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Suffusion is a critical issue in geotechnical engineering. Despite extensive studies, the effect of soil specimen dimensions on suffusion remains unclear. In this paper, a coupled computational fluid dynamics and discrete element method (CFD-DEM) approach is employed to study the suffusion of gap-graded soils with varying aspect ratios, and the underlying physical mechanisms are discussed. The results indicate that as the aspect ratio increases, erosion degree, mechanical coordination numbers, and unevenness in the fines distribution decrease, while the likelihood of fine particles integrating into the soil skeleton rises. Before suffusion, specimens with lower aspect ratios show higher peak strengths. After suffusion, peak strength decreases with erosion degree. However, all specimens exhibit comparable residual strengths. The mechanism behind different suffusion behaviors in specimens with varying aspect ratios is primarily governed by their unique suffusion boundary conditions. Accounting for suffusion boundaries significantly modify erosion laws and eroded soil mechanics behaviors. A standardized specimen size is proposed to account for suffusion boundary effects, thereby minimizing errors attributed to variations in outlet sieve aperture sizes and inconsistencies in specimen dimensions. The results obtained highlight the influence of specimen size on suffusion, advancing our precise understanding of eroded soil behavior. [ABSTRACT FROM AUTHOR]

To analyze the differences in the transport and distribution of different types of proppants and to address issues such as the short effective support of proppant and poor placement in hydraulically intersecting fractures, this study considered the combined impact of geological-engineering factors on conductivity. Using reservoir production parameters and the discrete element method, multispherical proppants were constructed. Additionally, a 3D fracture model, based on the specified conditions of the L block, employed coupled (Computational Fluid Dynamics) CFD-DEM (Discrete Element Method) for joint simulations to quantitatively analyze the transport and placement patterns of multispherical proppants in intersecting fractures. Results indicate that turbulent kinetic energy is an intrinsic factor affecting proppant transport. Moreover, the efficiency of placement and migration distance of low-sphericity quartz sand constructed by the DEM in the main fracture are significantly reduced compared to spherical ceramic proppants, with a 27.7% decrease in the volume fraction of the fracture surface, subsequently affecting the placement concentration and damaging fracture conductivity. Compared to small-angle fractures, controlling artificial and natural fractures to expand at angles of 45° to 60° increases the effective support length by approximately 20.6%. During hydraulic fracturing of gas wells, ensuring the fracture support area and post-closure conductivity can be achieved by controlling the sphericity of proppants and adjusting the perforation direction to control the direction of artificial fractures. [ABSTRACT FROM AUTHOR]

AbstractThe prefabricated vertical drain (PVD) alleviating clogging mechanism under different air injection pressure and time is not clear for air-boosted vacuum preloading. The computational fluid dynamic-discrete element method (CFD-DEM) is developed to dynamically observe PVD clogging and investigate the PVD clogging mechanism. i.e., PVD discharge rate, soil particle migration, and porosity change under the different air injection patterns of vacuum preloading with no air injection, constant air injection pressure of 75 kPa, and variable air injection pressure of 25∼150 kPa. Compared with conventional vacuum preloading with no air injection, the water discharge rate of PVD can be increased, clogging layer area can be reduced significantly for air-boosted vacuum preloading. The porosity near the air injection port is greater than that close to the PVD. The consolidation mechanism of air-boosted vacuum preloading the disturbance effect in the early stage of consolidation, the pressurization effect in the middle stage of consolidation, and the clogging effect in the later stage of consolidation are revealed. Three kinds of laboratory model tests are run to demonstrate air injection alleviating PVD clogging. The results demonstrate that increasing the air injection pressure can significantly alleviate PVD clogging. [ABSTRACT FROM AUTHOR]

