Computational Fluid Dynamics Discrete Element Method Research Articles

Effects of operating parameters and particle friction on water usage of deep-sea manganese nodules hydraulic conveying equipment

One of the primary concerns for commercialising deep-sea mining is the environmental impact associated with the pumping seawater. Therefore, this study developed an unresolved coupled model of Computational Fluid Dynamics - Discrete Element Method (CFD-DEM) to explore water usage under various operating conditions. The model was validated by experimental results from previous research. The study specifically focused on examining the effects of particle friction on the particle output rate and water usage. The results indicated that to minimise the usage of seawater, the injecting speed should be set at a relatively high value to achieve a high discharge rate, such as 3 m/s in this work. The injecting speed for large particles can be set lower than that for small particles. It is recommended to set the pumping flow rate at a relatively low value, as long as it can generate enough lift force to transport the particles.

Sustainable dye extraction: Annatto powder production in a fountain confined spouted bed

AbstractThis study proposes an efficient and sustainable process for annatto powder production using a fountain confined spouted bed. With widespread applications in industries such as food, pharmaceuticals, and cosmetics, conventional extraction methods face environmental and economic challenges. Our study explores a solvent‐free and eco‐friendly approach using mechanical attrition within a fountain confined spouted bed, offering a cost‐effective solution for annatto cultivation. We systematically investigated the impact of four parameters—fountain confiner position and length, draft tube diameter, and airflow velocity—employing experimental design, multiple regression analysis, particle swarm optimization, and computational fluid dynamics–discrete element method (CFD‐DEM) simulations. The proposed optimization condition shows significantly higher collision intensity, improving annatto powder production compared to other central composite design tests. This study contributes to developing of a sustainable and economically viable method for dye production, with potential implications for annatto‐producing regions globally.

Effects of natural fracture reopening on proppant transport in supercritical CO2 fracturing: A CFD-DEM study

The reopening of natural fractures reshapes the proppant beds in hydraulic fractures, especially at fracture intersections, critically influencing subsequent proppant migration. However, studies on the effects of proppant bed shapes on post-reopening proppant migration are limited. To address this gap, a moving wall boundary technique is integrated into a Computational Fluid Dynamics–Discrete Element Method (CFD-DEM) framework to model natural fracture reopening, enabling an in-depth analysis of how proppant bed reshaping impacts subsequent proppant migration during supercritical CO2 fracturing. Results reveal that proppant migration into natural fractures is governed by both drag force-induced and gravity-induced rolling mechanisms, with the latter exerting a more significant effect. The gravity-induced rolling mechanism is enhanced by five key factors: (a) the generation of a well-developed proppant pack in proximity to the intersection; (b) the inadequately filled V-shaped gully; (c) the increased proppant transport capacity within the natural fracture; (d) the reduced bypassing of proppants at the intersection; and (e) the improved ability of proppants to enter the natural fracture. The enhanced gravity-induced rolling mechanism significantly increases the proppants flowing into natural fractures: by 35.6% between the central and rearward section cases, 168.9% from mild to severe plugging cases, 39.1% with a wider natural fracture width (1.5 mm–2.5 mm), 20.3% with decreased hydraulic fracture flow rate (0.35 m/s to 0.25 m/s), and 33% with reduced fluid temperature (160 °C–40 °C). These findings underscore the impact of natural fracture reopening on subsequent proppant migration, offering valuable insights for optimizing fracturing designs.

Particle dynamic behaviors in bubble curtain barriers blocking the diffusion of sediment

Bubble curtains are linear multiphase plumes that are used in industry and engineering to reduce diffusive flows between two zones. The circulating shear flow generated by the bubble plume can effectively create a particle barrier in the water; thus, it is also widely used to suppress the diffusion of suspended particles during dredging operations. To clarify the interaction mechanism between the bubble curtain and suspended particles under pressure-driven flow, experimental studies and numerical simulations were conducted to investigate the particle dynamics in the flow field around the bubble curtain. In this study, we established a formal analogy between a bubble curtain and an air curtain and qualitatively identified four typical distribution zones of the particles in the flow field. Based on the quantitative measurements and theoretical considerations, the optimal operating conditions and the upper limit of effectiveness of the bubble curtain were determined. In addition, the blocking behavior and efficiency of bubble plumes on particles with different ReU and FrUgnumbers and different particle properties were simulated via the computational fluid dynamicsdiscrete element method (CFDDEM) numerical simulation method.

