Simulation Of Particulate Flows Research Articles

Particle Flow Simulation Study of Damage Evolution in Expansive Slurry–Fractured Rock Mass Composites under Direct Shear Conditions

Particle Flow Simulation Study of Damage Evolution in Expansive Slurry–Fractured Rock Mass Composites under Direct Shear Conditions

Investigation of the Shear Mechanism at Sand-Concrete Interface under the Influence of the Concave Groove Angle of the Contact Surface

A “random-type” sand–concrete interface shear test was developed based on the sand cone method, with a focus on the most commonly encountered triangular contact surface morphology. A “regular-type” triangular interface, matched in roughness to the “random-type”, was meticulously designed. This “regular-type” interface features five distinct triangular groove inclinations: 18°, 33°, 50°, 70°, and 90°. A series of sand–concrete interface direct shear tests were conducted under consistent compaction conditions to investigate the impact of varying compaction densities and triangular groove inclinations on the shear strength at the interface. Particle flow simulations were utilized to examine the morphology of the shear band and the characteristics of particle migration influenced by the triangular contact surface. This analysis is aimed at elucidating the influence of the inclination of the triangular groove on the shear failure mechanism at the sand–concrete interface. The findings indicate that: (1) The morphology of the interface significantly impacts the shear strength of the sand–concrete interface, while the shape of the stress-displacement curve experiences minimal alteration. (2) At smaller inclination angles, particle contact forces are arranged in a wave-like configuration around the sawtooth tip, resulting in a non-uniform stress distribution along the sawtooth slope. However, as the inclination angle grows, the stress concentration at the sawtooth tip diminishes, and the stress distribution across the sawtooth slope becomes more consistent. (3) Particle migration is significantly influenced by the sawtooth’s inclination angle. At lower angles, particles climb the structure’s tip through sliding and rolling. As the angle increases, particle motion shifts to shear, accompanied by a transition in friction from surface friction to internal shear friction. This leads to the formation of a wider shear band and an increase in shear strength.

Experimental study on failure mode and fracture evolution characteristics of red shale in Kaiyang Phosphorus mining area

In order to study the failure mode and fracture evolution characteristics of red shale in Kaiyang Phosphorus mining area, conventional triaxial compression mechanical tests of red shale with different bedding dip angles were carried out by using DSTD-1000 electro-hydraulic servo rock mechanics experiment system. Based on the laboratory test results, the conventional triaxial particle flow simulation of red shale samples with different bedding dip angles was carried out using discrete element PFC2D. The results show that: (1) the failure mode of red shale is controlled by bedrock when the bedding dip angle is 0° and 60° ~ 90°. When the bedding dip angle is 15° ~ 45°, the rock failure mode is controlled by bedding. The compressive strength of rock is the minimum when the bedding dip angle is 30°and the maximum at 0°, which is about 2 times of the minimum. (2) In the failure process of red shale, the cracks with different bedding dip angles show slow growth stage, accelerated growth stage and stable stage with axial strain. The whole failure process is dominated by tensile cracks, accompanied by a few shear cracks. (3) The type of displacement field varies with the bedding dip angle: tensile failure and shear failure are the main displacement field types at 15° ~ 45°, and mixed failure is often the main mode at 60° ~ 90°and 0°. The research results provide the basis and reference for the safety control of red shale roadway.

Migration trajectories and blocking effect of the fine particles in porous media based on particle flow simulation

The particle flow code method based on the discrete element method was used to establish the seepage migration model of fine particles [fine particles (FPs), i.e., suspended particles] in a porous medium. A series of numerical simulations were carried out by changing the particle size, seepage velocity, particle injection number, and wide particle size gradation. The research showed that large FPs play a major role in blocking porous medium channels when the injected FPs have a wide size gradation. Due to the blocking effect, small FPs that would not otherwise have deposited also deposit. Moreover, by increasing the number of large FPs in the mixed particles, the total number of particles deposited and the number of smaller FPs deposited will also increase. The distribution of FPs in porous mediums can be divided into three types: surface deposition, internal deposition, and non-deposition. When the seepage velocity increases and reaches a seepage threshold, which is the critical seepage velocity, the deposited FPs will once again be in a suspended state and undergo migration. On the contrary, the FPs will continue to maintain their sedimentary state, and the critical seepage velocity will also increase correspondingly with increasing particle size.

