DEM Approach Research Articles

Reverse Engineering to Design an Ergonomic Bio Briquette Packaging Machine

Briquettes are solids that are produced through the process of compression and pressure applicationand if burned will produce a small amount of smoke. Briquette production is carried out using ahammer mill where the raw material for briquettes is charcoal which is then crushed into charcoalgranules. The packaging process is still done manually using a shovel to fill the 50kg sack and thentake it to the sewing machine. The worker's posture when using a shovel has a Rapid Entire BodyAssessment (REBA) score of 12 so it has a high work risk of musculoskeletal disorders (MSDs) andrequires immediate improvement. The working environment at the company produces pollutants,meaning that there is no capture container for the fall of charcoal grains from the hammer mill. Basedon the existing problems, a redesign of the existing machine is needed. The proposed machine wasdesigned using the Reverse Engineering method because the existing condition already uses themachine then the existing machine is decomposed to find out the components and functions of theexisting machine to find alternative concepts. The ergonomic approach uses REBA and LBA todetermine changes in worker posture and the forces acting in the human spine. The DEM approachwas chosen to find out if the charcoal grains dropped from the hammer mill were successfully capturedand to find out the flow of the charcoal grains. The results of the proposed machine design have agood impact on workers in the packaging process.

CFD–DEM modeling of particle segregation behavior in a simulated flash smelting furnace

Particle behavior plays a crucial role in flash smelting furnaces, but limited understanding is hindering further development of this modern pyrometallurgical process. This study presents a two-way coupled CFD–DEM approach to investigate particle distribution, collision, and segregation behaviors within a furnace. The simulation results are validated against experimental data, demonstrating good agreement. The effects of the particle mass–flow rate and size distribution are then analyzed. The results indicate that small particles are carried by airflows to the center of the particle-dense region, whereas large particles remain at the outer part, worsening segregation. Increasing the mass–flow rate significantly increases the particle number density and number of particle collisions but barely influences size-induced segregation. In contrast, enlarging the size of fed particles reduces particle number density and broadens dense distribution within a safe range. This ensures the necessary space and high mixing index of the particles, which benefits high-rate smelting processes.

Advances in granular flow modeling: GPU-based multi-sphere DEM approach and tumbling mill dynamics

Modeling irregular-shaped particulate flow systems poses challenges, especially in mineral processing where accurate representation of particle shape is crucial for capturing macroscopic behavior. The multi-sphere approach, employing DEM, addresses this by approximating particles as overlapping spheres within GPU computing. This study validates particle flow dynamics using literature-based data, showcasing the model’s fidelity and GPU advantages. However, calibration and shape approximation limitations require careful consideration. A quaternion-based orientation method enhances DEM and validates experimental data from packing, hoppers, and tumbling mills. Simulations reveal how particle shape influences granular dynamics, affecting lift-off tendencies, responses to lifter face angles, and power draw trends with mill speed changes. Cubical and spherical particles exhibit orderly packing behavior, contrasting with irregular shapes. This investigation underscores the significant role of particle shape in granular dynamics and its implications for industrial processes.

Deformation and strength degradation mechanism of weathered mudstone soil during dry-wet process based on a developed DEM approach

The soils suffer dry-wet cycles in nature and engineering due to the change of temperature, rainfall and the fluctuation of the groundwater level. The shrinkage-swelling deformation and mechanical properties evolve with the variations of moisture content during a dry-wet process was investigated by laboratory dry-wet cycle tests of a weathered mudstone soil. A DEM approach was developed for simulating the mechanical behaviors during the dry-wet process of the studied soil, considering the shrinkage-swelling deformation by adjusting the shrinkage or swelling ratio of the clay aggregate particles. The irreversible shrinkage-swelling deformation mechanism and the strength degradation mechanism were revealed. The results showed the developed DEM simulations can represent the deformation and the mechanical properties of soils during the dry-wet process. The shrinkage rate of soil decreases with the moisture content from saturation value to 5%, due to the reduction of the shrinkage potence of the clay aggregates. The irreversible shrinkage deformation of soils during a dry-wet process is because the limit swell potence of clay aggregate particles during the wetting process, leading to the swell during the wetting less than the shrinkage during the drying process. The strength degradation was divided into reversible portion mainly affect by the moisture content, and the irreversible portion affected by the meso-crack evolution during the dry-wet process. The large increase of meso-crack number during the drying leads to the rapid reduction of irreversible soil strength, while the decrease of porosity leads the increase of particle contacts and healing of the irreversible soil strength.

