Coupling Discrete Element Method Research Articles

Modeling of particle migration in piping based on an improved discrete element method

Pore-scale particle migration in piping is the main reason of the suffusion-induced damage, which poses a significant threat to earth-rock dams. In order to investigate the micro-mechanism of piping seepage process, an improved fluid-solid coupling discrete element method is proposed in this paper. In this method, particles in a packed model are divided into coarse- and fine particle groups. Pores can be defined based on the coordinates of the coarse particles and the Delaunay triangulation algorithm. A pore density flow method is introduced to calculate the overall fluid pressure of each pore and the fluid flow via pore throats. Further, the drag force on fine particles inside a pore can be calculated according to the fluid velocities of the neighboring four pore throats. The proposed method was implemented in the discrete element software MatDEM, and was successfully used to simulate fine particle migration of piping, the particle loss process, and the related variation of permeability coefficient. The pore-jamming phenomenon during the fine particle migration is observed. The model provides an effective way for the numerical analysis and mechanism study of piping seepage process at the pore scale.

Two-scale concurrent simulations for crack propagation using FEM–DEM bridging coupling

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.

GPU-powered CFD-DEM framework for modelling large-scale gas–solid reacting flows (GPU- rCFD-DEM) and an industry application

The coupling of CFD (computational fluid dynamics) and DEM (discrete element method) is extensively used for simulating gas–solid reacting flows in various industrial processes, while its high computational cost limits its industry applications, especially large-scale systems with a large number of particles and complex geometries. This paper reports a robust highly efficient GPU (graphics processing unit) − powered CFD-DEM coupling approach that is, for the first time, capable of simulating large-scale gas–solid reacting flow systems with complex geometries (GPU- rCFD-DEM). The fluid flow calculations are performed using CPU parallelization, while the particle flow simulations leverage GPU parallelization, and the coupling calculations between CFD and DEM are fully implemented on GPU. The model includes advanced coupling strategies to enhance numerical stability, especially when handling complex geometries with unstructured CFD meshes. The developed model is validated through experimental measurements and its computational performance is evaluated by comparison with previous GPU-based simulations. It shows good agreement with the experiments and superior performance compared to the traditional coupling method. The model is then applied to simulate raceway dynamics and coke combustion in an industrial-scale blast furnace, showcasing its effectiveness in handling complex geometries and a huge number of particles in gas–solid reacting flows. This work provides an efficient and robust solution for numerically simulating industrial applications of gas–solid reacting flow systems.

Prediction of adjacent single pile deformation induced by tunnel excavation based on the Pasternak model

The construction of metro tunnels in soft ground would cause significant settlement of the ground surface and deformation of buildings and their foundations in the vicinity of the tunnels. The deformation laws of the pile of the neighbouring structures induced by the tunnel construction have not yet been fully identified. This paper analyzed the impact mechanism of tunnel construction on piles based on the Pasternak model, deduced the calculation methods of additional horizontal displacement and additional internal force of piles, and introduced three solution methods. The computational method results have been validated through numerical simulations using coupling of discrete element method and finite difference method and compared to select laboratory data. The results show that the model accuracy is better when the tunnel axis burial depth is less than the pile bottom burial depth. The analysis shows that the tunnel burial depth significantly influences the displacement distribution of the adjacent single pile, while the impact on the peak displacement is insignificant. The thickness of the elastic layer (C) is inversely related to the maximum horizontal displacement and internal force, but it does not impact the distribution patterns of the displacement and internal force. For thickness of the elastic layer (C), the bending moment’s point is constant at 2 m above and below the tunnel axis, whereas the shear force’s point remains constant at the buried tunnel axis’s depth and 4 m above the tunnel axis.