Impact of several coarse-graining models on a pilot-scale fluidized bed behavior using discrete element method–computational fluid dynamics

Impact of several coarse-graining models on a pilot-scale fluidized bed behavior using discrete element method–computational fluid dynamics

Fully coupled discrete element method for graded particles transport in pipes

Hydraulic conveying of graded particles is much more complex than that of uniform particles but is not fully understood. A fully coupled computational fluid dynamics–discrete element method model is established for the hydraulic conveying of graded particles, which integrally considers the particle–fluid and particle–particle interactions and turbulence modulation from particles. The proposed model accounts for the stochastic motion of particles by the discrete random walk method and applies the diffusion averaging algorithm to obtain particle concentration in arbitrary cells for smooth and cell-independent data fields on unfavorable cells (fluid cell size ≤ particle size). The particle–fluid drag force is applied to slurry flows through densely packed particle beds due to the consideration of porosity modification. The proposed model well performs in simulating the hydraulic conveying of dense graded particles. Dynamics in slurry mixtures of bi-disperse particles are investigated regarding different particle size compositions. The results show obvious stratification between coarse and fine particles, e.g., fine particles settling at the pipe bottom elevate the coarse particles and form a “lubrication layer” with high velocity. The torque caused by particle–particle/wall contact is greater than the torque caused by the fluid. The pipe cross section is divided into four regions according to the particle angular velocity. The effect of particle concentration on liquid motion is small because the difference in local particle concentration is relatively small, but the maximum pressure drop corresponds to a critical particle size composition.

Structural Design of Pressurized Tube Based on the Discrete Element Method–Computational Fluid Dynamics Coupled Simulation

In order to elucidate the impact of pressurized tubes’ structures on the sowing performance of pneumatic seed delivery systems, the EDEM–CFD coupled simulation method was employed to analyze the influence of pressurized tube parameters, including length (L), corrugation depth (S), corrugation width (K), and the number of corrugations, on seed movement characteristics, distribution uniformity, and airflow patterns. Simulation-validated experiments were conducted to study the impact of the optimal pressurized tube structure on seeding performance. The results indicate that pressurized tubes significantly enhance the uniformity coefficient of seed distribution, reduce seed velocity, and decrease the coefficient of variation in distribution uniformity. When pressurized tube parameters, specifically length (L), corrugation depth (S), corrugation width (K), and the number of corrugations, are set at 800 mm, 8 mm, 50 mm, and 6, respectively, the uniformity coefficient of seed distribution exceeds 95%, and the coefficient of variation in seed discharge consistency for each row is less than 3.2%. Moreover, the seed velocity at the outlet of the pressurized tube, the relative velocity of two-phase flow, and pressure loss are all minimal, indicating superior seeding performance. This research provides valuable insights into the analysis of seed movement characteristics within pressurized tubes and the optimization of their structural parameters.

Controlling of cellular substructure and its effect on mechanical properties of FeCoCrNiMo0.2 high entropy alloy fabricated by selective laser melting

Fine cellular substructures are typical microstructure feature of high entropy alloys (HEAs) produced via selective laser melting (SLM), playing a pivotal role in improving the mechanical properties. Nonetheless, the controlling of cellular substructure and its impact on the mechanical properties remains ambiguous. This study investigates the effect of energy densities on the cellular substructure evolution and mechanical properties of the FeCoCrNiMo0.2 HEA. It is found the increase in energy density causes a decrease in temperature gradient (G) and solidification rate (R) in molten pool, consequently leading to the increase of cellular substructure size and the intensification of Mo segregation at cellular substructure boundaries. The cellular substructure size (d) can be described by formula d=80(GR)−1/3, in which G and R can be obtained from discrete element method - computational fluid dynamics (DEM-CFD) simulation. The strength of the FeCoCrNiMo0.2 HEA is significantly affected by dislocation strengthening (σd) and segregation strengthening (σs), which are further determined by the cellular substructure size and the Mo segregation, respectively. The increase of cellular substructure size leads to the decrease of σd, while the intensification of Mo segregation results in the increase of σs. The competition between these two strengthening effects leads to an optimized and excellent tensile property of 707 MPa in yield strength, 947 MPa in ultimate tensile strength and 34 % in fracture elongation at a moderate energy density of 47 J/mm3. The findings provide guidance towards the advancement of high-performance high entropy alloys fabricated by SLM in terms of cellular substructure controlling.

