Influence Of Particle Shape Research Articles

Exploring disordered packing of non-equant particles: Insights from computed tomography and Monte Carlo simulations

The influence of particle shape on disordered packing structures is investigated through a combined experimental and modeling approach, focusing on non-equant particles, i.e. particles which are either elongated or flat, or both. In an experimental campaign, particles of systematically chosen shapes are fabricated via 3D printing, then packed and imaged by X-ray Computed Tomography to extract packing properties such as the porosity, particle orientations, and tortuosities of paths through the pore space. Additionally, a Monte Carlo model is employed to simulate packing structures, allowing for broader exploration of the parameter space, and investigating properties which are challenging to measure experimentally. The model’s parameters are varied to probe the range of potential packing structures for various particle shapes, and to provide explanations for experimental results. Both model and experiments reveal a non-monotonic trend for the porosity, a monotonically decreasing trend for the average particle inclination, and a monotonically increasing trend for the tortuosity with respect to elongation and flatness. Additionally, both model and experiments show increased dependence of the packing properties on the packing method (pouring or shaking), or model parameters respectively as particle aspect ratio increases. Furthermore, the model can predict experimentally measured packing porosities with deviations of 0.03 in absolute porosity units at most for new particle shapes, once its parameters are fitted to match the physical context. This research provides insights into the effect of particle shape on packing structure, with practical implications to processes involving the packing of non-equant particles, such as crystal filtration and packed beds.

Investigating the influence of particle shape on discrete element modeling of granular soil under multidirectional cyclic shearing

In this study, a series of undrained multidirectional cyclic simple shear tests were conducted using the discrete element method. Various stress paths, including figure-8, circular, teardrop, and straight-line shapes, were considered. Realistic and irregular particles were generated by integrating the theory of random fields for spherical topology with the Fourier-shape-based method. The influence of particle shape irregularity was assessed using a synthetic parameter derived from four common descriptors: aspect ratio, roundness, convexity, and sphericity. The study revealed that the liquefaction resistance of samples subjected to a constant cyclic shear stress ratio predominantly depended on the stress trajectory and particle shape. Numerical results demonstrated that the sample undergoing the unidirectional simple shear exhibited the highest liquefaction resistance, whereas the figure-8 shape exhibited the lowest. Furthermore, greater irregularity in particle shape corresponded to increased resistance to failure. Additionally, microstructural evolutions of granular samples were quantified throughout the simulation using the contact-normal-based fabric tensor. This allowed for a comprehensive exploration of the interplay between internal structure and external loading, leading to a more comprehensive understanding of the macroscopic observations discussed above.

Influence of particle shape on erosive wear in liquid-solid two-phase flow of blackwater angle valves

The main cause of erosive wear of blackwater angle valves in coal gasification systems is the collision and friction of particles with the valve wall. The parameters of particle-valve wall collision can be significantly affected by particle shape. In this study, the effect of particle shape on spool and body wear in blackwater angle valves used in coal gasification was numerically investigated using the CFD-DEM method. The relationship between particle shape and valve wear was fitted using a cubic polynomial. The results of the study can be used as a guide when designing blackwater valves.

Cuboids Prevail When Unraveling the Influence of Microchip Geometry on Macrophage Interactions and Metabolic Responses.