Coarse particles in filling slurry are the primary factor causing wear in filling elbow pipes, and the wear mechanism of these particles on the pipes is influenced by various factors. To study the erosion and wear mechanism of elbow pipes caused by coarse particles, the motion state of coarse particles under different curvature radii, coarse particle gradations, and pipe diameters was investigated using a simulation method based on the coupling of Fluent and EDEM software, grounded in theories of fluid mechanics, rheology, and solid–liquid two-phase flow. The study explored the impact patterns and locations of wear induced by coarse particles on filling elbow pipes. The analysis results indicate that increasing the curvature radius leads to more punctate wear at the elbow and upstream wear. Increasing the proportion of finer particles in the coarse particle gradation forms a better cushioning layer and reduces erosion wear. Enlarging the pipe diameter shifts the high-low concentration boundary of coarse particles towards the elbow outlet and reduces erosion wear. The research findings provide significant references for optimizing coarse particle gradation and preventing pipe wear. [ABSTRACT FROM AUTHOR]

AbstractTraditional soil thermal desorption often leads to substantial energy loss, particularly with high-moisture soils. A novel approach was proposed, utilizing waste heat from flue gas to pre-dry the soil. A large-scale rotary kiln, with a capacity of 20 t/h, was tested, and the drying process was modeled using CFD-DEM. Results showed the rotary kiln exhibited high stability, enhanced loading capacity, and significant moisture content reduction. Sensitivity analysis indicated that the inlet flue gas temperature had the most significant impact on the outlet moisture content. The rotary kiln’s volumetric heat transfer coefficients ranged from 142.22 to 178.14 W/(m3·°C) and energy utilization rate peaked at 0.81, while the exergy efficiency remained approximately 0.5, demonstrating high energy utilization and exergy efficiency. Detailed analysis of soil particles along the kiln revealed a novel multi-stage drying mechanism. The model effectively describes the drying process, offering valuable insights for future design. [ABSTRACT FROM AUTHOR]

The fluidisation of spherocylindrical particles is often involved in the fields of biomass combustion, drug delivery and food drying. By spherocylindrical particles, we mean elongated spherical particles like non-spherical capsule pills and pulverised biomass fuels. Mastering the fluidisation state of spherocylindrical particles can improve the related industrial processes. In this paper, a coupled CFD–DEM method is used and the reliability of the model in this paper is verified with the help of high-speed photography experiments. Subsequently, the fluidisation characteristics of spherocylindrical particles in a spouted bed were investigated under different operating conditions and compared with the simulation results of spherical particles. The results show that the gas velocity influences the average bed height, axial velocity, volume fraction, orientation angle, and mixing mass of the particles. There are also significant differences in the fluidisation characteristics of particles at different bed heights. The particles in the higher bed region are more dispersed, the gas–solid mixing is more intense, and the gas velocity has a strong influence on the volume fraction/axial velocity of the spherocylindrical particles in the higher bed. In addition, this work also found significant differences in the fluidisation characteristics of different shaped particles. [ABSTRACT FROM AUTHOR]

Understanding the thermal conditions inside a burning cigarette is a top priority for controlling chemical emissions and cigarette design. Since experimental methods are difficult to observe in depth, this paper starts from the perspective of numerical simulation and models the structure of the tobacco distribution of the cigarette, integrating the end surface ignition model, puffing model, chemical reaction model, heat and mass transfer and diffusion model have established a three-dimensional comprehensive model that can represent the changes in combustion cone morphology during cigarette combustion. The model covers chemical reaction and mass transfer as well as generation, flow and reaction mechanism. The simulation results show that the model can better predict the temperature distribution, component distribution and combustion cone morphology changes during cigarette smoking and combustion. It provides an effective means for in-depth research on cigarette combustion. [ABSTRACT FROM AUTHOR]