Research on the Grinding Process of Superhard Particles in the Fluidized Bed Opposed Jet Mill Based on the CFD-DEM Methodology

The process of superhard particle breakage in the grinding zone of the fluidized bed opposed jet mill is investigated using the CFD-DEM (computational fluid dynamics-discrete element method) coupling method with the Tavares UFRJ Breakage Model in the present study. The effects of structural and operational parameters, such as target plate structure, nozzle position, air inlet velocity, and feed rate, on the equipment stress distribution, airflow velocity, pressure field, particle velocity, and cumulative particle size distribution are thoroughly studied to determine the optimal structural and operational parameters. Experimental validation is conducted, including scanning electron microscope (SEM) observation of particle morphology and analysis of particle size distribution of ground product particles. The simulation results indicate that the wear rate of the structure without a target plate is lower than that of the structure with a target plate in the grinding central zone. Therefore, the structure without a target plate is chosen for further investigation. The cumulative particle size distribution after grinding is influenced by nozzle position, air inlet velocity, and feed rate. The particle D50 is positively correlated with nozzle spacing and feed rate, while it is negatively correlated with air inlet velocity. The optimal grinding effect is achieved when the distance between the nozzle and the center of the grinding zone ranges from 52.5 mm to 72.55 mm, the air inlet velocity is 950 m/s, and the feed rate is 10.5 g/s. Through experimental investigation, it has been observed that when the feed rate is 10 g/s, the particle size distribution becomes more uniform. Furthermore, consistent trends in the cumulative particle size distribution in the experiment and simulation results can be found, which validates the present numerical model. It was observed that particles at low feed rates retain certain angular edges, while particle roundness increases at high feed rates.

Numerical Modeling of Foam Carrying Sand Transport in Multifactor Horizontal Wells.

The solution of wellbore multiphase flow models has an important position in oil-gas field development. However, the solution of multiphase flow models often involves a series of complicated situations such as interphase mass and energy transfer, surface problems, and so on. Foam carrying sand particles in the wellbore is a solid, liquid, and gas three-phase cylinder flow problem. To solve this problem, we developed a computational fluid dynamics-discrete element method model based on the traditional N-S equations to track the streamline of the foam fluid and sand particles in the wellbore. On this basis, we investigated the influence of three factors, i.e., foam and sand properties and wellbore parameters, on the sand carrying rate of foam. The results show that whether the sand mound at the bottom of wells that can be dispersed is mainly affected by the properties of foam. The location of sand deposition in the wellbore and the effectiveness of foam in sand transportation are mainly influenced by the wellbore parameters and sand properties.

Fully Coupled CFD–DEM Simulation of Oil Well Hole Cleaning: Effect of Mud Hydrodynamics on Cuttings Transport

This paper presents a coupled computational fluid dynamics–discrete element method (CFD–DEM) simulation to predict cuttings transport by the drilling fluid (mud) in different oil well drilling conditions. The mud rheology is expressed by the Herschel–Bulkley behaviour and modelled in a Eulerian framework (CFD), while the cuttings are modelled using the Lagrangian approach (DEM). In this work, the effects of drill string rotation, inclination angle, cutting size, mud rheology, and annular velocity on cleaning efficiency are investigated. It is found that increasing the well deviation from vertical to horizontal leads to a higher cuttings concentration. However, at low annular velocity, the cuttings concentration for the inclined (45-degree) annulus is found to be higher than the horizontal one due to the sliding motion of cuttings on the lower section of the annulus. Overall, the drill pipe rotation has little effect on decreasing the cuttings concentration, but the effect is more pronounced at low annular velocity.