Drug delivery advances rely on using nano- and microsized carriers to transfer therapeutic molecules, although challenges persist in increasing the availability of new and even approved pharmaceutical products. Particle shape, a critical determinant in how these carriers distribute within the body after administration, raises opportunities of using, for instance, micrometer-sized nonspherical particles for vascular targeting and thereby creating new prospects for precise drug delivery to specific targeted areas. The versatility of polycrystalline silicon microfabrication allows for significant variation in the size and shape of microchips, and so, in the current work, photolithography was employed to create differently shaped polysilicon microchips, including cuboids, cubes, bars, and cylinders, to explore the influence of particle shape on cellular interactions. These microchips with different shapes and lateral dimensions, accounting for surface areas in the range of ca. 15 to 120 μm2 and corresponding total volumes of 0.4 to 27 μm3, serve as ideal models for investigating their interactions with macrophages with diameters of ca. 20 μm. Side-scattering imaging flow cytometry was employed for studying the interaction of label-free prepared microchips with RAW 264.7 macrophages. Using a dose of 3 microchips per cell, results show that cuboids exhibit the highest cellular association (ca. 25%) and uptake (ca. 20%), suggesting their potential as efficient carriers for targeted drug delivery to macrophages. Conversely, similarly sized cylinders and bar-shaped microchips exhibit lower uptakes of about 8% and about 6%, respectively, indicating potential benefits in evading macrophage recognition. On average, 1-1.5 microchips were internalized, and ca. 1 microchip was surface-bound per cell, with cuboids showing the higher values overall. Macrophages respond to microchips by increasing their metabolic activity and releasing low levels of intracellular enzymes, indicating reduced toxicity. Interestingly, increasing the particle dose enhances macrophage metabolic activity without significantly affecting enzyme release.

Elucidating the impact of non-spherical morphology on kinetic behavior of graphite using single-particle microelectrode

The precise assessment of the kinetic properties of graphite is crucial for the design of the material and the development of electrochemical models for lithium-ion batteries. However, conventional evaluation methods using composite electrodes fall short in excluding the influence of its porous structure and evaluating the influence of particle shape on kinetic behavior. In this work, we elucidate the impact of non-spherical morphology on kinetic behavior of single artificial graphite particle, employing the single-particle microelectrode technique. Three single artificial graphite particles with different sizes are pre-cycled and exhibit outstanding rate capability, maintaining a maximum capacity retention of 78.1 % at 200 C. Further, exchange current density and diffusion coefficients are determined through Tafel plots and the potentiostatic intermittent titration technique (PITT), respectively. It is found that the particle with a higher exposure of edge planes present elevated exchange current density and diffusion coefficients. Considering that the graphite particles typically feature an ellipsoidal rather than spherical shape, we propose an approach based on an ellipsoidal diffusion model for extracting diffusion coefficients. This model takes into account the non-spherical morphology of graphite, addressing the limitations inherent in the geometric assumptions of previous methods. The average relative error between the diffusion coefficients derived from the ellipsoidal diffusion model and the previous method using spherical assumptions is 215 %, indicating that accurately depicting the shape of ellipsoidal graphite particles in the model is crucial for obtaining correct estimates of kinetic parameters. This study offers direct experimental evidence of superior kinetic behavior of edge planes over basal planes. To leverage this characteristic, it is recommended to employ an out-of-plane aligned architecture for composite electrodes using novel techniques, e.g., 3D printing or magnetic alignment techniques.

Magnetic Metalloimmunoassays: Influence of Particle Shape and Size on Galvanic Exchange-Based Electrochemical Detection

The electrooxidation of silver (Ag) offers improved signal sharpness and intensity, enabling precise measurements and enhanced resolution in electrochemical sensing. Leveraging silver nanoparticles (AgNPs) as indirect labels in electrochemical assays provides a distinct advantage for detecting various biomarkers at clinically relevant concentrations. In our recent work, we have introduced an electrochemical approach that involves a galvanic exchange (GE) reaction between electrodeposited gold and AgNPs, followed by anodic stripping voltammetry (ASV), with potential applications in immunosensing. In this assay protocol, specific monoclonal antibodies immobilize the biomarker of interest separately on AgNPs and magnetic beads. Subsequently, magnetic bead-AgNP conjugates are attracted to the electrode surface by a magnetic force. However, to achieve the expected analytical performance of the bioassay, it is imperative to characterize the composition, size, shape, and surface modifications of the AgNPs. Consequently, our research focuses on investigating the electrochemical properties of a model bioconjugate formed between magnetic microbeads (MB) and AgNPs through Streptavidin-biotin interactions under various assay conditions. Notably, our recent studies reveal that conducting the GE cycle for three repetitions significantly enhances the Ag signal, yielding an improvement of approximately two-fold or greater compared to previously reported methods. Previous studies have shown that altering the shape of AgNPs, transitioning from nanospheres to other forms like nanocubes and nanodisks enhances both the limit of detection and the range of analyte detection. However, despite these enhancements, spherical AgNPs remain the most stable and easily synthesized option, characterized by excellent homogeneity. Recently, we compared AgNPs with diameters ranging from 20 to 100 nm paired with magnetic microbeads with diameters spanning from 50 nm to 3 µm to identify the optimal combination. Preliminary results indicate that the Mb (3 µm)-AgNP (50 nm) conjugate exhibits the highest Ag charge and Ag collection efficiency. Nonetheless, critical knowledge gaps persist regarding the fundamental understanding of the electrogenerated GE process and we are continually working on refining the electrochemical and assay parameters to develop a robust universal platform for GE-based electrochemical immunosensing.