Lattice Boltzmann method for particulate multiphase flow system

This study proposes a numerical model for particulate three-phase flow in microchannels based on multiphase lattice Boltzmann method (LBM). The model combines the color-gradient method to track the immiscible fluid-fluid interface and the two-fluid model (TFM) to describe particle-particle and particle-fluid interactions, which can efficiently simulate transport and displacement processes involving large amounts of particles. A mixture-rheology TFM algorithm is proposed by introducing a mixture phase with rheology properties obtained from experiments instead of the conventional TFM particle phase with artificial viscosity models. Multi-relaxation-time (MRT) collision operator and GPU computing are adopted to enhance the numerical stability and efficiency. Various theoretical benchmarks for particle transport and two-phase flow are performed respectively to verify the accuracy of the proposed model. Exceptional consistency between results from particulate three-phase flow simulation and microfluidic experiments further confirms the reliability of our model, especially in capturing the inertial lagging and accumulation phenomena under multiphase and porous flow conditions. The proposed numerical framework will benefit our understanding of multiphase displacement with microgels in microchannels with complex geometries.

A novel particle decomposition scheme to improve parallel performance of fully resolved particulate flow simulations

This study addresses the challenge of simulating realistic particle systems by proposing a novel particle decomposition scheme that improves the parallel performance of surface resolved particle simulations. Realistic particle systems often involve large numbers of particles and complex particle shapes. The resulting need to account for shape factors requires the inclusion of even more particles to obtain statistically meaningful results. However, the computational cost increases with the number of particles, making efficient parallelization crucial. Therefore, the proposed scheme aims to improve the scalability by optimizing the communication and data management between processors. Through hindered settling experiments, the applicability and performance of the novel particle decomposition scheme are thoroughly investigated using the homogenized lattice Boltzmann method. The results show that the proposed method significantly improves the performance, especially in scenarios with a large number of particles, by reducing communication constraints and improving scalability. This research contributes to the advancement of computational methods for efficient study of complex particle systems and provides valuable insights for future developments in this field.

Step-path failure mechanism and stability analysis of water-bearing rock slopes based on particle flow simulation

Step-path failure is a typical damage mode of rock slope featuring intermittent joints. In order to investigate the effect of water-fracture interaction on the stepped failure, laboratory experiments of rock materials and numerical simulation of slopes with intermittent joints were conducted. At the laboratory scale, the influence of water-fracture interaction on the mechanical characteristics and acoustic emission response of step-path failure in rocks was examined, and the particle flow model parameters were calibrated for uniaxial testing. At the field scale, the step-path failure process of the rock slope near Longmenqiao reservoir was numerically analyzed using the particle flow method to assess the effects of water and joint distribution on failure. Laboratory findings suggest that compared with dry red sandstone, the average uniaxial compressive strength and average elastic modulus of saturated red sandstone decrease by 35.82% and 23.33%, respectively. The increase in fissure angle in sandstone results in enhanced strength and stiffness, alongside a transition from shear to tension failure mode, with a delayed occurrence of large-scale acoustic emission events. In particular, within the 30°–60° range, the uniaxial compressive strength and elastic modulus of saturated sandstone increase by 66.78% and 29.64%, respectively. The analysis of crack propagation and stress field during slope deformation shows that step-path failure is a progressive process from bottom to top, and revealed the control mechanism of joint and bridge angle on slope stability. The research results enhance the understanding of the step-path failure mechanism and provide important theoretical support for the stability evaluation and landslide monitoring of rock slopes with intermittent joints.

Particle Flow Simulation of Sand Loss through Cracks in Segmental Linings

Particle Flow Simulation of Sand Loss through Cracks in Segmental Linings

Numerical simulation of particle flow around the impulsive monopile

In order to explore the particle flow field characteristics around the impulsive monopile, the particle flow field and particle distribution around impulsive monopile were simulated based on the classical impulsive flow around a monopile at medium and low Reynolds number (Re = 550). The Large Eddy Simulation (LES) technique was harnessed to capture the dynamic flow field around the monopile and to facilitate in-depth analysis of vortex evolution. Concurrently, the Lagrangian approach was employed to track and characterize particle trajectories, shedding light on the patterns of particle diffusion and congregation in the vicinity of the monopile under varying Reynolds numbers. Additionally, this investigation unveils the distinctive behavior of particle flow during the impulsive starting and stopping phases adjacent to the monopile. Leveraging these insights, the study elucidates the intricate influence of the unsteady flow field dynamics around the monopile on the progression of particle flow.

Discrete element simulation of particle flow and separation in a vibrating screen with variable rectangular hole screen

The screening operations aim to achieve large processing capacity and high screening accuracy. However, there is a certain inherent contradiction between these two goals. This paper proposes a variable rectangular hole screen for the negative pressure vibrating screen. Through numerical simulation of variable rectangular hole screens with different length-side ratios, the optimal ratio of adjacent rectangular holes is determined to be 60:37. This innovative screen addresses the limitations of traditional screening operations, effectively improving the processing capacity of drilling fluids. It achieves a high screening accuracy while reducing the adverse effects of screen paste and screen clogging on drilling fluid sieve penetration. The study also investigates the effects of amplitude, vibration frequency, feed rate, and screen transportation speed on particle behavior through the screen. These findings serve as a theoretical basis for optimizing the vibration parameters and working condition parameters of the negative pressure vibrating screen.

