Granular Matter最新文献

Screening units, which are essential machines across industries where improvement studies are needed today, have gained importance efficiency and energy saving. In this study, the screening process of the copper ore pile was analysed using the discrete element method (DEM) employing the geometry and feeding conditions of the mobile screening unit. Using initialanalyses, the effects of screen rotation speed and pile volume for different mass distributions are evaluated to identify the most effective configuration. The effect of hole geometry and mass distribution was examined by modifying the size distribution of the pile. Efficiency and capacity calculations were performed by increasing the pile’s feeding volume with equal mass distribution. In this study, which aims to identify the conditions under which the most efficient and highest-capacity screening operation occurs, improvements were made to the screen design. In addition, the wear analysis was simulated, and the effect of changes in feeding conditions on the screen life was investigated. The results highlighted that the screen design to be used in the screening operation is directly affected by the pile characteristics, demonstrating the significance of DEM-based modelling in industrial screening optimization.

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Moisture content critically influences the matric suction and stress distribution within subgrade soils, directly affecting their load-bearing capacity. Understanding the internal mechanisms by which moisture variations degrade subgrade performance is essential. This study proposes a novel coupled simulation method based on the Volume of Fluid (VOF) theory to fully resolve the relationship between matric suction and stress conditions among the air–water–solid phases in unsaturated subgrades. By coupling Computational Fluid Dynamics (CFD) with the Discrete Element Method (DEM), the proposed approach incorporates phase fraction modeling to capture particle interactions and quantify the drag forces between phases. The results demonstrate that using phase fractions enables effective modeling of matric suction variations at the pore scale. The proposed method accurately captures the intermediate suction range (10⁴–10⁶ kPa), with errors below 2% in low suction scenarios. It provides detailed insights into particle-scale stress redistribution under varying moisture conditions. Furthermore, the numerical simulations of resilient modulus of subgrade soils matches well laboratory measurements, with deviations within 3–5%, confirming the reliability and predictive capability of the proposed numerical approach.

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Understanding the strength and deformation behavior of recompacted loess is essential for the stability assessment of man-made geotechnical structures in loess regions. While numerous studies have examined the macroscopic mechanical properties of unsaturated recompacted loess, the underlying particle-scale micromechanical deformation mechanisms remain inadequately explored. In this study, a series of drained triaxial tests were conducted on unsaturated recompacted loess under varying matric suctions and mean net stresses to investigate their effects on strength and deformation behavior. The experimental results indicate that higher matric suction increases deviatoric stress due to suction-induced apparent cohesion, whose influence weakens with increasing mean net stress. Moreover, all specimens exhibit continuous volumetric contraction during shearing, consistent with the strain-hardening behavior observed in the stress–strain curves. To interpret these observations from a micromechanical perspective, the original Hill contact model within the discrete element method (DEM) framework was modified by incorporating suction-dependent micromechanical parameters. The modified model was calibrated and validated against laboratory data, showing good agreement in reproducing both stress–strain and volumetric deformation behaviors. Further micromechanical analysis reveals that suction enhances capillary bonding at low net stress, but its influence diminishes as the mean net stress increases. Specifically, at low net stress, higher suction results in a greater proportion of tensile (i.e., capillary) contacts and slightly reduced particle displacements, indicating stronger interparticle bonding. As the mean net stress increases, particle displacements become slightly larger and contact stability is primarily governed by vertical contact forces rather than suction effects. These micromechanical insights are consistent with the experimental observations, thereby establishing a clear link between particle-scale interactions and macroscopic mechanical responses.

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Predicting partial coordination numbers and contact proportions among different contact types is essential for developing theoretical models that link local contact characteristics to the macroscopic mechanical behavior of disordered multicomponent packings. The original Dodds model performs well for binary mixtures with small size ratios but has limited applicability to systems with large size ratios (α > 6.46). This study systematically analyzes the range of small-particle area fractions (f_{s}) over which the two-dimensional (2D) Dodds model remains valid for binary mixtures with α > 6.46 under gravity-free packing conditions. The results indicate the model provides reliable predictions when (f_{s}) exceeds the optimal value (f_{s}^{{{text{opt}}}}), which corresponds to the maximum packing density, but exhibits large errors when (f_{s} < f_{s}^{{{text{opt}}}}), where the discrepancies between the theoretical configuration and the actual packing structure become non-negligible. To address this limitation, a two-stage modification of the Dodds model is introduced. First, a portion of non-rattler small particles is distributed, followed by the redistribution of the remaining ones around the initially placed particles to approximate realistic local configurations. The modified contact statistics are then derived under simplified assumptions. Predictions from both the original and modified models are validated against discrete element method simulations for 2D dense binary assemblies with α = 7, 9, 12, and 16, and experimental data for α = 7, 9. The modified model improves predictions for α > 6.46 and (f_{s} < f_{s}^{{{text{opt}}}}), providing a framework for extending structural modeling approaches to multicomponent mixtures with large size ratios and to more complex three-dimensional systems.