Numerical modeling of structural body deformation under free surface flow based on volume of fluid–discrete element method coupling

In this work, we proposed a numerical model based on the coupling of the volume of fluid–discrete element method and bond particle method (BPM). The simulation of particle bonding and the structural body formation process had been presented, and the inter-particle bonding mechanism was introduced. We also tested dam-busting impact elastic and wedge plates at high Reynolds numbers (1.26 × 107 and 2.16 × 106) and compared the results with numerical simulations. The results show that the model has mean errors of 3.9% and 6.5% for the large and the micro-deformations, respectively. It is in perfect agreement with the curve trends of the test and keeps good convergence for different particle sizes. In addition, we also used the model used to study the hydrodynamic changes in underwater box net structures in offshore aquaculture, and the deformation kinematic properties of box nets under different material strengths were evaluated. This numerical model of this study provides the effective theoretical support and engineering guidance for the further study of the behavior of structural bodies under hydrodynamic action.

Modelling Binder Degradation in the Thermal Treatment of Spent Lithium-Ion Batteries by Coupling Discrete Element Method and Isoconversional Kinetics

Developing efficient recycling processes with high recycling quotas for the recovery of graphite and other critical raw materials contained in LIBs is essential and prudent. This action holds the potential to substantially diminish the supply risk of raw materials for LIBs and enhance the sustainability of their production. An essential processing step in LIB recycling involves the thermal treatment of black mass to degrade the binder. This step is crucial as it enhances the recycling efficiency in subsequent processes, such as flotation and leaching-based processing. Therefore, this paper introduces a Representative Black Mass Model (RBMM) and develops a computational framework for the simulation of the thermal degradation of polymer-based binders in black mass (BM). The models utilize the discrete element method (DEM) with a coarse-graining (CG) scheme and the isoconversional method to predict binder degradation and the required heat. Thermogravimetric analysis (TGA) of the binder polyvinylidene fluoride (PVDF) is utilized to determine the model parameters. The model simulates a specific thermal treatment case on a laboratory scale and investigates the relationship between the scale factor and heating rate. The findings reveal that, for a particular BM system, a scaling factor of 100 regarding the particle diameter is applicable within a heating rate range of 2 to 22 K/min.

Study on impact mechanical characteristics and screening performance of fine coal during flip-flow screening process

ABSTRACT Screening is a key link in the coal preparation, and flip-flow screening is the important method for achieving efficient classification of fine coal. During screening, the mechanical response of the screen plate caused by materials collisions not only changes its impact mechanical behavior, but also affects the final screening effect. It is urgent to clarify the mechanism of interaction between particle swarm and flip-flow screen plate. Therefore, in this study, based on the coupling of Discrete Element Method and Finite Element Method (DEM-FEM), the impact mechanical characteristics of the screen plate was explored during the collision process between the coal particle swarm and the screen plate. Conduct specific research on collision process, the relationship between the motion position of the screen plate and the distribution of impact stress was clarified. The trend of impact stress changes near the collision point was studied, and the optimized design of the flip-flow plate was carried out. On this basis, the influences of the processing capacity on the distribution of the screening products and screening efficiency were clarified. With an increase in the processing capacity of the flip-flow screen, the distribution coefficients of particles with approximate screen mesh size in the oversize gradually increased, resulting in an increase in distribution size and equal error size. Furthermore, the screening efficiency decreased from 84.91% to 81.36%. The study results provided a theoretical basis for the development of efficient screening technology for fine coal.

Determining Digital Representation and Representative Elementary Volume Size of Broken Rock Mass Using the Discrete Fracture Network–Discrete Element Method Coupling Technique

Obtaining the digital characterization and representative elementary volume (REV) of broken rock masses is an important foundation for simulating their mechanical properties and behavior. In this study, utilizing the broken surrounding rock of the main powerhouse at the Liyang pumped storage power station as an engineering background, a three-dimensional fracture network generation program is first developed based on the theories of discrete fracture network (DFN) and discrete element method (DEM). The program is then integrated with a distinct element modelling platform to generate equivalent rock mass models for broken rock masses based on the DFN–DEM coupling technique. Numerical compression tests are conducted on cylindrical rock specimens produced using the proposed modelling approach, aiming to determining the REV size of the target rock masses at the Liyang power station. A comparative validation is also performed to examine the REV result obtained from the proposed approach, which adopted a REV measuring scale index (RMSI) to determine the REV size. Results indicate that the organic integration of DFN simulation techniques and DEM platforms can effectively construct numerical models for actual broken rock masses, with structural surface distributions statistically similar to the real ones. The results also show that the REV size of the investigated rock masses determined by the cylindrical rock models is 5 m × 10 m, which aligns with the size determined by the cubic rock models, as the target cubes show the same height as the cylindrical specimens. This study provides a model and parameter basis for the numerical calculation of the mechanical behavior of broken rock mass.