Ratooning rice plants have a high moisture content and strong adhesion during harvesting. Traditional cleaning devices are prone to clogging when processing ratooning rice, resulting in a series of problems such as high grain loss rate and high grain impurity rate. In response to the above issues, this article adopts the CFD-DEM coupling method to design a spiral step cleaning device. A detailed analysis was conducted on the influence of the cone angle and thickness of the spiral-stepped skeletons on the flow state, and flow velocity and pressure distribution cloud maps were obtained under different structural parameters. The vortex morphology under different thicknesses of the spiral-stepped skeletons was compared, and the structural parameters of the device were determined. The motion trajectory and distribution of impurity particles under different inlet flow velocities were analyzed using data superposition, and the appropriate inlet flow velocity range was determined. A test bench was built, and a three-factor quadratic regression orthogonal rotation combination experiment was conducted with fan speed, feeding rate, and device inclination angle as experimental factors. The results of the bench test show that the performance index reaches its optimum when the device inclination angle, fan speed, and feeding rate are 2.47°, 2906 r/min, and 4.0 kg/s, respectively. At this time, the grain impurity rate, grain loss rate, and sieve clogging rate are 2.21%, 2.15%, and 3.5%, respectively. Compared to those of traditional cleaning equipment, these value are reduced by 44.5%, 39.6%, and 83.9%, respectively. This study can provide ideas for the design of ratooning rice cleaning devices. [ABSTRACT FROM AUTHOR]

Frazil ice is the foundation for all other ice phenomena, and its spatiotemporal evolution is critical for regulating ice conditions in rivers and channels, as well as for preventing and controlling ice damage. This paper investigates the dynamic transport pattern of frazil ice during the early stages of winter freezing in water conveyance channels based on a CFD-DEM coupled numerical model, and derives predictive formulae for the spatiotemporal evolution of frazil ice and floating ice. First, static repose angle simulations and slope sliding simulations were used to calibrate the contact parameters between frazil ice particles and between frazil ice and the channel bed, ensuring the accurate calculation of contact forces in the model. On this basis, the processes of frazil ice transport, aggregation, and upward movement in water transfer channels were simulated, and the influence of contact parameters on simulation results was analyzed, showing a significant effect when the ice concentration was high. Numerical results indicate that the amount of suspended frazil ice is positively correlated with the frazil ice generation rate and water depth, with minimal influence from the flow velocity; the amount of floating ice increases linearly along the channel, with growth positively correlated with the frazil ice generation rate and water depth, and negatively correlated with the flow velocity. Predictive formulae correlating frazil ice and floating ice amounts with the flow velocity, water depth, and other factors were proposed based on numerical results. There is good agreement between the predictive and numerical results: the maximum APE between the predicted and simulated values of suspended frazil ice is 13.24%, and the MAPE is 6.32%; the maximum APE between the predicted and simulated values of floating ice increment is 7.80%, and the MAPE is 2.89%. The proposed prediction formulae can provide a theoretical basis for accurately predicting ice conditions during the early stages of winter freezing in rivers and channels. [ABSTRACT FROM AUTHOR]

Jet pumps are widely used in petrochemical processes, nuclear cooling, and wastewater treatment due to their simple structure, high reliability, and stable performance under extreme conditions. However, when transporting solid-laden two-phase flows, they face severe erosion problems, leading to reduced efficiency, malfunctions, or even failure. Therefore, optimizing jet pump performance and extending its service life is crucial. In this study, an experimental platform was established to conduct experiments on wall erosion in jet pumps. The CFD-DEM method was used to simulate the solid–liquid two-phase flow in the jet pump, comparing six erosion models for predicting erosion rates. The Grey Wolf Optimization algorithm was applied to calibrate model coefficients. The results indicate that the Neilson erosion model shows the best consistency with the experimental results. The inlet flow rate significantly influenced the erosion rates, while the flow rate ratio had a smaller effect. The particle concentration exhibited a nonlinear relationship with erosion, with diminishing impact beyond a certain threshold. As the factors varied, the erosion distribution tended to be uniform, but high erosion areas remained locally concentrated, indicating intensified localized erosion. [ABSTRACT FROM AUTHOR]