Quantifying the influence of single particle shape on crushing characteristics of recycled aggregates: Experimental and numerical insights

Exploring the interplay between shapes and crushing characteristics of recycled aggregates (RA) is pivotal for understanding their macro-mechanical behavior in bulk materials. This investigation quantitatively characterizes the shapes of recycled bricks (RB), recycled concrete (RC), and recycled mortar (RM) particles, and assesses their single-particle crushing characteristic. Key focus areas include the analysis of crushing modes, fractal attributes, strength, and energy, supplemented by a comparative study using discrete element method (DEM) simulations to predict outcomes for particles of specific sphericity. Findings reveal that the shapes of RA particles are mainly disk, block, blade and bar, with particle size showing negligible influence on these forms. Crushing behaviors are categorized into penetrating fracture, corner rupture, and overall fragmentation, closely linked to particle sphericity. Notably, an increase in sphericity leads to a reduction in fractal characteristics of RA, refining the gradation distribution from broad to narrow spectrums. An exponential relationship is identified between the crushing strength of RA and particle sphericity, a pattern also mirrored in the correlation between crushing energy and sphericity, thereby underscoring the significant influence of particle shape. These relationships facilitate predictions regarding the crushing strength and energy based on sphericity. While numerical simulations broadly align with experimental data, discrepancies in the crushing energy of highly spheric particles necessitate adjustments, resulting in a modified predictive equation for crushing energy. This work enriches the understanding of RA crushing behavior, offering invaluable insights for predicting the single-particle strength and deformation characteristics across different sphericities, thus advancing material engineering and recycling practices.

Experimental study on the combined influence of particle shape, density, and size on segregation behavior in binary and ternary granular mixtures

Segregation of granular materials is a common experience; however, a few studies consider the segregation of granular mixtures characterized by variations in particle shape. Additionally, many particle systems in industry and geophysics consist of nonspherical particles. In the present study, we conducted a series of experiments to investigate the influence of particle shape, density, and size on the dynamic characteristics and segregation behavior in binary and ternary granular mixtures. Our experimental findings demonstrated a noteworthy correlation between the final steady-state segregation intensity and the proportion of non-spherical beans and cube-shaped particles in a ternary granular mixture. Specifically, the presence of beans, which are larger than the other particles, in a binary and ternary granular mixture increased the size-induced segregation phenomenon. Conversely, the steady-state segregation intensity decreased as the proportion of cube particles, which were less dense but of the same volume as the other materials, increased in a ternary granular mixture, indicating a mitigation of density-induced segregation. The study also discusses the relationship among the dynamic angle of repose, dynamic properties, and segregation behavior arising from the effects of shape, size, and density in binary and ternary granular mixtures.

Compaction and shear characteristics of recycled construction & demolition aggregates in subgrade: Exploring particle breakage and shape effects