Design and Experiment of Adaptive Profiling Header Based on Multi-Body Dynamics–Discrete Element Method Coupling

To promote the germination of rice panicles during the regeneration season, it is necessary to ensure a stubble height of 300–450 mm when mechanically harvesting the first-season rice. However, due to variations in the depth of the paddy soil and fluctuations in the height of the header during harvesting, maintaining the desired stubble height becomes challenging, resulting in a significant impact on the yield during the regeneration season. This study presents the design of an adaptive profiling header capable of adjusting the height and level of the header adaptively. Based on the theoretical analysis of the profiling mechanism, a quadratic regression orthogonal rotation combination experiment is designed. Considering the actual field conditions, the range of each factor is determined, and simulation experiments are conducted based on the MBD-DEM coupling to establish a mathematical regression model between each factor and indicator. In the case of the profiling wheel linkage length of 562 mm, profiling wheel width of 20 mm, and profiling wheel mass of 3.6 kg, the supporting force of the header on the profiling wheel would be greater than zero, the supporting force of soil on the profiling wheel and the depth of soil subsidence represent the smallest values, and the highest sensitivity and accuracy of the profiling wheel are achieved. Bench tests demonstrated that the header exerts a force on the profiling wheel, confirming the normal functioning of the profiling. The average magnitudes of forces exerted by the soil on the profiling wheel are obtained to be 31.98 N, 31.63 N, and 30.86 N, whereas the corresponding average soil subsidence depths are obtained as 3.4 mm, 5.6 mm, and 8.3 mm, aligning closely with the simulation values. The results indicate that the profiling mechanism achieves high accuracy in ground profiling and that the structural design is reasonable. By employing fuzzy PID control to adjust the height of the header, the average error in adjustment is obtained as 6.75 mm, while the average error in the horizontal adjustment is derived as 0.64°. The header adjustment is fast, offering high positioning accuracy, thereby meeting the harvesting requirements of the first season of ratooning rice.

Design and experiment of a shovel-tooth removal end-effector for abnormal plants in hybrid rape breeding based on MBD-DEM coupling.

In view of the problem that removing abnormal plants in breeding rape requires a large amount of labor and is inefficient, combined with the planting requirements of breeding rape, a shovel-tooth end-effector was designed, and a shovel-tooth removal test bench was built. A simulation model based on MBD (Multibody Dynamics)-DEM (Discrete Element Method) coupling was constructed. Then we conducted a Box-Behnken test with four factors and three levels. Taking the angle of soil penetration, speed of soil penetration, depth of soil penetration and speed of shovel-tooth gathering as the test factors, the soil penetration force and shovel-tooth gathering force as the test indicators. The mathematical regression model between test indicators and test factor was established. After optimizing the parameters of the model, the best combination of parameters with low soil penetration force and low shovel-tooth gathering force was obtained: angle of soil penetration of 84°, speed of soil penetration of 9 cm/s, depth of soil penetration of 8cm, and speed of shovel-tooth gathering of 6 cm/s. The simulation model was validated by field experiments. The average soil penetration force and average shovel-tooth gathering force of the three groups of pull-out tests were 34.8 N and 763.0 N, respectively. The removal rates were 96%, 92%, and 94%, all greater than 90%, indicating that the removal effect of the shovel-tooth end-effector was good, and the parameters were reasonably designed. The results can serve as reference for the design of rape abnormal plants removal device and the operation of MBD-DEM coupling simulation end-effector.