Channel fracturing technology is designed to form fractures supported by non-uniform pillar proppants. Non-cured adhesive resin-coated proppant gradually becomes viscous after immersion and agglomerates during transportation. The pillars are stable after the fracture is closed. They not only maintain a certain compressive strength but also maintain long-term conductivity. Currently, there are few evaluations of coated proppant migration. Based on CFD-DEM method, a two-phase flow coupling model considering the adhesive contact force of coated proppant particles is established to study the cementation characteristics of coated proppant during transportation. The transportation mechanism of coated proppant are revealed by numerical calculation analysis. The results show that different from the conventional proppant, the migration process of the coated proppant is divided into four stages (1) the softening of the proppant contact; (2) the paving of the proppant agglomeration; (3) proppant pillars growth along fracture height; and (4) proppant pillars growth along fracture length. We have completed a preliminary geometric characteristics evaluation of sand bank formed by coated proppant by evaluating the pore volume ratio (the ratio of void volume between pillars to the sand bank volume) under various parameters. This evaluation offers some theoretical guidance for the optimization of channel fracturing proppant injection parameters. [ABSTRACT FROM AUTHOR]

The fluidized bed is a critical reactor in the energy and chemical industries, where the mixing and agglomeration behaviors of binary particles significantly influence both the efficiency of reaction processes and the uniformity of final products. However, the selection of appropriate drag force models remains a subject of debate due to the variability in particle properties and operating conditions. In this study, we investigated the fluidization behavior of binary mixtures composed of two different sizes of Geldart-D particles within a fluidized bed, evaluating nine distinct drag force models, including Wen and Yu; Schiller and Naumann; Ergun; Gidaspow, Bezburuah, and Ding; Huilin and Gidaspow; De Felice; Syamlal and O'Brien; and Hill, Koch, and Ladd. We focused on four key parameters: particle mixing degree, migration characteristics, temperature variation, and mean pressure drop. Simulation results revealed that the choice of drag model markedly affected mixing behavior, migration dynamics, and temperature distribution. Notably, the Ergun; Gidaspow, Bezburuah, and Ding; and Hill, Koch, and Ladd models exhibited superior particle mixing uniformity. While the drag model had a relatively minor impact on particle temperature changes, its selection became critical in simulations requiring high-temperature precision. Regarding pressure drop, the Huilin and Gidaspow and Gidaspow, Bezburuah, and Ding models demonstrated smaller and more stable pressure drop fluctuations. These findings offer valuable theoretical insights into gas–solid two-phase flow under binary particle mixing and provide practical guidance for the design and operation of fluidized bed reactors. [ABSTRACT FROM AUTHOR]

The current straw micro-crusher is often utilized within a circular crushing chamber, leading to the formation of a circulation layer that impacts the efficiency of crushing. This study proposes an airfoil crushing chamber to disrupt the circulation layer and modify particle motion characteristics. Based on CFD-DEM analysis with flow field characteristics, motion trajectory, crushing rate, motion speed, and force magnitude as evaluation indices, the crushing performance and flow field distribution of both chamber types are compared. Test results indicate that the airfoil crushing chamber outperforms the circular one, thereby validating the accuracy of the theoretical and numerical analyses. [ABSTRACT FROM AUTHOR]

Centrifugal slurry pumps are extensively applied in industrial industries such as power metallurgy, petrochemicals, deep-sea mining, and other industrial fields. The primary objective of this research is to assess how conveying settings and particle characteristics influence the 100SHL4147 slurry pump's collision and erosion properties. Firstly, the computational fluid dynamics–discrete element method (CFD-DEM) coupling model fully coupled particle–fluid co-flow numerical simulation interface is built by utilizing the C++ language and the results are proven with tests. Subsequently, the simulation examines the wear properties of different sections through which the flow passes in the 100SHL4147 centrifugal slurry pump. In addition, following theoretical guidance, the slurry pump impeller's wear resistance performance can be improved by adjusting design factors such as the intake edge location and the blade wrap angle. The results are as follows. It is recommended to replace the impeller promptly due to the findings that indicate that the entire blade's pressure surface is vulnerable to different degrees of erosion under high-concentration situations. When the particle size increased from 0.4 to 0.8 mm, the wear rate decreased by up to 15%, as fewer particles were transported, lowering the collision frequency. Conversely, smaller particles intensify component wear. Adjusting the blade wrap angle from 66° to 96° reduced impeller and volute wear by an estimated 20%, enhancing the durability but slightly decreasing the delivery capacity. Extending the blade's leading edge toward the intake improved the flow capacity, although it increased the wear frequency from one-third of the pressure surface to the trailing edge. [ABSTRACT FROM AUTHOR]