A modified CFD-DEM method for accurate prediction of the minimum fluidization velocity

Monodisperse fluidized bed experiments have been carried out on 13 kinds of particles with different particle sizes in a cylindrical fluidized bed. The accuracy of nine commonly used monodisperse drag models, including the Gidsapow, BVK, and Zhou–Fan models is verified. It is found that the Zhou–Fan model is the most accurate at low and moderate values of the particle Reynolds number. It is found that with the traditional computational fluid dynamics–discrete element method (CFD-DEM) method it is difficult to obtain an accurate minimum fluidization velocity owing to difficulty in obtaining an accurate value of the minimum fluidization solid volume fraction. A modified method is proposed to increase the accuracy of prediction of the minimum fluidized solid volume fraction by using a virtual particle size in the calculation of the particle collision process. The effectiveness of the modified method is verified by comparing the CFD-DEM simulation results with experimental results for Geldart-D particles. The relative error of the minimum fluidization velocity is found to be reduced from 24.6% to 2%.

Gas–solid flow mechanism of spherocylindrical particles with various aspect ratios in spouted bed

Spherocylindrical particles encompass elongated spherical particles, such as biomass particles utilized in thermal reactions and capsule pills in the pharmaceutical industry, along with various other particles found in industrial production processes. Understanding the flow behavior of spherocylindrical particles within a spouted bed holds significant practical importance. This study delves into investigating the fluidization characteristics of spherocylindrical particles with varying aspect ratios within a spouted bed. Key parameters studied include particle void fraction, velocity, orientation, and mixing. These were analyzed using the computational fluid dynamics–discrete element method, and the simulation model's accuracy was verified through high-speed photography experiments. The findings revealed distinct void fraction distributions at different locations within the bed. Particles in the higher-bed region exhibited larger void fractions with flatter peaks compared to those in the lower-bed region. Moreover, the correlation between particle aspect ratio and void fraction varied at different heights within the bed. Notably, there was no significant correlation observed between particle aspect ratio and particle velocity. However, the larger the particle aspect ratio/gas velocity, the better the particle mixing quality. Additionally, gas velocity and particle aspect ratio had little effect on particle orientation, but there was a tendency for particle orientation angles to hover around 45°–60° near the wall region.

Design of closed loop for reproduction of gas-dominated hydrate flow.

The study presents a novel setup for measuring the flow regime of hydrate particles in a gas-dominated flow, which is of interest for applications such as natural gas transportation. A closed-flow loop, driven by a novel internal fan, enables continuous observation of hydrate particle behavior in a gas flow. The experimental setup allows the production and insertion of HFC134a gas hydrate particles with diameters of 10-50μm into the gas flow loop via a bypass loop. The performance curve of the internal fan is validated, and its suitability for achieving the required flow speed (5m/s) is demonstrated. Through an observation window using camera systems, the flow regime of glass beads is successfully visualized and analyzed. To validate the experimental data, a coupled computational fluid dynamics-discrete element method model is used to simulate the particle flow density distribution. The study findings demonstrate the effectiveness of the experimental setup in characterizing the flow regime of hydrate particles in a gas-dominated flow.

Effects of nozzle angles of a double-row jet collector on harvesting performance

Owing to its high collection efficiency, the double-row jet collector is an important application in industrial operations. Presently, few studies on its collection efficiency and impact from its front and rear nozzle angles are available. In this paper, the computational fluid dynamics–discrete element method is employed to numerically study the jet parameters of a typical double-row jet collector from three aspects: flow characteristics, particle movement and collection efficiency. Defining α as the front nozzle and β as the rear nozzle, five different combinations of jet angles were first selected and an optimal configuration of the front nozzle at 30°and the rear nozzle at 55° was last obtained, the simulation results were confirmed via the performance experiment. The influence of the change in the front and rear jet angles on the flow field of the collection is shown, and the results indicate that of the angle α and β, α plays a dominant role, while β has relatively little influence on the whole collecting process, which guides for the optimal design.

Novel drag and Nusselt number models based on direct numerical simulations of a bidisperse gas–solid system

AbstractFlow and heat transfer in a bidisperse gas–solid system with freely moving spheres are simulated by particle‐resolved direct numerical simulation (PR‐DNS). Gas–solid coupling is enforced by the direct‐forcing immersed boundary method. Compard with the DNS database, it is found that the existing polydisperse drag correction model developed from static systems combined with various monodisperse drag models underestimates the drag force on dynamic arrays of particles. The existing Nusselt number correction model developed from static systems combined with various monodisperse models overestimates the Nusselt number of dynamic arrays of particles. Sensitivity analysis indicates that the effects of the granular temperature on the drag force and Nusselt number are negligible. Novel polydisperse drag and Nusselt number models are derived based on the database. The advantages of the derived polydisperse drag and Nusselt number models are demonstrated and confirmed by comparing the results of the computational fluid dynamics–discrete element method using various drag and Nusselt number models with experimental or additional PR‐DNS data.