Simulation and parameter optimization of high moisture rice drying on combine harvester before threshing

Aiming at the problems of conveying, threshing and cleaning devices blockage while harvesting the high moisture by combine harvester, the idea of reusing waste heat of combine harvester to dry rice on machine before threshing was put forward. The surface moisture of rice dried by hot air in cutting header was studied. The computational fluid dynamics (CFD) coupling discrete element method (DEM) simulation experiment based on the quadratic orthogonal rotating center combination test method was performed. The impact of feeding amount, hot air velocity, hot air temperature and initial water content of rice on the rice dehydrator rate was analyzed and the relationship model between them was built. The optimal solution for the rice drying was obtained using the relationship model. A test bench was set up to validate the accuracy of the model. The results demonstrate that each factor significantly influences the dehydration rate with their important order as follows: rice feeding quantity > rice initial moisture content > hot air temperature > hot air velocity; the optimal solution is rice feed quantity of 100 g, hot air velocity of 6 m/s, hot air temperature of 150 °C, initial moisture content of 20% and a maximum dehydrator rate of 1.541%; the validation test confirms that the acquired relationship model exhibits sufficient prediction accuracy with the maximum relative error of 8.5%.

Force-transmitting of granular medium under ultrasonic vibration: Experiments and simulation

For the lightweight alloy tube which is hard to deform with conventional techniques, Ultrasonic vibration granular medium forming (UGMF) technology was proposed, combining solid granular medium forming with ultrasonic vibration plastic forming technology. To investigate the force-transmitting law of granular medium in the forming process of UGMF, and study the force-transmitting characteristics of granules medium under ultrasonic vibration, achieved the control of pressure distribution in the inner surface of the tube to improve the forming performance of tube. The curve path force-transmitting experiment under ultrasonic vibration was designed, the distribution law of lateral pressure has been obtained, and in combination with Janssen stress distribution Based on the Janssen stress distribution, the expression of the pressure function of the curve path force-transmitting was derived. At the same time, PFC2D and ABAQUS software were used to establish the discrete element method (DEM) model and the finite element method (FEM)-DEM coupling model, the microscopic and macroscopic curve path force-transmitting analysis of the ultrasonic vibration. The influence of ultrasonic vibration on curve path force-transmitting was investigated. The results show that the application of ultrasonic vibration increases the force-transmitting performance of the granules, and the force-transmitting efficiency is twice that of the non-vibration condition. Based on the experimental results, the accuracy of the expression was verified. From the microscopic point of view, it is found that the application of ultrasonic vibration makes the granular force chain thicker and the force-transmitting efficiency increases. From the macroscopic point of view, it is found that with the increase of transverse distance, the highest point of the lateral wall of the curve moves downward.

Stability analysis of tunnel under coal seam goaf: Numerical and physical modeling

The goaf formed by coal seam mining would dramatically reduce the strength and stiffness of the ground in and around the goaf, which is not conducive to tunnel excavation near the mined-out area. By establishing the Finite differential method and Discrete element method coupling numerical analysis method and conducting similar model test, the influence of dip angle, thickness and distance of coal seam goaf on the stability of unsupported tunnel excavation is studied. The results show that when the tunnel under the goaf is excavated, the circumferential stress increment increases first and then decreases along the radial direction of the tunnel, the radial stress increment gradually decreases to zero along the radial direction of the tunnel, the displacement is approximately distributed in a trough shape, and the maximum displacement is at the top of the tunnel. The area of the stress loosening zone (SLZ) is negatively correlated with the dip angle and the distance of the goaf, and positively correlated with the thickness. The SLZ near the goaf is larger, and the peak value of the asymmetry is about 1.35. When the thickness of the mined-out area is 1.8–2.1 m, the SLZ and displacement around the tunnel increase sharply and then become stable. When the dip angle of the mined-out area is greater than 30° or the distance exceeds 1.3 times tunnel diameter (D), the asymmetry converges. The research results of this paper are of great importance to the design and construction of tunnel support and the formulation of excavation schemes.