Recycling construction and demolition (C&D) wastes into useable aggregates in subgrade applications offers significant sustainability benefits. However, the characteristics of recycled aggregates, including particle morphology, crushing strength, and shear behavior, differ substantially from natural aggregates. This paper presented an extensive experimental study on the compaction and mechanics performances of recycled concrete and brick aggregates, with a particular focus on the effects of particle breakage and shape characteristics. The compaction of recycled aggregate specimens comprising three structural types was evaluated using heavy Marshall compaction (HMC) and Superpave gyratory compaction (SGC). The compaction characteristics and particle breakage were examined, enabling a profound understanding of the compaction mechanisms associated with both methods. Furthermore, triaxial shear tests were performed to scrutinize the influences of particle shape, compaction degree, and confining pressure on shear characteristics. Results showed that after 80 gyratory rotations in SGC, the compaction degree of recycled aggregates aligned with the targeted results obtained from HMC. Changes in fractal dimension after compaction exhibited direct correlations with the two-dimensional shape distribution. Axial coefficient, fractal dimension and confining pressure most strongly influenced shear strength. In light of these insights, prediction models for shear strength parameters were proposed using multiple regression analysis. Overall, the study provides valuable insights into the relationships between aggregate morphology, compaction response, breakage behavior, and shear performance. These findings can facilitate optimized design and construction using recycled aggregates to advance sustainable infrastructure development.

DEM investigation on sandy soil behaviors under the influence of particle shape

The mechanical properties of sandy soil, a prevalent material in engineering construction, are affected by several factors, including the particle shape. This study utilized a rigid block unit for particle simulation and established specimens reflecting the real particle appearance based on μCT scanning geometry. Four simple particle types with varying roundness were designed according to the roundness definition, and corresponding numerical test models were developed. These models were employed to examine the effect of particle roundness on the macroscopic mechanical properties of sandy soil using triaxial shearing simulation tests, disregarding other shape parameters. The results demonstrate that particle roundness significantly affects the mechanical properties of sandy soil. Within a roundness range of [0,1], samples with varying particle roundness displayed different deviatoric stress–strain curves. As the roundness increases, the peak deviatoric stress decreases, and both the cohesive strength and friction angle of the samples reduce.

Exploring the combined effect of particle shape and friction on cell structures in granular packings via LS-DEM modeling

To comprehensively understand and predict the macroscopic behavior of a granular system, one must consider not only the properties of individual particles but also the local structures. In this study, we prepare mechanically stable granular packings of super disks using the two-dimensional level set discrete element method (LS-DEM). We identify the cells, the irreducible loops enclosed by contacting particles, in the prepared granular packings and then analyze the statistics of these structures. We find the following. (1) The packing fraction or mean coordination number of studied systems exhibits a non-trivial dependency on particle shapes and inter-particle frictions, making it challenging to establish a direct correlation between them. (2) Using the cell-based description as a bridge, we can measure the packing behavior without considering the influence of particle shape and inter-particle friction. Specifically, the mean coordination number can be explicitly represented as a function of the mean cell order according to Euler’s topological relation. Upon the assumption that all cells are regular polygons, we can also approximately estimate the rattlers-free packing fraction via the mean cell order. (3) We have observed a nearly linear relationship between the mean cell order and rattler fraction. This enables us to determine the packing fraction as well.

Determination of interparticle radiative heat transfer and radiation absorption for ellipsoidal particle beds using Monte Carlo ray tracing

The calculation of radiative heat transfer between particles in particle-based solar systems presents significant challenges in terms of computational cost and accuracy. This study addresses these challenges by employing the discrete element method to generate random particle packings and the Monte Carlo ray tracing method to investigate the influence of particle shape and volume fraction (ϕ) on interparticle radiation transfer and the absorption of incident radiation. The results reveal that, at low volume fractions, the shape and orientation of ellipsoidal particles have a pronounced impact on direct radiative transfer. Oblate particles exhibit the highest average radiation distribution factor (RDF), and the dispersion of RDF data is more prominent for oblate and elongated prolate particles compared to spheres. As ϕ increases to 0.35, the contribution of indirect transfer from neighboring particles becomes significant for oblate particles, resulting in a reduction in the dispersion of RDF data. Furthermore, when ϕ reaches 0.55, the decisive factor in determining RDF becomes the shielding effect of particles positioned between the emitting and receiving particles. The average RDF tends to converge among particles of different shapes, although oblate and elongated prolate particles still exhibit considerably larger RDF dispersion compared to spherical and near-spherical particles. Additionally, the effective absorptivity of the particle bed for incident radiation decreases as the aspect ratio of particles increases at all volume fractions. Moreover, the transmitted fraction demonstrates an exponential relationship with the depth, and beds composed of spherical particles exhibit better radiation transmittance compared to beds containing non-spherical particles.