Study on the Mechanism of Water and Sand Leakage in a Foundation Pit Retaining Structure Based on the Computational Fluid Dynamics–Discrete Element Method

The existence of defects in the enclosure structure is the primary cause of water and sand leakage in foundation pits, as well as being a significant source of danger in pit construction, but current research lacks an in-depth investigation of the generation mechanism and gestation process. In this paper, which comprehensively considers the microscopic particles and macroscopic level, the development mechanism of a water and sand leakage disaster in a foundation pit with a water-rich sand layer was studied using the principle of computational fluid dynamics and discrete element method coupled analysis (CFD–DEM); moreover, based on the anisotropy of the particle force and fluid energy analysis, the deformation of the stratum and ground stress field were analyzed. The results show that the stress field will produce a plugging effect at a certain distance from the defect, and the strata exhibit a dominant displacement tendency in the vertical direction, resulting in the emergence of a gradually concave stress relaxation zone and an elliptical contour in the strata displacement map near the defect. The fluid energy describes the displacement of the sand layer very well, and it is separated into the sand layer’s centralized loss region and the major loss area based on the high and low levels of the fluid energy class. The impact of fluid at the defect reaches the maximum kinetic energy, which penetrates the structural weakness and causes the loss of sand particles, and the cross-section of the water influx near the defect gradually expands with the loss of particles, indicating that there is a danger of further expansion of the defect under the impact of water flow. These results have technical implications for the management of water and sand leakage disasters in foundation pit engineering.

Simulation of proppant conductivity test: effect of particle size dispersion

A conductivity test of proppant material consists in confining a sample of the granulate at high pressure and then set a flow through the pack. The proppant particle size is the main variable controlling conductivity, but also particle size dispersion is considered important. Even though several studies consider mixtures of proppants of different meshes, there are not clear evidences as to whether the changes in conductivity with respect to a monosized proppant are caused by the mix itself or by the overall change in mean particle size. Hence, we use numerical simulations to answer the question: Does particle size dispersion significantly affects the proppant conductivity if mean particle size is kept the same? We measure conductivity and permeability by simulating (via a coupled Computational Fluid Dynamics–Discrete Element Method) the flow of water through binary granular packs. We find that size dispersion does not affect conductivity (in the dispersion range explored) if the mean particle size is conserved. However, we observe that in a binary mixture the large particles are subjected to larger stresses than in a monosized system, which makes them prone to crushing.

Settling dynamics and thresholds for breakup and separation of bi-disperse particle clouds

Settling dynamics and thresholds for breakup and separation of bi-disperse particle clouds

An improved semi-resolved computational fluid dynamics-discrete element method for simulating liquid–solid systems with wide particle size distributions

Vertical hydraulic transport of particles with wide particle size distributions is a crucial process for coal physical fluidized mining. In the present study, an improved semi-resolved computational fluid dynamics (CFD)-discrete element method was developed to simulate particle flows with wide particle size distributions. In this model, the CFD cells allocated to the particle volume and the momentum source term were defined as the dependent domain and the influential domain, respectively. On this basis, the two-way domain expansion method and the one-way domain expansion method were adopted for the liquid–solid simulation of coarse and fine particles, respectively. The dependent domain expansion coefficient and the influential domain expansion coefficient were proposed to determine the spatial range of the dependent domain and influential domain for the coarse particles, and the optimal modeling strategy for the dependent domain and influential domain expansion coefficient for the coarse particles was determined. Furthermore, a volume expansion method and a momentum source expansion method were proposed for calculating the solid volume fraction of the dependent domain and the source term of the influential domain for the coarse particles. Furthermore, the sample point method was adopted to obtain the solid volume fraction in the dependent domain for the fine particles, and the momentum source term was only updated to the particle-located cell. Subsequently, single-particle settling and binary-particle fluidizing numerical experiments were used to verify the calculation accuracy of the model. The investigation can provide a new method for numerical simulation of liquid–solid flow with wide particle size distributions.