Modeling Soil–Plant–Machine Dynamics Using Discrete Element Method: A Review

The study of soil–plant–machine interaction (SPMI) examines the system dynamics at the interface of soil, machine, and plant materials, primarily consisting of soil–machine, soil–plant, and plant–machine interactions. A thorough understanding of the mechanisms and behaviors of SPMI systems is of paramount importance to optimal design and operation of high-performance agricultural machinery. The discrete element method (DEM) is a promising numerical method that can simulate dynamic behaviors of particle systems at micro levels of individual particles and at macro levels of bulk material. This paper presents a comprehensive review of the fundamental studies and applications of DEM in SPMI systems, which is of general interest to machinery systems and computational methods communities. Important concepts of DEM including working principles, calibration methods, and implementation are introduced first to help readers gain a basic understanding of the emerging numerical method. The fundamental aspects of DEM modeling including the study of contact model and model parameters are surveyed. An extensive review of the applications of DEM in tillage, seeding, planting, fertilizing, and harvesting operations is presented. Relevant methodologies used and major findings of the literature review are synthesized to serve as references for similar research. The future scope of coupling DEM with other computational methods and virtual rapid prototyping and their applications in agriculture is narrated. Finally, challenges such as computational efficiency and uncertainty in modeling are highlighted. We conclude that DEM is an effective method for simulating soil and plant dynamics in SPMI systems related to the field of agriculture and food production. However, there are still some aspects that need to be examined in the future.

Experiments and simulation of block motion in underwater bench blasting

The blasting mechanism underlying drilling and blasting of underwater rocks, as an important component of the engineering blasting technology, has not been systematically studied. Laboratory model experiments are expensive and take a long time, while field tests fail to obtain timeous breakage and accumulation effects of underwater blasting, and may even be impossible. Considering this, a model experiment of underwater concrete bench blasting was designed, and the motion of blasted blocks was observed and evaluated with a high-speed camera. Then, numerical simulation was conducted based on Fluent and an engineering discrete element method coupling program complied using the application programming interface. Results show that the blocks form a bulge in the underwater blasting experiment under action of blast waves and expansion in the first period of bubble pulsation. Then, some blocks shrink in the first period of bubble pulsation. As the charge increases, the blast load exerts larger disturbance on the block group, resulting in significant motion of blasted blocks along the vertical direction. At the same time, the horizontal displacement of blasted blocks in the throwing direction increases.

A Hybrid PBM-DEM Model of High-Pressure Grinding Rolls Applied to Iron Ore Pellet Feed Pressing

Mathematical models of high-pressure grinding rolls (HPGR) have attracted great attention, owing to their role in optimization of operating machines as well as in the design and selection of new ones. Although population balance models (PBM) and the discrete element method (DEM) have been used in this task, both suffer from important limitations. Whereas PBMs have challenges associated to the prediction of operating gap and to the validity of several of its assumptions in different formulations in the literature, application of DEM has its own challenges, in particular when fed with distributions containing large amounts of fines. This work proposes a hybrid approach in which the coupling of DEM to particle replacement models and multibody dynamics is used to predict operating gap, throughput and power, as well as providing information along the rolls length that is used in PBM to predict the product fineness. The hybrid approach is then compared to both DEM and a PBM (Modified Torres and Casali), demonstrating similar results to the later when applied to simulating a pilot-scale machine operating under different conditions, but improved prediction when applied in scale-up to an industrial-scale HPGR.

A review of recent development for the CFD-DEM investigations of non-spherical particles

The coupling between fluid and granular materials is commonly encountered in nature and engineering practice. Moreover, the shape of granular materials in practical applications is normally non-spherical. Therefore, investigating the particle-fluid systems containing non-spherical particles for a deeper understanding of their underlying mechanisms and then for improving the performance of the related industrial processes should be an urgent necessity for practical needs. For investigating the intricate flow behaviors of particle-fluid systems, the numerical simulation method of coupling DEM (Discrete Element Method) with CFD (Computational Fluid Dynamics) has been widely recognized as a promising tool, and many efforts have been devoted to the CFD-DEM investigations of non-spherical particles in recent years. This paper aims to review development of the CFD-DEM investigations for non-spherical particles from theoretical models to applications in recent six years. It primarily represents three principal aspects: the theoretical foundations of DEM for modeling non-spherical particles, the coupling methodologies between CFD and DEM and the use of the non-spherical CFD-DEM coupling model in different applications involving particle-fluid flows. In the end, the conclusions and the outlooks for future investigations are given.

