Computational Particle Mechanics最新文献

The relative density is a key indicator of the mechanical properties of coarse-grained soil. To better explain the shear behaviors such as dilatancy–contractancy and softening–hardening in simulations based on Discrete Element Method (DEM), the definitions of the maximum void ratio, minimum void ratio, and relative density were generalized to consider the impact of the confining pressure during the shear process. Comprehensive tests were conducted based on direct shear tests through the DEM. Preparation methods were presented to obtain specimens with the maximum void ratio, minimum void ratio, and target relative density. The direct shear tests show that the shear behavior of coarse-grained soil significantly varies with changes in relative density. Specifically, under high relative density conditions, soils tend to exhibit dilatancy behavior accompanied by softening characteristics. Conversely, under low relative density conditions, soils are more prone to contractancy and display hardening behavior. The peak shear strength increases with increasing relative density, indicating enhanced resistance to deformation. Additionally, compared with the void ratio, the relative density provides a more accurate description of the variation of shear strength parameters with the degree of compactness. These findings suggest that the interactions between soil particles, influenced by confining pressure and relative density, play a crucial role in determining the macroscopic shear behavior of these materials. This study provides a theoretical basis for density control and strength evaluation of coarse-grained soil.

Owing to the narrow diameter of the riserless lifting pipeline, the large size and irregular shape of the particles being transported, and the significant concentration of cuttings present, the formation of a cuttings bed within the pipeline is highly probable, which seriously affects the operational safety of the lifting pump. Understanding the cuttings erosion mechanism of lifting pipelines has become an important research topic. To investigate the influence of various parameters on the erosion mechanism of pipeline cuttings bed, the erosion process was simulated using the computational fluid dynamics–discrete element method. The effects of the initial cuttings bed thickness, drilling fluid inlet velocity, pipe inclination, and drilling fluid viscosity on the erosion rate of the cuttings bed were analyzed. The simulation results showed that the flow rate of the drilling fluid had a significant impact on the erosion rate of the cuttings bed and that the rheology of the drilling fluid changed the erosion form of the cuttings bed. A relationship model of the cuttings erosion rate was established using machine learning, and the calculation results of the model were in good agreement with literature data. These findings provide a theoretical foundation for the hydraulic design of riserless drilling–lifting pipelines and hole-cleaning processes.

The mechanical behavior of the granular materials is significantly affected by debris shape caused by particle breakage. In order to reveal this mechanism, the discrete element method is employed to investigate the effect of debris shape on particle mechanical behavior under different confining pressure. A breakable particle model with realistic external shapes but different debris shapes is constructed, and a series of drained triaxial tests are conducted under varying confining pressures. The macroscopic characteristics of the particles, including the degree of particle breakage, shear strength, and deformation properties, were evaluated. Additionally, the microscopic origins of peak and critical shear strength, as well as deformation characteristics, are discussed from the perspectives of fabric anisotropy and particle motion. Regarding anisotropy, the strength differences between different debris shapes at the peak state are mainly reflected in a_c, a_n, and 1.5a_t. The differences are magnified in the critical state, primarily due to the increasing disparity between a_n and 1.5a_t. Regarding particle motion, as the confining pressure increased, the average displacement of particles decreased. This phenomenon primarily is driven by the decrease in the number of sliding particles, while particle rotation also contributed to some extent to the reduction in displacement. Furthermore, particle motion exhibits a strong correlation with the deformation mechanisms in granular materials. Smaller average displacements lead to shrinkage behavior in the particle assembly, whereas larger displacements result in dilative behavior.