The quality of crushing, power consumption, and discharging performance of a straw crusher are greatly influenced by the characteristics of its internal flow field. To enhance the straw crusher's flow field properties and improve the efficiency with which crushed material is discharged, first, the main structural parameters influencing the air flow in the crusher are discussed. Then, the coupled gas-solid flow field in the straw crusher is numerically calculated through solution of the Navier-Stokes equations and application of the discrete element method (DEM). Finally, the discharge performance index of the crusher is examined through detailed analysis of the crushed material dynamics. Additionally, a multi-island genetic algorithm is used to optimize the structure and operational factors that have significant effects on the discharge performance. With optimization, the accumulation rate of crushed materials in the bottom region of the straw crusher decreases by 20.08%, and the mass flow rate at the discharge outlet increases by 11.63%. [ABSTRACT FROM AUTHOR]

Abstract Coarse particles in filling slurry are the primary factor causing wear in filling elbow pipes, and the wear mechanism of these particles on the pipes is influenced by various factors. To study the erosion and wear mechanism of elbow pipes caused by coarse particles, the motion state of coarse particles under different curvature radii, coarse particle gradations, and pipe diameters was investigated using a simulation method based on the coupling of Fluent and EDEM software, grounded in theories of fluid mechanics, rheology, and solid–liquid two-phase flow. The study explored the impact patterns and locations of wear induced by coarse particles on filling elbow pipes. The analysis results indicate that increasing the curvature radius leads to more punctate wear at the elbow and upstream wear. Increasing the proportion of finer particles in the coarse particle gradation forms a better cushioning layer and reduces erosion wear. Enlarging the pipe diameter shifts the high-low concentration boundary of coarse particles towards the elbow outlet and reduces erosion wear. The research findings provide significant references for optimizing coarse particle gradation and preventing pipe wear.

Accurately assessing the erodibility of geomaterials is of great significance for the design of earthen structures and the prevention of the associated failure induced by seepage force. Recently, the un-resolved Computational Fluid Dynamics–Discrete Element Method (CFD–DEM) has been widely used to investigate internal erosion. However, due to the use of wall boundary and the fact that the fixed CFD domain cannot be changed with the soil sample's volume contraction during the erosion test, a larger porosity at the boundary of the CFD domain is commonly formed, resulting in sidewall preferential flow (i.e., relatively more fine particles migrate along the boundary of the DEM domain) and thereby overestimating the soil erodibility. In this study, a new method based on particle boundary is developed to tackle this problem. The newly proposed particle boundary can prevent its particles from erosion via inter-particle bonding and transfer stress from servo walls to the simulated sample. An optimal particle boundary thickness is determined by considering sample contraction and computational efficiency. The performance of the new method was compared with the conventional method and also verified using experimental results. The results show that the newly proposed method has significantly improved the uniformity of fluid velocity distribution. Furthermore, the cumulative eroded mass of fine particles in the new model is approximately 15% lower than in the conventional model. It is convincingly demonstrated that the new method can simulate internal erosion better and give a more accurate assessment of geomaterial erodibility. [ABSTRACT FROM AUTHOR]