Four-way CFD-DEM coupling to simulate concrete pipe flow: Mechanism of formation of lubrication layer

This study introduced a four-way CFD-DEM coupling approach to simulate the shear-induced particle migration (SIPM) mechanism leading to formation of the lubrication layer (LL) during concrete pumping. The CFD-DEM simulations considered the coupled effect of concentration (10 %–40 %) and wide size distribution (1–17 mm) of aggregate and rheology of the mortar for forces between the suspending matrix and the particles (and vice versa), as well as force transmission directly between particles (and the pipe wall). The formation of the LL was successfully simulated through a more realistic understanding the SIPM mechanism and rheological evaluation across the pipe with comparable calculation times compared to the one-way coupled DEM approach, especially for high concentrations. The simulated LL thicknesses of 0.8–2.7 mm compared well with experimental values. The flow rate and rheological heterogeneity of pumped concrete, and rheology of the LL, were found mostly controlled by the granular-skeleton characteristics rather than the suspending-matrix rheology.

Particle flow characteristics in a gas–solid fluidized bed: a microscopic perspective by coupled CFD–DEM approach

Particle flow characteristics in a gas–solid fluidized bed: a microscopic perspective by coupled CFD–DEM approach

Saturation ratio influence on perforation and penetration of concrete subjected to missile impact: a DEM approach

Saturation ratio influence on perforation and penetration of concrete subjected to missile impact: a DEM approach

Numerical Investigation of Recommended Operating Parameters Considering Movement of Polymetallic Nodule Particles during Hydraulic Lifting of Deep-Sea Mining Pipeline

Previously conducted studies have established that pipeline hydraulic transport systems are currently the most promising deep-sea mining systems, and the pipeline transport performance of polymetallic nodules is one of the technical priorities. In this paper, a coupled CFD–DEM approach is adopted to numerically calculate the solid–liquid two-phase flow of seawater with polymetallic nodules. Small-scale experiments were conducted to validate the coupled model. Particle dynamics analysis was carried out under different inlet flow rates, feed concentrations and nodule fragmentation levels. The simulation results show that different operating parameters have significant effects on the pipeline transportation process. With low inlet flow rate, high feed concentration, and high percentage of large particles, the particle distribution and motion characteristics show a trend that is not conducive to safe transport. A set of recommended operating parameters for hydraulic transport of polymetallic nodule pipelines was summarized.

FEM–DEM modeling of pseudo static experiments on scaled‐down rockfill dams with dry stone pitching

AbstractRockfill dams with stone pitching are specific hydraulic structures generally built in the early XXth century where stones used to be hand‐placed without mortar to constitute the upward and downward dam faces. Few studies have been carried out to quantify the specific and critical role of the pitching in the dam stability against both static and seismic forces.Herein, a numerical model is proposed to model pseudo‐static tests performed on four different scaled‐down rockfill dams with a stone pitching. A mixed FEM–DEM approach is used, and two different constitutive models were considered for the backfill. A validation of the numerical model is first proposed based on the scaled‐down tests. Then, the stone pitching displacement profiles and the dams safety factors against failure are analyzed and compared for the four studied cases. This study allows qualitative conclusions to be drawn and pave the way to upcoming investigations on actual structures of the same kind.

Numerical Modeling of Cone Penetration Test: An LBM–DEM Approach

Numerical Modeling of Cone Penetration Test: An LBM–DEM Approach

Multiscale modeling of seepage-induced suffusion and slope failure using a coupled FEM–DEM approach

Suffusion refers to the detachment and migration of fine particles through voids among coarse particles and is one of the major causes of slope failure. This study investigates the seepage-induced suffusion and slope instability using a hierarchical multiscale finite–discrete element method (FEM–DEM). An erosion law with the critical hydraulic gradient for the onset of suffusion is proposed. Two examples, including one-dimensional suffusion and biaxial compression tests, are performed to verify the proposed scheme. Emphases are placed on reproducing suffusion and progressive slope failure process under seepage flow. The results indicate that a shear band is initiated from the slope toe and gradually extends to the crest. The increase of erosion rate accelerates the process of suffusion and slope failure, whereas a higher critical hydraulic gradient plays an opposite role. In addition, fines loss caused by suffusion occurs mainly on the slope surface, especially near the slope toe. Microscopic analyses on locally embedded representative volume elements (RVEs) indicate that RVEs inside the shear band experience severe deformation and microstructural changes, manifested by the rearrangement of soil skeletons and variation of contact force chains.