This paper presents an in-depth study of heat transfer in fluidized beds, employing the CFD-DEM technique. The primary focus is to examine the impacts of inlet gas velocity, fluidization regime, and particle size on the thermal behavior of fluidized beds. The results revealed that thermal convection predominantly governs heat transfer in fluidized beds, accounting for the largest fraction of the overall heat transfer process. Particle–fluid–particle thermal conduction was found to contribute approximately 10–20% of the heat transfer, whereas particle–particle conduction exhibits a minor role. Upon increasing the inlet gas velocity, the convection rate intensifies, whereas the particle–fluid–particle conduction rate decreases. Furthermore, the study highlights the differences in temperature distribution between turbulent and bubbling fluidized beds. Turbulent bed demonstrated a more uniform and homogenous particle temperature compared to bubbling. At similar fluidization numbers in bubbling beds, increasing particle diameter enhances thermal convection while reducing particle–fluid–particle conduction. In contrast, the turbulent regime shows minimal differences in heat transfer mechanisms when particle size varies. Additionally, smaller particles are found to significantly improve temperature uniformity in fluidized beds. A comprehensive comparison of simulation results with experimental data validates the accuracy of the employed model, reinforcing its ability to predict heat transfer in fluidized beds reliably. This research provides valuable insights into the complex interplay of various mechanisms of heat transfer within fluidized beds, enabling engineers and researchers to optimize bed performance and enhance temperature control in various industrial applications.

A novel hybrid method for modeling the deformation of granular media in conjunction with the fluid flow has been presented in the current study. While the fluid is simulated through a full-scale Lagrangian framework (Incompressible Smoothed Particle Hydrodynamics), the granular counterpart is modeled through an Eulerian approach (Multilayered Shallow Water Equations). Rapid fluctuation of free surface and velocity are well captured by the full-scale fluid module, whereas various critical stages of granular flow (such as flow initiation and stopping) are reproduced through a layered form of (mu (I)) rheology. The two subsystems are coupled through the drag and the fluid stress tensor by an efficient interphase information transfer. The capability of the coupled formulation is tested for varying configurations of initial conditions and material properties, such as dam-break-induced erosion, subaerial landslide-induced tsunamis, and slow granular column collapse experiments in a reservoir. The proposed framework offers a frugal alternative to the existing full-scale coupled/mixture models with reasonably accurate results.

This research numerically investigates the deposition of airborne particles in a microchannel with elastic ribbons under the influence of thermophoretic forces. The finite element method and an arbitrary Lagrangian–Eulerian (ALE) formulation were employed to solve the governing equations for fluid flow, heat transfer, and particle trajectories. Simulations were conducted for various ribbon configurations and particle sizes ranging from 0.1 to 1.0 µm. Results indicate that thermophoretic forces significantly influence particle deposition in this microchannel system. Increasing the temperature difference between the channel walls, particularly by selecting the upper wall as the hot wall, enhances the thermophoretic force and leads to higher deposition rates. The presence and vibration of elastic ribbons further impact particle trajectories, particularly when placed on the upper wall. In this configuration, the combined effect of thermophoretic force and ribbon movement directs particles toward the lower wall, increasing the likelihood of deposition. Additionally, particles with a diameter of 0.1 μm are more susceptible to thermophoretic forces, resulting in higher deposition rates compared to larger particles. This study provides insights into the complex interplay between fluid flow, heat transfer, and particle transport in microchannel systems with elastic ribbons. The findings have potential applications in various fields, including microfluidic devices, air filtration, and thermal management.

Rainfall-induced landslides are critical geohazards that jeopardise infrastructure and human safety, emphasising the need for precise predictive models to enable effective management and mitigation strategies. This study introduces a GIS-enabled, multi-phase numerical framework that integrates smoothed particle hydrodynamics (SPH) for modelling landslide initiation and the finite difference method (FDM) for analysing post-failure mass flow dynamics. The SPH-based landslide initiation model (LIM) simulates rainfall infiltration and transient seepage effects on slope stability to identify potential failure zones. Subsequently, the FDM-based landslide propagation model (LPM) evaluates the kinematic behaviour of the failed material, providing detailed insights into post-failure mechanics. The framework was validated using benchmark scenarios to confirm its accuracy and robustness. It was then applied to a case study near a hydropower structure, where cumulative rainfall of 282 mm over six days resulted in significant deformation in approximately 7% of the 0.35 km² study area. Depth of failure analysis estimated a release volume of 1.35 (times ) 10⁴ m³, with the displaced mass reaching a maximum height of 10.6 m and a peak velocity of 30.1 m/s in narrow gullies. This integrated framework significantly advances the understanding of landslide processes in complex terrains and offers a computationally efficient tool for hazard assessment and infrastructure resilience planning. Future research should prioritise incorporating obstacle–flow interactions within the framework to optimise the design of protective measures and enhance disaster mitigation strategies.