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The dispersion of granulated particles in a liquid is an important process that significantly affects the quality, stability, and functionality of industrial products. It is also a phenomenon of interest in fundamental science. Changes in the particle size distribution (PSD) in a suspension of granules are widely used as indicators of the progression of various dispersion behaviors. In this study, we used the time-domain laser diffraction method to observe dispersion in a granular suspension. We then applied principal component analysis (PCA) to analyze the measurement data, which were obtained as a time series, and extract the characteristic changes in particle size during the dispersion. By extracting the principal components from multidimensional data using PCA, we could characterize the dispersion-phase behavior and separate the peak components, which could not be captured by conventional analyses using representative values such as percentiles. In particular, by applying the PCA method—commonly used in spectroscopy—to PSD data, we obtained new insights suggesting the presence of complex dispersion pathways and intermediates. The findings of this study advance our understanding of granule dispersion dynamics and help establish a new framework for analyzing particle dispersion processes, which can assist in particle design, formulation optimization, and extending scientific knowledge in this area.

The hydro-mechanical coupling interaction of the sandstone is an essential scientific issue in geological and geotechnical fields, which always holds the key to understanding the meso-mechanism underlying the water-induced geohazards such as water inrush and piping erosion. In this study, a new fluid–solid coupled numerical method is developed by combining the finite difference method (FDM) with the discrete element method (DEM). The proposed FDM-DEM coupling method not only solves the seepage field through FDM discretization but also dynamically updates the permeability by explicitly capturing fracture initiation and propagation within sandstone. A representative case of hydro-mechanical coupling interaction of the sandstone was used to validate the accuracy of the proposed method. The effects of confining pressure and seepage pressure on the mechanical properties and permeability evolution of sandstone were evaluated by normalizing the test conditions. Moreover, the evolution laws of the fluid velocity field, particle displacement field, and fractures within the sandstone under the hydro-mechanical were discussed. The distribution characteristics of normal and tangential contact forces within the sandstone were studied. All the numerical results were in good agreement with the experimental or analytical results reported in literatures. The results of the study can provide a new insight into the meso-mechanics of complicated fluid–solid interaction in sandstone.

The paper presents the behaviour of samples made of self-manufactured polydimethylsiloxane (PDMS) grains in a photo-elastic confined uniaxial compression test. PDMS particles were produced using the water-based method, resulting in grain shapes that are close to spherical, with diameters ranging from 2.0 to 16.0 mm. The samples tested were of the same size; however, they consisted of grains of different fractions, diameter spans, and aspect ratios relative to the dimensions of the test box. They were subjected to a load-unload cycle according to several scenarios, first to determine the load that induces a measurable photo-elastic effect. To study the potential relationship between the uniaxial strain calculated based on the change in a sample’s height and the corresponding optical parameters, a parallel analysis was conducted using the average image brightness. It led to the proposal of standardised strain and brightness parameters, which reduced the influence of loading scenarios and camera settings on the test results, allowing for the study of the other factors. On this basis, a unique relationship has been found between normalised uniaxial strain and normalised relative average image brightness, encompassing both loading and unloading regimes. In contrast, two calibration curves are required to calculate stress from brightness. The most interesting finding is that, despite the different force network structures observed in the uniaxial compression test, they do not appear to affect the behaviour of the granular samples on a macro-scale.

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The shape of particles is an inherent property that significantly influences the breakage strength of calcareous granular material, but the quantitative relationship between these factors remains unclear. In this study, the shape indicators of calcareous sand particles were calculated using three-dimensional scanning results. Subsequently, uniaxial compression tests were conducted to obtain the breakage strength of calcareous sand, and the influence of shape variations on breakage strength was determined. The results indicate that as the aspect ratio of particles decreases or sphericity increases, the average breakage strength (( sigma _{{text{m}}} )), characteristic breakage strength (( sigma _{{text{0}}} )), and theoretical average breakage strength ((bar{sigma})) of calcareous sand all decrease progressively. Furthermore, the required breakage energy also declines, following a nearly linear trend. Both breakage strength and energy of calcareous sand exhibit a Weibull distribution, with the Weibull modulus (m) for breakage strength ranging between 1 and 2, and for breakage energy ranging between 4.48 and 6.49. These findings provide valuable insights for theoretical research, engineering practice, and numerical simulations.

We present a simple, strongly nonlinear and short inverse tapered granular alignment (radii small to big) that can transform an impulse into a progressively wider and slower moving solitary wave. The system curiously also serves as an impact dispersion system for an impulse initiated at the smallest grain.

Solitary wave expansion in the Inverse Tapered Chain

The abrupt interruption due to the closure of the valve during the gravity-driven drainage of a liquid and granular medium results in the backflow of materials, which is widely encountered during pneumatic conveying. This phenomenon bears a strong resemblance to the classical water hammer effect, which is reported for the first time by the present authors in “Backward flow and jet formation of liquid and granular medium in a gravity drainage system following a sudden valve closure”, Powder Technology, Volume 438 (2024). Under specific conditions, one may encounter jet formation at the free surface. The current article produces a computational investigation on the effect of the rate of contraction on the backflow of materials and jet formation. Detailed parametric research is executed to characterize and compare the phenomenon for both the flowing medium,—liquid, and granular matter with the variation of rate of contraction. The Rayleigh Plateau instability led interesting phenomenon of jet rupture is also articulated in this article during the collapse of the long liquid jet at a lower level of rate of contraction (r (as described in Eq. 18) < 1). The current article addresses the effect weber number (We) on the jet rupture and energy dissipation due to jet rupture during the collapse of it. The present article also introduces the formation of a hollow granular jet at a lower level of r (r = 0.27) due to the introduction of a long reducer between the drainage tube and the extension line and drastic reduction of bulk density of the jet. The investigation is further extended to understand and differentiate the evolution and collapse of hollow and solid jet. The comparison of the energy dissipation during the formation and collapse of both the jets is studied too.

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