Study on the mechanical properties of sandstone-shale composite continental shale gas based on the discrete element method

China has abundant continental shale oil resources, and multiple shale oil exploration and development demonstration zones have been established, making it a key field for oil and gas exploration and development. However, drilling and fracturing treatment often encounter vertically interlaced and superimposed sandstone and shale reservoirs, which significantly affect the stability of the reservoir and the propagation of fractures. Therefore, it is of great significance to study the rock mechanics characteristics of sandstone-shale composite. Using the orthogonal experimental method for microscale parameter calibration, this study established the relationship between the macroscopic and microscopic parameters of sandstone-shale in the parallel bond model. The results of the orthogonal experimental scheme were analyzed using multi-factor variance analysis and linear regression analysis to determine the influence and ranking of each microscale parameter on the macroscopic parameters. Based on the results of uniaxial and triaxial compression experiments, the particle flow simulation of sandstone-shale composite rock samples was studied using the discrete element method. The study investigated the influence of the thickness ratio, combination form, and confining pressure of sandstone-shale on the mechanical properties of composite rock samples. The results showed that: (1) Under uniaxial loading conditions, for the combination form of sandstone on top and shale on the bottom (M-S type), the peak stress of the composite rock sample increased first and then decreased and then increased again with the increase of the thickness of sandstone; for the combination form of shale on top and sandstone on the bottom (S-M type), the peak stress of the composite sample decreased first and then increased and then decreased again with the increase of the thickness of shale. (2) After applying confining pressure, the compressive strength of the M-S type composite sample decreased with the increase of the thickness ratio of sandstone, while the compressive strength of the S-M type composite sample increased with the increase of the thickness ratio of shale as well as the compressive strength of the composite sample was lower than that of any complete rock sample. (3) Under uniaxial loading, the fracture mode of the composite sample was related to the combination form and the thickness ratio of different lithologies. For the M-S type sample, when the thickness ratio of sandstone was <30%, the sample was mainly fractured by tension, and when the thickness ratio of sandstone was >30%, it was mainly fractured by shear mode. For the S-M type sample, when the thickness ratio of shale was <70%, the sample had the most internal shear cracks, and when the thickness ratio of shale was >70%, it had the most tension cracks.

Calculation of particle volume fraction in computational fluid dynamics-discrete element method simulation of particulate flows with coarse particles

Computational fluid dynamics-discrete element method is frequently used for modeling particulate flows due to its high efficiency and satisfactory accuracy. The particle volume fraction is a crucial parameter that significantly affects the computation accuracy. It may be extremely large when the particulate flows contain coarse particles because it is determined by the ratio of particle volume to cell volume. In this paper, the performance of different methods, such as the divided particle volume method (DPVM), the big particle method, and the diffusion-based method, for computing the particle volume fraction is thoroughly reviewed, implemented, and investigated. It turns out that the DPVM must not be used when the particle size is larger than cell size due to significant fluctuation of the particle volume fraction field. The big particle method is optimized for simulation accuracy and code implementation. The optimized big particle method is similar to the diffusion-based method by diffusing the particle effects to the surrounding cells. It demonstrates greater consistency with experimental observations compared to the diffusion-based method, primarily attributed to its incorporation of polydisperse effects.

Erosion Life Prediction of Metal Mesh Screen Pipes in Oil Wells Based on Numerical Simulation of Discrete Particle Flow.

High-speed fluid-carried sand particles pose a significant challenge to oil well screen pipes, leading to sand control failure and adversely affecting the well's production and recovery rates. This research targets the commonly used metal mesh screen pipe in oil well sand production and establishes a full-sized three-dimensional structure model. A fluid-solid coupling of discrete particle flow numerical simulation algorithm is incorporated to formulate a novel method for predicting the screen pipe's erosion life. This method provides a solution to the complex task of predicting the pipe's lifespan under oil sand fluid erosion. The analysis elucidates the impact of sand particles on the velocity distribution and erosion rate of the metal mesh at varying velocities, facilitating the prediction of the mesh screen pipe's erosion life. Key findings reveal that the velocity and erosion rate vary across the different layers. The first layer screen experiences velocity and erosion rates that are 3.6-3.76 times and 2.45-2.50 times, respectively, higher than those at the inlet. The second layer screen undergoes velocity and erosion rates 2.32-2.43 times and 1.04-1.06 times, respectively, higher than those at the inlet. Erosion failure primarily occurs in the first layer screen due to velocity expansion instigated by the screen tube's structure. The discrete flow numerical simulation method proves valuable in predicting the mesh screen's erosion life at different flow rates, with a maximum error of 6.38% when compared with field monitoring life values. This method introduces a new technical approach to predicting the life span of metal mesh screens in oil wells. The study concludes by suggesting measures to extend the screen pipe's lifespan, thereby enhancing oil recovery.