Integrating Experimental and Computational Analyses for Mechanical Characterization of Titanium Carbide/Aluminum Metal Matrix Composites.

This study investigates the mechanical properties of titanium carbide/aluminum metal matrix composites (AMMCs) using both experimental and computational methods. Through accumulative roll bonding (ARB) and cryorolling (CR) processes, AA1050 alloy surfaces were reinforced with TiCp particles to create the Al-TiCp composite. The experimental analysis shows significant improvements in tensile strength, yield strength, elastic modulus, and hardness. The finite element analysis (FEA) simulations, particularly the microstructural modeling of RVE-1 (the experimental case model), align closely with the experimental results observed through scanning electron microscopy (SEM). This validation underscores the accuracy of the computational models in predicting the mechanical behavior under identical experimental conditions. The simulated elastic modulus deviates by 5.49% from the experimental value, while the tensile strength shows a 6.81% difference. Additionally, the simulated yield strength indicates a 2.85% deviation. The simulation data provide insights into the microstructural behavior, stress distribution, and particle-matrix interactions, facilitating the design optimization for enhanced performance. The study also explores the influence of particle shapes and sizes through Representative Volume Element (RVE) models, highlighting nuanced effects on stress-strain behavior. The microstructural evolution is examined via transmission electron microscopy (TEM), revealing insights regarding grain refinement. These findings demonstrate the potential of Al-TiCp composites for lightweight applications.

Active spheroids in viscosity gradients

In this paper, we explore the hydrodynamics of spheroidal active particles in viscosity gradients. This work provides a more accurate modelling approach, in comparison to spherical particles, for anisotropic organisms such as Paramecium swimming through inhomogeneous environments, but more fundamentally examines the influence of particle shape on viscotaxis. We find that spheroidal squirmers generally exhibit dynamics consistent with their spherical analogues, irrespective of the classification of swimmers as pushers, pullers or neutral swimmers. However, the slenderness of the spheroids tends to reduce the impact of viscosity gradients on their dynamics; when a swimmer becomes more slender, the viscosity difference across its body is reduced, which leads to slower reorientation. We also derive the mobility tensor for passive spheroids in viscosity gradients, generalizing previous results for spheres and slender bodies. This work enhances our understanding of how shape factors into the dynamics of passive and active particles in viscosity gradients, and offers new perspectives that could aid the control of both natural and synthetic swimmers in complex fluid environments.

Simulation of non-spherical particles stirring process in stirred tanks

There are few studies on the dependence of particle suspension and dispersion on particle shape in stirred tanks. Most of the non-spherical particle problems are converted into spherical particles in the simulation process. The influence of particle shape on particle suspension and dispersion is generally ignored. Therefore, combined with the RNG k-ɛ turbulence model, the DEM-VOF method is used to simulate the suspension and dispersion dynamics of non-spherical particles in liquid-solid stirred tanks. A four-blade 45° oblique blade turbine is used in a flat stirred tank, and the impeller rotation is simulated by the sliding grid method. The effectiveness of DEM-VOF coupling method is verified theoretically and experimentally. And the results show that the particle shape has a great influence on the interaction between the fluid and particles and the distribution of particles in stirred tanks. This study provides a useful foundation for further research on the influence of particle shape.

3D printing-aided numerical study of particle shape effect on behaviours of dry granular flows interacting with rigid barriers

Particle shape plays a crucial role in determining the mobility and impact characteristics of granular flows, yet analyses of the effects of particle shape are rare. In this study, three-dimensional (3D) printing technology is used to create rock-like materials with varying shapes. This approach enables the precise control of mechanical properties other than particle shape, eliminating potential confounding factors. Then, we construct particle flow samples with distinct shape characteristics, quantitatively assessing their shape variations according to their overall regularity (OR). Flume experiments are conducted, with the findings used to calibrate a discrete element numerical model. By integrating the numerical simulations and experimental data, we systematically investigate the flow, impact, and deposition behaviours of granular flows under diverse flume inclinations considering the influence of particle shape. The results demonstrate that the mobility and destructiveness of granular flows increases with higher OR values and steeper flume inclinations. The transition from pile-up to runup deposition is primarily controlled by the flume inclination, while within specific inclination ranges, changes in OR can also induce deposition mechanism transition. This study provides substantial insights into interactions between granular flows and protection structures, emphasizing the significance of particle shape and terrain characteristics within a source area.

