerical results were compared to analytical solutions, and the influence of particle shape and interparticle proximity on the dissolution process was numerically investigated. Dissolution behaviors of two different substances were modeled. A diffusion-limited model compound, xylitol, with a high aqueous solubility and a surface reaction-limited model compound, griseofulvin, with a low aqueous solubility were chosen. The results of the simulations demonstrated that phase-field modeling is a powerful approach for predicting the dissolution behaviors of pure crystalline substances.

Measuring the Effect of Pack Shape on Gravel’s Pore Characteristics and Permeability Using X-ray Diffraction Computed Tomography

Particle shape is one of the critical parameter factors that affect gravel’s pore structure and permeability. However, few studies have considered its effects on engineering applications due to the difficulty of conducting laboratory tests. To overcome these difficulties, new methods of estimating the gravel pack shape that involve manual work and measuring the surface area of particles and pores based on support vector machine segmentation and the reconstruction of X-ray diffraction computed tomography (CT) images were proposed. Under the same conditions, CT tests were carried out on gravel packs and two other regular-shaped particle packs to investigate the influence of particle shape on the fractal dimension of gravel’s pore–particle interface and the specific surface area of the pore network. Additionally, permeability tests were performed to study the effect of particle shape on gravel’s hydraulic conductivity. The results showed that a gravel pack with a larger aspect ratio and a smaller roundness had a larger specific pore network surface area and a more complex pore structure, leading to lower permeability. This kind of gravel had a more significant length, quantity, and tortuosity of the seepage path when seepage occurred in a two-dimensional seepage field simulation. Therefore, we suggest that the filter materials of hydraulic projects should preferably use blasting gravel with a larger aspect ratio and smaller roundness to achieve better anti-seepage properties. In addition, projects can increase pores’ specific surface area using our method as a control factor in filter construction.

Influence of particle shape and material on the acoustic radiation force and microstreaming in a standing wave.

In view of its influence on the acoustic radiation force, we investigate the microstreaming around a small solid elastic particle in an ultrasonic standing wave in dependence of its material properties and shape. The configuration is axisymmetric, making it accessible to numerical methods, such as the finite element method. The results reveal a transition from viscous scattering- to microstreaming-dominated acoustic radiation force that depends on the particle density. When a deviation of the particle shape from a sphere becomes smaller than the viscous boundary layer thickness, we show that the influence of the shape on the viscous contributions to the acoustic radiation force diminishes, allowing the use of theoretical models for a spherical particle. However, extreme asymmetric shape perturbations, such as crowns with sharp edges, can give rise to noticeable viscous contributions for a dense particle that is larger than the viscous boundary layer thickness. We also introduce a hybrid analytical model for the acoustic radiation force on a spherical particle that accounts for the microstreaming and particle compressibility and shows a good agreement with numerical simulations for an arbitrary particle size and density.