Computational Particle Mechanics最新文献

Mactra veneriformis represents the dominant species in China’s mudflat aquaculture. The discrete element model of M. veneriformis and its contact parameters serve as an important basis for the optimization design and simulation study of aquaculture and processing equipment. The contact parameters of the discrete element model of M. veneriformis were measured and calibrated by a combination of experimental testing and simulation calibration. The study measured the range of collision recovery, static, and rolling friction coefficients between M. veneriformis and stainless steel. The Plackett–Burman multifactorial significance screening test was then conducted for the split-cylinder method, the rotate-cylinder method, and the single-cylinder method particle characterization test methods. The ANOVA results were utilized to calibrate the contact parameters. The collision recovery coefficient of 0.29 between M. veneriformis–M. veneriformis and 0.28 between M. veneriformis–stainless steel. The coefficient of static friction of 0.41 was determined between M. veneriformis–M. veneriformis, a coefficient of static friction of 0.62 between M. veneriformis–stainless steel, and a coefficient of rolling friction of 0.23 between M. veneriformis–M. veneriformis and a coefficient of rolling friction of 0.16 between M. veneriformis–stainless steel. After calibration, simulation tests were conducted using the side plate lifting method to verify the contact parameters of the discrete elements of M. veneriformis. The results showed that the simulation angle of repose of the calibrated M. veneriformis had an error of 4% concerning the true angle, thus verifying the contact parameters of the M. veneriformis. The findings of this study can serve as a valuable reference for future research on the optimal design and simulation of the sowing, harvesting, and processing equipment of M. veneriformis. The research methodology employed can provide novel insights for research on discrete elemental parameter calibration of agricultural materials, which has not been extensively studied.

We utilized the discrete element method to simulate the packing of a powder layer by blade spread. Our study revealed the following findings: (1) We uncovered a hereditary relationship that exists between the pouring heap and the packing layer, which plays a significant role in the non-uniform distribution of powder in the packing layer in terms of sizes and shapes. (2) We systematically analysed the influence of sliding speed on powder packing and recommended a threshold sliding rate of 0.15 m/s for achieving a high packing quality. (3) Contrary to the conventional belief that non-spherical powders tend to reduce packing density, our study discovered that the inclusion of a small portion of non-spherical powders can create pathways for efficient gap-filling, resulting in denser packings. (4) By adjusting inter-powder interactions, we observed a transition from discrete powder packing to cluster deposition. (5) We proposed and demonstrated the efficacy of a two-step spreading technique followed by multiple shaking cycles in achieving maximum random packing density. Overall, our work provides a comprehensive understanding of mechanisms involved in the powder spreading process through blade sliding, which may lead to enhanced powder packing density and uniformity and ultimately improved outcomes in additive manufacturing.

In this study, an improved sandwich conveying numerical simulation model was used to analyse the influence of five factors on the conveying efficiency of a vertical sandwich belt conveyor. The mass flow rate of the model was verified using a test model. The results showed that the mass flow rate and shear depth increased as the belt speed increased. Additionally, the particle velocity tends to decrease with increase in depth, and increasing the pressing force increased the contact force chain. Furthermore, the contact force chain remained constant in the vertical direction. The strength of the contact force chain was maximised when the moisture content was 20–30%.

Preexisting fissures are common in rock mass engineering, and these preexisting fissures can considerably reduce the strength of rock masses and the stability of rock mass engineering. Considering that the preexisting fissures are not straight, a DEM numerical simulation model with rough joints under uniaxial compressive loading was constructed. From the analysis of the numerical simulation results, we found that the peak strength increases with increasing inclination angle. Moreover, the JRC influences the peak strength. Even though the JRC values are close, there are still some differences. Moreover, the number of cracks increased slowly before the uniaxial stress reached the peak strength; however, the number of cracks increased remarkably at the postpeak stage. Moreover, the crack path becomes simpler with increasing JRC. The numerical simulation results can provide a numerical basis for rock masses with rough joints in engineering practice.

The improvement of soil behaviour by the bacterial precipitation of calcium carbonate has been extensively studied in geotechnical engineering. However, the evolution of bio-cementation bonds under shear conditions is only partially understood. This research presents a micromechanical approach to gain a deeper insight into the interaction between bio-cemented particles. A series of glass bead samples were treated with Microbial Induced Calcite Precipitation (MICP) and then subjected to direct shear tests. A calibrated model based on the Discrete Element Method was used to reproduce the macro-mechanical paths observed in the experiments, allowing the detailed analysis and description of the bond evolution at the microscopic scale in the treated samples. In general, it was found that a higher rate of bond breakage occurred before the peak shear strength was reached, and this was followed by a relatively constant rate of bond breakage associated with a macroscopic softening trend. Tensile stress was identified as the primary fracture mechanism. Finally, it was determined that the bond breakage mechanism is influenced by several factors, such as bond distribution, particle array, and the mechanical parameters of the bond.

The Discrete element method (DEM) is a robust numerical tool for simulating crack propagation and wear in granular materials. However, the computational cost associated with DEM hinders its applicability to large domains. To address this limitation, we employ DEM to model regions experiencing crack propagation and wear, and utilize the finite element method (FEM) to model regions experiencing small deformation, thus reducing the computational burden. The two domains are linked using a FEM–DEM coupling, which considers an overlapping region where the deformation of the two domains is reconciled. We employ a “strong coupling” formulation, in which each DEM particle in the overlapping region is constrained to an equivalent position obtained by nodal interpolation in the finite element. While the coupling method has been proved capable of handling propagation of small-amplitude waves between domains, we examine in this paper its accuracy to efficiently model for material failure events. We investigate two cases of material failure in the DEM region: the first one involves mode I crack propagation, and the second one focuses on rough surfaces’ shearing leading to debris creation. For each, we consider several DEM domain sizes, representing different distances between the coupling region and the DEM undergoing inelasticity and fracture. The accuracy of the coupling approach is evaluated by comparing it with a pure DEM simulation, and the results demonstrate its effectiveness in accurately capturing the behavior of the pure DEM, regardless of the placement of the coupling region.

Sudden expansion pipes are crucial in fluid dynamics for studying flow behavior, turbulence, and pressure distribution in various systems. This study focuses on investigating the behavior of a two-phase flow, specifically a gas–solid turbulent flow, in a sudden expansion. The Eulerian–Eulerian approach is employed to model the flow characteristics. The Eulerian–Eulerian approach treats both phases (gas and solid) as separate continua, and their interactions are described using conservation equations for mass, momentum, and energy. The study aims to understand the complex phenomena occurring in the flow, such as particle dispersion, turbulence modulation, and pressure drop. The governing equations are solved using house developed code called FORTRAN, a widely used programming language in scientific and engineering simulations. The results of this study will provide valuable insights into the behavior of gas–solid two-phase flows in sudden expansions, which have important applications in various industries, including chemical engineering, energy systems, and environmental engineering. A parametric study of the impact of particles diameters (20, 120, 220, 500 µm), the solid volume loading ratios ((0.005, 0.008, 0.01)) and area ratios (2.25, 5.76, 9) effect of sudden expansion on the streamlines, local skin friction, pressure, velocity, turbulent kinetic energy, and separation zone.