Development of DEM-MBD coupling model for draft force prediction of agricultural tractor with plowing depth

During agricultural tillage, draft force is the most important factor affecting the performance of soil-machine system. In this study, a full-scale soil-tool-machine coupling model based on the coupling of DEM (discrete element method) and MBD (multibody dynamics) was established to predict draft force according to tillage depth during tillage operation. First, plowing field test was performed through a field load measurement system to develop DEM-MBD coupling model for the draft force prediction according to the tillage depth during the calibration and validation process of the DEM-MBD coupling model. The DEM soil bed was modeled by considering the target tillage depth and reflecting the soil property distribution that changes according to the soil depth. For the soil model, particle mass and surface energy were calibrated using bulk density values measured in the field and shear vane test results. In addition, the weight distribution ratio of each wheel in static state was measured, and the center of gravity was calculated for MBD modeling of the tractor-implement system. Additionally, calibration of tire parameters was performed using the travel speed results of field tests. As a result of the DEM-MBD coupled simulation, the prediction accuracy of travel speed and draft force were 93.2% (86.6%–99.4) and 90.8% (86.4%–99.3%), respectively, depending on the tillage depth. In addition, the prediction accuracy of the draft force was 11–32% higher than the 67.4–70.6% using the ASABE standard D497.4 method. This study is considered to be able to gradually replace the existing field tests with digital twin-based simulation tests. This can provide valuable insights for optimal design while minimizing the development time and cost of soil-machine systems.

Multi-scale modeling of the concrete SHPB test based on DEM-FDM coupling method

The split Hopkinson pressure bar (SHPB) test is the most commonly used method for testing the dynamic mechanical behavior of materials at high strain rates. In this paper, for the SHPB test of concrete, an efficient multi-scale mechanical calculation method based on coupling of discrete element method (DEM) and finite difference method (FDM) is proposed, and SHPB test system for analysis of the macroscopic and microscopic dynamic mechanical properties and damage evolution of concrete under impact loading is established by this coupling method. A three-phase mesoscopic scale model of concrete is constructed by DEM, and the crushability, real geometry-shape, and particle size distribution of aggregates are considered by combining 3D scanning technology and the “ball-clump-cluster” method. Meanwhile, FDM is adopted to simulate the SHPB model, and the “coupling wall” mechanism is applied to realize the signal transmission between the models. On this basis, the stress waves obtained by the direct monitoring method through numerical simulation are basically consistent with those obtained by the theoretical calculation method, which verifies the dynamic characteristics of the SHPB model. Finally, the different types of microcrack propagation are analyzed in the premise of examining the static and dynamic mechanical response of the concrete model. It was found that the distribution of mortar and aggregate microcracks on the outside of the concrete was significantly more than that on the inside due to transverse inertia force, and the superiority of the method in simulating the damage evolution behavior of concrete meso-structural is demonstrated.

A partitioned material point method and discrete element method coupling scheme

Mass-movement hazards involving fast and large soil deformation often include huge rocks or other significant obstacles increasing tremendously the risks for humans and infrastructures. Therefore, numerical investigations of such disasters are in high economic demand for prediction as well as for the design of countermeasures. Unfortunately, classical numerical approaches are not suitable for such challenging multiphysics problems. For this reason, in this work we explore the combination of the Material Point Method, able to simulate elasto-plastic continuum materials and the Discrete Element Method to accurately calculate the contact forces, in a coupled formulation. We propose a partitioned MPM-DEM coupling scheme, thus the solvers involved are treated as black-box solvers, whereas the communication of the involved sub-systems is shifted to the shared interface. This approach allows to freely choose the best suited solver for each model and to combine the advantages of both physics in a generalized manner. The examples validate the novel coupling scheme and show its applicability for the simulation of large strain flow events interacting with obstacles.