In this study, we present a successful application of the Computational Fluid Dynamics–Discrete Element Method (CFD–DEM) for simulating the complex phenomenon of multi-particle arch formation within high-concentration packed-bed environments. We investigate the roles of physical forces in this phenomenon, shedding light on aspects that are challenging to explore through experimentation. Our research is motivated by the desire to comprehend the conditions and parameters influencing the formation, stability, disruption, and reformation of multi-particle sand arches within filter openings. This arching phenomenon serves as an efficient particle retention mechanism, particularly in heavy oil production wells. We delve into factors like particle size, shape, and particle size distribution that may impact multi-particle arch performance. Additionally, we explore the physics behind multi-particle arching by examining the effects of various physical forces on arch performance. Utilizing a Computational Fluid Dynamics–Discrete Element Model, we investigate the multi-particle arching phenomenon under steady-state flow conditions in packed-bed environments. Our approach employs the unresolved coupling method in STAR-CCM+ (Siemens PLM). We test various filter slot geometries, including straight slots, keystone slots, wire-wrapped screens (WWS), and seamed slots, all under laminar flow conditions. Our findings highlight the significance of gravity, inter-particle forces, and interactions between the filter wall and the particles in multi-particle arch formation at both the slot opening and microscale levels. We confirm that a multi-particle arch can be formed within a specific slot width. Interestingly, while maintaining a constant slot width, we observe that the slot length has an insignificant effect on multi-particle arch formation and stability. In summary, our CFD–DEM model successfully simulates and predicts multi-particle arch formation, stabilization, breakage, and reformation, allowing for comprehensive testing of the effects of various parameters. This research offers valuable insights into a complex phenomenon that is crucial in packed-bed filtration systems. [ABSTRACT FROM AUTHOR]

This research aims to solve the problem of material accumulation on the screen surface of the cleaning device of tracked combine harvester and proposes an innovative solution of designing a pre-screening device based on the traditional cleaning device. The problem of material accumulation on the screen surface is improved, which in turn enhances the cleaning efficiency. In this study, CFD-DEM coupled simulation technology is used to simulate and analyse the cleaning device, and the effects of airflow velocity, vibration frequency and amplitude on the cleaning effect are explored, and the impurity content and loss rate are used as evaluation indexes. Through orthogonal experimental analysis, the optimal parameter combination of the cleaning device was determined as airflow velocity 11 m/s, vibration frequency 9 Hz, amplitude 30 mm, impurity content rate 2.10% and loss rate 1.62%. The experimental results show that increasing the pre-screening device can significantly improve the material separation effect, reduce the loss and improve the cleaning efficiency. [ABSTRACT FROM AUTHOR]

Deep-sea minerals are regarded as the most economically viable and promising mineral resource. Vertical hydraulic lifting represents one of the most promising methods for deep-sea mining lifting systems. To mitigate the potential for clogging due to the aggregation of particles in vertical pipe transport during deep-sea mining operations, this paper employs numerical simulations utilizing the computational fluid dynamics and discrete element method (CFD-DEM) model to investigate the swirling flow transportation of mineral particles. The characteristics of the swirling flow field and the motion law of double-size particles at different swirling ratios are investigated. The findings demonstrate that, in comparison to axial transport within the pipeline, the particle movement observed in swirling flow transport exhibits an upward spiral trajectory. This phenomenon facilitates the orderly movement of particles, thereby enhancing the fluidization of particles within the pipeline. An increase in the swirling ratio (SR) has a considerable impact on the velocity within the pipe. The tangential velocity distribution undergoes a gradual transition from centrosymmetric to non-centrosymmetric as the distance from the inlet increases. An increase in the SR results in an enhanced aggregation of particles at the wall, accompanied by a notable rise in the local particle concentration. The value of SR = 0.3 represents a critical threshold. When SR exceeds this value, the distribution of particles in the cross-section reaches a relatively stable state, rendering it challenging to further alter the distribution and concentration of particles, even if the SR is augmented. Furthermore, the maximum local particle concentration in the vicinity of the wall tends to be stable. These results provide valuable insights into vertical pipe swirling flow transport for deep-sea mining. [ABSTRACT FROM AUTHOR]