Numerical simulation study on particle breakage behavior of granular materials in confined compression tests

In order to study the fragmentation law, the confined compression experiment of granular assemblies has been conducted to explore the particle breakage characteristic by DEM approach in this work. It is shown that contact and contact force during the loading process gradually transform from anisotropy to isotropy. Meanwhile, two particle failure modes caused by different contact force states are analyzed, which are single-through-crack failure and multi-short-crack failure. Considering the vertical distribution of the number of cracks and the four characteristic stress distributions (the stress related to the maximum contact force, the major principal stress, the deviatoric stress and the mean stress), it is pointed out that the stress based on the maximum contact force and the major principal stress can reflect the distribution of cracks accurately. In addition, the size effect of particle crushing indicates that small size particles are prone to break. The lateral pressure coefficient of four size particles during the loading process is analyzed to explain the reason for the size effect of particle breakage.

A hybrid workflow for investigating wide DEM parameter spaces

Calibration of contact parameters for the DEM approach remains one of the critical obstacles for an accurate description of powder flows. Ideally, such a calibration approach relies on various macroscopic responses to identify an acceptable set of contact parameters. A significant challenge arises since the parameter space for models contains at least 10 degrees of freedom. The delicate task is to develop a framework that addresses the above-mentioned problems. In this paper, a flexible framework is presented that tackles these challenges by combining DEM simulations with regression methods. A surrogate model is trained, making it possible to identify parameter combinations in a fast and effective manner. The applicability was proven for a test powder, and multiple varieties of DEM parameters were determined. Due to the analytical structure of the surrogate model, it becomes computational feasibility to combine it with any optimization algorithm.

Effect of various inserts on flow behavior of Fe2O3 beads in a three-dimensional silo subjected to cyclic discharge- Part I: Exploration of transport properties

Optimizations of uniform velocities and residence times of oxygen carriers in chemical looping reactors are key factors. This study firstly applies inserts to improve the flow performance of Fe2O3 beads in an actual 3D reactor. This study proposes a novel DEM approach with null friction boundaries to investigate transport properties of Fe2O3 beads in a reactor with inserts subjected to cyclic discharge. Six inserts were analyzed, e.g., conical insert, disk insert, BINSERT, hollow cylinder insert, and hollow silo insert, as well as no inserts for comparison, respectively. Results revealed that the flow of Fe2O3 beads in the 3D silos with the conical insert, disk insert, and BINSERT exhibited superior uniform velocity profiles. Furthermore, the corresponding granular temperatures and residence times were evener. The installation of these three inserts is more conducive to the uniform discharge of the Fe2O3 beads within a looping reactor.

A DEM approach for simulating flexible beam elements with the Project Chrono core module in DualSPHysics

A DEM approach for simulating flexible beam elements with the Project Chrono core module in DualSPHysics

Modeling of tsunami run-up using terrain model data based on photogrammetry processing product (case study at Way Muli Village, Rajabasa, South Lampung)

Photogrammetry has become a trend in large-scale mapping today. The ability to produce large-scale geospatial products in a relatively short time and low cost is very beneficial for mapping. The ability of high temporal and spatial resolution also makes photogrammetry used in the disaster mapping process. In this study, the DEM approach from photogrammetry was used for input data in tsunami run-up modeling activities in Way Muli Village. High temporal and spatial capabilities are utilized for the production of surface roughness and elevation which are key parameters for rigorous inundation modeling. The modeled inundation results show that the run-up limit achieved in residential areas is on the main road with a maximum distance of inundation from the shoreline is an average of 80 m. The results obtained can be used by the village government to preparedness in dealing with the tsunami.

A coupled CFD–DEM approach to model the in-trough mixing in a multi-stage solar particle receiver

Concentrated solar power (CSP) is expected to reach economic competitiveness with conventional power plants in the foreseeable future. The use of fine-grained ceramic particles as a heat transfer fluid (HTF) for CSP is a promising alternative to other HTFs such as molten salts and nanofluids. However, research on ceramic particle based CSP is stymied due to the inherent difficulty in obtaining in-depth particle mixing processes. Acquiring this highly sought information would allow engineers and scientists to improve the design and optimization of next-generation CSP receivers thereby potentially leading to improved thermal efficiencies. To this end, a high-fidelity numerical model, namely a coupled computational fluid dynamics and discrete element method (CFD–DEM) is developed and implemented on a novel multi-stage solar particle receiver to provide an in-depth analysis of the dynamical and temporal evolution of the in-trough particle mixing processes. The results obtained from this numerical model will assist engineers and scientists to better optimize particle based CSP systems. The validated numerical model accounts for particle–particle, particle–wall, particle–fluid interactions of multiphase solid-gas flows in a novel multi-stage solar particle receiver. This study is the first attempt to conceptualize a novel multi-stage solar and to develop and implement a high-fidelity numerical model to provide an in-depth analysis of the in-trough particle mixing processes. For the first time, important flow characteristics, namely particle mixing, of the particle curtain are investigated. The results showed that the ‘catch-and-release’ troughs have a profound implication on the in-trough mixing process depending on the location of the particle in the particle curtain. The numerical model revealed that specific regions of the multi-stage receiver exhibit high particle residence times and low particle velocities. The rear particle of a curtain takes about 15% longer to reach the 2nd bin compared to the front and centre particle, and the rear particle remains immersed in the 2nd bin for about 14% longer compared to the front and centre particle. As such, the large particle residence time due to the in-trough mixing could potentially lead to better heat transfer performance of a solar receiver. The high-fidelity numerical model could potentially serve as an advanced tool for engineers and scientists to carefully design, optimize, and guide-the scale up and commercialization of novel solar particle receivers, particle heat exchangers, and various other industrial applications such as solar gasification (syngas) and green hydrogen technologies.