The influence of particle shape on crushing pattern and energy dissipation within a pressurized sand damper

A discrete element method (DEM) model was introduced to examine the crushing pattern, energy dissipation, force–displacement curves, and stresses within a pressurized sand damper (PSD). Simulations were carried out with various particle shapes, including elongated, triangle, pyramid, cube, and hexagon. While monitoring the force–displacement curves, it was observed that the hexagon-shaped particles yielded the highest forces, while the triangle-shaped particles resulted in the lowest forces. Altering the particle shapes did not significantly impact the overall shape of the force–displacement curves, suggesting that dynamic force generation remains unaffected by the particle shape. Particle crushing was closely examined for all particle shapes, and it was concluded that all shapes exhibit relatively similar crushing locations and patterns. In the analysis of normal stress, hexagon- and elongated-shaped particles were found to experience the highest and lowest stresses, respectively. Observing the energy dissipation revealed that, among the shapes studied, triangle-shaped particles had the lowest cumulative dissipated energy over five loading-unloading cycles, whereas hexagon-shaped particles had the highest. The calculation of specific damping capacity showed a large loss angle, indicating the presence of large strains inside the model.

Thermal Conductivity of Nanofluids: Influence of Particle Shape

Thermal Conductivity of Nanofluids: Influence of Particle Shape

Influence of particle shape on creep and stress relaxation behaviors of granular materials based on DEM

The creep and stress relaxation behaviors stem from time-dependent changes in the microstructure of granular materials. As a non-negligible inherent granular material characteristic, particle shape plays a significant role on the formation and evolution of microstructure. However, the effects of particle shape on creep and stress relaxation behaviors of granular materials are still open questions. In this study, 3D DEM models based on the rate process theory and superellipsoids are incorporated to simulate the creep and stress relaxation of granular samples with different aspect ratios and blockiness. The results show that the aspect ratio and blockiness of particle have a great effect on creep and stress relaxation. However, the effects of aspect ratio and blockiness on creep and stress relaxation are coupled. Further analysis on contact forces shows the influences of aspect ratio and blockiness on creep mainly come from the contact force ratio. The influences of the aspect ratio and blockiness on stress relaxation mainly arise from the variation of the normal contact force anisotropy of the granular assemblies. The above results provide the tendency and mechanism on the effects of particle shape on creep and stress relaxation of granular assemblies.

Numerical study on influence of particle shape and deformation on friction behavior of flexible cylindrical particle flows

AbstractA discrete element method (DEM) model for deformable particles is established and adopted to investigate the Jenike shear process of flexible cylindrical particles with different aspect ratios (4 < < 6). The DEM model is firstly validated against both experimental data and analytic solutions. Then, numerical simulations are carried out and the effects of particles shape and deformation on their friction behavior are investigated through a particle‐scale analysis on particle deformation, coordinate number, contact forces, orientation and internal friction angle. Comparative results between flexible and rigid particles under the same conditions show that the shear stress increases almost linearly with the normal load regardless of particle stiffness or shape. For both rigid and flexible particles, the shear stress and internal friction angle increase with . The shear stress and internal friction angle of the flexible particles are higher than those of the rigid ones especially when = 6. The latter has more inter‐particle contacts but the former has stronger contact forces. When = 4 and 5, the flexible particles without many initial deformations will deform significantly during the shear process with a complex reconfiguration taking place. However, when = 6, the initial deformation and internal forces of the flexible particles only change slightly during the shear process. It is thus believed that the high shear stress and internal friction angle of the flexible particles with = 6 are caused by their solid packing structure which strongly enhances the capability of the particle flow to resist shear. The current knowledge will be helpful for improving the kinetic theories for granular flow for complex irregular particle flows.