In the transportation of grain particles, elbow wear is a pressing concern. A novel approach to mitigate this involves introducing a lateral air supplement rotation mechanism that enables swirling transportation. We assessed the integration of this device at angles of 45°, 55°, and 65° to the central axis of the main pipeline. While the multiphase flow velocity within the main conduit was held constant at 20 m/s, the lateral device's airflow velocities were tested at 20, 30, and 40 m/s. Utilizing the CFD–DEM simulation for grain particle transportation around bends, our findings indicated that an optimal arrangement was with the lateral device at 55° relative to the main pipeline, with an airflow speed of 30 m/s. This setup fostered a forward particle spiral, drastically diminishing wear on the pipe wall. Experimental evaluations corroborated the simulation's outcomes. [ABSTRACT FROM AUTHOR]

After hydraulic fracturing, unconventional reservoirs frequently encounter challenges related to limited effective proppant support distance and suboptimal proppant placement. Due to the strong heterogeneity of offshore reservoirs, which causes varying fracture roughnesses depending on different lithologies, a systematic study of the relationship between roughness and proppant transport could optimize operational parameters. This study incorporates the box dimension method for fractal dimension analysis to quantify roughness in auto-correlated Gaussian distributed surfaces created by true triaxial tests. Combined with the numerical analysis of (computational fluid dynamics) CFD-DEM (discrete element method) for bidirectional coupling, the laws of proppant deposition and transport processes within fractures with different roughnesses are obtained through comparative verification simulations. The results show that for rougher fractures of shale, the proppants are transported farther, but at JRC_52, (joint roughness coefficient), where there may be plugging in curved areas, there is a risk of near-well blockages. Compared to the smooth model, fluctuations in JRC_28 (tight sandstone) drastically increase turbulent kinetic energy within the fracture, altering particle transport dynamics. Moreover, smaller proppants (d/w ≤ 0.3) exhibit better transport capacity due to gravity, but the conductivity of the proppant is limited when the particles are too small. A d/w of 0.4 is recommended to guarantee transport capacity and proppant efficiency near the well. Additionally, proppants injected sequentially from small to large in shale fractures offer optimal propping effects, and can take advantage of the better transport capacity of smaller proppants in rough fractures. The large proppant (d/w = 0.8) is primarily deposited by gravity and forms a sloping sand bed, which subsequently ensures the aperture of the fractures. This research provides a fresh perspective on the influence of fracture roughness on proppant transport in offshore unconventional reservoirs and offers valuable considerations for the order of proppant injection. [ABSTRACT FROM AUTHOR]

Ore collection is very important in deep-sea mining for seafloor massive sulfide (SMS). In view of the characteristics of SMS ores produced by mechanical crushing, which contain coarse particles and a wide particle size distribution, in-depth research on the collection process with a device combining a rotary crushing head and a flat suction mouth was conducted. In this paper, solid–liquid two-phase flow in the hydraulic collection process with a drum rotation is carried out using the computational fluid dynamics-discrete element method (CFD-DEM), and the flow field characteristics and particle motion characteristics are analyzed. The results indicate that particles with a maximum diameter of 20 mm can be effectively collected when the suction velocity is 3 m/s. The collection process of SMS mainly goes through three stages: particle disturbance start-up, partial particle influx, and stable collection. In addition, the appropriate drum speed facilitates the collection of SMS ore. Finally, the correctness of the numerical method was assessed using similarity experiments. This work can be used to guide the design of underwater mining equipment. [ABSTRACT FROM AUTHOR]