With rapid advancements in civil engineering, reinforced concrete (RC) structures are extensively used in large infrastructure projects, such as sea-crossing bridges, port terminals, tunnels, and dams. However, exposure to seawater makes these structures highly susceptible to corrosion, accelerating deterioration and reducing their service life. This study investigates concrete cracking induced by non-uniform rebar corrosion through experimental tests and mesoscale peridynamic (PD) modeling. Two sets of accelerated corrosion tests were conducted, and a novel method for generating the heterogeneous mesoscale bond-based PD model was developed, utilizing meshless discretization directly. The model incorporates a time-dependent, non-uniform corrosion approach with a semi-elliptical distribution to represent the evolution and uneven expansion of corrosion products. The numerical method was validated against experimental data, showing strong agreement. The parametric study reveals that thicker concrete covers delay crack initiation, leads to longer and widely distributed cracks, and increase expansion pressure, while larger rebar diameters result in wider cracks and smaller expansion pressure. The shape of the aggregates has minimal impact on crack propagation. Additionally, the presence of multiple rebars accelerates the cracking process, potentially leading to concrete cover spalling. These findings enhance the understanding of corrosion-induced cracking in RC structures and offer valuable insights for improving structural durability and maintenance strategies.

This article reports the in-depth analysis, software simulation, and experimental validation of the negative effects of roller compaction on the electrodes of double-layer capacitors, including particle detachment and current collector elongation. The main component of the coatings of double-layer capacitors is porous-particle-type activated carbon containing agglomerates. This study analyzed the interactions between activated carbon particles and agglomerates and constructed electrode models comprising particles of various shapes based on the results of the aforementioned analyses. A bonded particle model implemented in the discrete element method simulation software was employed to simulate and analyze the vertical pressing and bidirectional movements of the particles. Additionally, the simulation results were validated through roller compaction experiments on the electrodes of double-layer capacitors. The results of the simulations and experiments indicated that the roller compaction of double-layer-capacitor electrodes improved their performance and lifespan but lead to various issues such as particle detachment, current collector elongation, and electrode-thickness rebound. Roller compaction degree, compaction speed, and particle shape were found to be the major factors affecting the outcome of calendering. A greater degree of compaction resulted in greater particle detachment, and increased irregularity of particle shapes had a considerable negative impact on electrodes, which can be alleviated by appropriately increasing the compaction speed.

The extraction of coal resources can greatly affect surface ecology. This impact is particularly seen in loess gully regions (LGRs), where surface cracks form and expand, threatening land stability and ecological safety. To tackle these concerns, this study combines discrete physical simulation experiments with numerical simulations. It focuses on the 135,201 working face of a typical coal mine in the LGR. A 1:100 discrete physical model is created to simulate surface crack generation and expansion across different mining stages. This model enables the analysis of overburden fissure evolution, surface crack development, and surface movement patterns. The research reveals that the development of surface cracks is jointly influenced by the characteristics of mining—induced overburden pressure and the surface topography. During the second mining stage (the Bottom of the Gully Mining Stage), underground mining has a relatively small impact on the surface. However, in the third stage (the Back of the Gully Mining Stage), the surface is more frequently and severely affected by underground excavation, with the same underground mining distance causing more intense surface disturbance. Numerical simulations are also used to study the failure, stress, and surface movement and deformation of the overlying rock layer in the mining area. Field observations further analyse the initiation, active, and recession stages of surface subsidence in the LGR during coal mining. Calculations of tilt and curvature variations between adjacent measurement points show that surface tilt and curvature changes along the inclination observation line are more regular, with maximum tilt values reaching 61.7 mm/m and 60.8 mm/m. However, variations along the strike observation line are influenced by the complex local topography and geomorphology. Overall, the results offer useful insights for coal mining and surface protection in similar geological settings, especially through the physical model experiments applied in this study.