A statistical DEM approach for modelling heterogeneous brittle materials

By utilizing numerical models and simulation, insights about the fracture process of brittle heterogeneous materials can be gained without the need for expensive, difficult, or even impossible, experiments. Brittle and heterogeneous materials like rocks usually exhibit a large spread of experimental data and there is a need for a stochastic model that can mimic this behaviour. In this work, a new numerical approach, based on the Bonded Discrete Element Method, for modelling of heterogeneous brittle materials is proposed and evaluated. The material properties are introduced into the model via two main inputs. Firstly, the grains are constructed as ellipsoidal subsets of spherical discrete elements. The sizes and shapes of these ellipsoidal subsets are randomized, which introduces a grain shape heterogeneity Secondly, the micromechanical parameters of the constituent particles of the grains are given by the Weibull distribution. The model was applied to the Brazilian Disc Test, where the crack initiation, propagation, coalescence and branching could be investigated for different sets of grain cement strengths and sample heterogeneities. The crack initiation and propagation was found to be highly dependent on the level of heterogeneity and cement strength. Specifically, the amount of cracks initiating from the loading contact was found to be more prevalent for cases with higher cement strength and lower heterogeneity, while a more severe zigzag shaped crack pattern was found for the cases with lower cement strength and higher heterogeneity. Generally, the proposed model was found to be able to capture typical phenomena associated with brittle heterogeneous materials, e.g. the unpredictability of the strength in tension and crack properties.

The critical state behaviour of granular material in triaxial and direct simple shear condition: A DEM approach

The critical state (CS), the anchor concept in the critical state soil mechanics (CSSM) framework, has been comprehensively evaluated in triaxial stress conditions, where all the principal stresses are known but the pure shear stresses in the shear directions are absent. Therefore, the evolution of first and second invariants of the stress tensor (σ′) i.e. the mean effective stress (p′) and deviatoric stress (q) along with volumetric strain (εv) is often used to identify the CS. However, the same does not apply for a direct simple shear (DSS) test, which is more representative of the real ground condition, as in most cases the minor principal stresses are not measured. This leads to the challenge of determining the CS line in the e-log(p') space and thus the concept of state parameter (ψ) cannot be used to characterise soil behaviour. Using DEM, this study evaluates CS for DSS, using evolution σ′ and εv, in the e-σ'N space, compare its location with triaxial CS lines in the e-log(p') space. The CS line for DSS in e-σ'N space was then used to define a modified state parameter, ψ, (ψm). It was found that both ψ and ψm showed good correlations with characteristic behaviour e.g. onset of liquefaction, phase transformation state, fabric anisotropy etc. Therefore, ψm maybe a good alternative of ψ for DSS test where the minor principal effective stresses are not measured to define a CSL in e-log(p') space.

Extending the Shields criterion to erosion of weakly cemented granular soils

This contribution tackles the issue of incipient conditions for initiation of erosion by a fluid flow at the surface of cohesive materials. To this end, a typical assessment procedure consists of subjecting a soil sample to progressive hydrodynamic stresses induced by a submerged impinging jet flow whose injection velocity is gradually increased. This paper presents the results of an extensive use of this protocol both in experiments and numerical simulations, the latter being based on a coupled DEM and LBM approach. Here we consider the specific case of weakly cemented soils, either made experimentally of glass beads bonded by solid bridges or modelled numerically by a solid bond rheology with a parabolic yield condition involving the micromechanical traction, shearing and bending of the bonds. The results show that, as expected, the hydrodynamic stress for erosion onset substantially increases with solid cohesion as compared to cohesionless cases but can, however, be satisfactorily predicted by a simple extension of the usual Shields criterion that only applies for cohesion-less granular sediments. This extension includes a cohesion number, the granular Bond number, with a simple definition based on tensile yield values.