Particle distribution, wear failure, and particle passage performance in a two-stage mixed-transported pump are investigated by coupling computational fluid dynamic (CFD) and discrete element method (DEM). Results exhibit good agreement with the experimental data. The velocity and trajectory of a 10 mm particle are examined under three different concentrations. Consequently, the relationship between particle motion and the wear on the impeller and volute is revealed. The results indicate that low-speed particles lead to particle packing at the inlet of the first stage. The force variation of particles is closely related to the number of collisions with the wall. The wear on the suction side of the second-stage impeller and the second-volute wall are significantly less than that on the first-stage. Finally, the particle passage coefficient P is defined, demonstrating that the particle passage performance of the second-stage pump is better than that of the first-stage. [ABSTRACT FROM AUTHOR]

The unstable mechanical behavior of soil particles during suffusion, including migration and clogging of fine particles in porous media, is prone to induce seepage catastrophes. Mechanical behavior of migratory fines and porous soils during suffusion is significantly influenced by the particle shape, which remains unclear. In this study, a coupled computational fluid dynamics and the irregular discrete element method (CFD-iDEM) framework is developed to investigate the migration and clogging mechanisms. A series of numerical simulations that consider spheres and irregular particles with different levels of aspect ratio are carried out to elucidate the microscopic origins of shape effects on clogging. Migratory fine particles are discharged from the grain inlet and enter the coarse particle skeleton by imposing a downward seepage flow. The subsequent migration and clogging phenomena and microscopic mechanisms are investigated. The results reveal that irregular particles present varying degrees of ability to develop clogging clusters, and spheres are more prone to traverse deeper into soil skeleton. The proposed CFD-iDEM method is able to reproduce macroscopic phenomena of saturated porous medium as well as to analyze microscopic origins of fluid–particle interactions, which contributes to practical guidance for engineering applications. [ABSTRACT FROM AUTHOR]

Radial well filled with phase change material has been proposed as a novel sand control method for hydrate exploitation. In order to reveal the sand control mechanism, CFD-DEM coupling method is applied to simulate the migration, settlement, and blockage processes of sand particles in the radial well. The obtained results indicate that three scenarios have been recognized for sand particles passing through sand control medium, based on the diameter ratio of sand control medium to sand particle (Dd): fully passing (Dd = 8.75-22.5), partially passing and partially blocked (Dd = 3.18-5.63), and completely blocked (Dd = 2.18-3.21). After being captured by the sand control medium, sand particles can block pores, which increases fluid flow resistance and causes a certain pressure difference in the radial well. The pressure in the radial well should be lower than the hydrate phase equilibrium pressure during sand control design, for the purpose of promoting hydrate decomposition, and sand capture. The length of the radial well should be optimized based on the reservoir pore pressure, production pressure difference, bottom hole pressure, and the pressure gradient in the radial well. It should be noticed that the sand control medium leads to a decrease in permeability after sand particles captured. Even the permeability is reduced to several hundred millidarcy, it is still sufficient to ensure the effective flow of gas and water after hydrate decomposition. Increasing fluid velocity reduces the blocking capacity of the sand control medium, mainly because of deterioration in bridging between sand particles. [ABSTRACT FROM AUTHOR]

As a common industrial valve solution in slurry pipeline systems, Y-type slurry valves must be designed with properly shaped valve seat sealing rings to alleviate particle erosion and keep the valve operating in optimal condition. In this study, we investigate four different valve seat shapes with varying inner angles to understand the effect of the seat structure on particle erosion in Y-type slurry valves. We conducted computation fluid dynamics discrete element method simulations to analyze the impact of different valve seat shapes on the characteristics of particle-liquid two-phase flows and erosion. We also performed a detailed analysis of velocity and pressure distributions for liquid phase and particle velocity distributions as well as surface erosion on key valve components. We observed the primary erosion areas to be the back surface of the valve body, the inner surface of the valve seat, and the front surface of the valve disc, and as a result, we investigated the erosion distribution in these areas with different valve seat structures. Our simulation results indicate that the variation in particle diameter and the inner angle of the valve seat sealing ring have significant impacts on erosion in the studied areas. [ABSTRACT FROM AUTHOR]