Experiment and particle flow simulation on mechanical properties and crack evolution mechanism of Brazilian discs containing two flaws

Abstract The mechanical behavior of fractured rock in tensile stress environment is a hot topic in underground mining engineering. Here, real surrounding rock of coal mine roadway was simulated by using rock-like materials and the tensile failure behavior of Brazilian discs with intermittent double fissures was investigated experimentally. The deformation response, fracture evolution, and failure mode of rock were analyzed. The fissured disc specimen's discrete element model was proposed in particle flow code (PFC2D). The microforce field, crack, and energy evolution processes of model specimens were discussed. The results showed that the load-displacement curves exhibit single-peak and double-peak types, corresponding to the splitting penetration and wing crack penetration damage modes of the specimen. The fissure angle or rock bridge angle showed a great influence on the evolution of main cracks and secondary cracks. The double-fissured Brazilian disc failed due to the initiation and transfer of microcracks in the stress concentration zone, combined with the continuous propagation and convergence of those microcracks. The splitting failure of the Brazilian disc is a continuous process of strain energy accumulation from the early stage of loading and instantaneous release of strain energy after obtaining the peak strength as the dissipative energy sharply rises.

Strength, deformation and failure behavior of bolted rock-like specimen with multiple cracks under uniaxial compression by particle flow simulation

Strength, deformation and failure behavior of bolted rock-like specimen with multiple cracks under uniaxial compression by particle flow simulation

Simulation and verification of particle flow with an elastic collision by the immersed edge-based smoothed finite element method

The immersed edge-based smoothed finite element method (IES-FEM) is proposed for the study of elastic collision particulate flow. Particle collision becomes more realistic by using the penalty function and the hyperelastic constitutive model. The effects of grid resolution and Reynolds numbers on particle terminal velocity and drag coefficient are discussed to verify the calculation accuracy and stability. Single-particle collisions with the bottom and side walls are analyzed and experimentally verified. Results show that the calculation error of IES-FEM is less than 0.6% when the fluid grid size is 0.5 times the particle mesh size and the time step is 10–4 s. Particle drag coefficient and flow characteristics agree well with the published models and experiment results. To demonstrate the capabilities of IES-FEM in complex elastic particle systems, the collision and rebound of multiple particles are determined, including the drafting–kissing–tumbling of two circular particles; the chase, collision, and deformation of rectangular particles; and the repeated formation and separation of particle clusters. This work extends the application of IES-FEM in particle-resolved direct numerical simulation methods, which will provide an optional tool for future elastic blood cell flow and collision.

Eulerian–Eulerian RSTM-PDF Modeling of Turbulent Particulate Flow

A novel 3D computational model was developed for the turbulent particulate two-phase flow simulation in the rectangular channel. The model is based on the Eulerian approach applied to 3D Reynolds-averaged Navier–Stokes modeling and statistical Probability Distribution Function method. The uniqueness of the method lies in the direct calculation of normal and transverse components of the Reynolds stresses for both gas and particles. Two cases were examined: a conventional channel flow and grid-generated turbulence flow. The obtained numerical results have been verified and validated by the experimental data, received from the turbulent particle dispersion test. The computed values of the particles’ turbulent dispersion and the maximum value of the particulate concentration distribution show good agreement with the experimental results. The examples are ranged from coal and other bulk material pneumatic transport, vertical fluidized beds, coal gasifiers, and chemical reactors.

A spheropolyhedral-based discrete element lattice Boltzmann method for simulation of non-spherical adhesive particulate flow

Non-spherical particulate flow is commonly encountered in nature, industry and our daily life. But up to now, there still lack effective model to describe the adhesive elastic collision between non-spherical microparticles. To solve this problem, a spheropolyhedral-based discrete element method (DEM) combined with Johnson-Kendall-Roberts (JKR) model is proposed. The contact between non-spherical particles is attributed to the contacts between three geometry features, including vertice-vertice (V-V), vertice-edge(V-E), vertice-face (V-F) and edge-edge (E-E). The JKR adhesive model is modified to calculate the contact force of the contacting geometry features based on the actual contact area. Meanwhile, the lattice Boltzmann coupled with the immersed moving boundary (LB-IMB) method is employed to simulate the fluid flow and fluid-particle interaction. The novel spheropolyhedral-based DE-LBM is verified to be accurate and effective by several experiments and the data in references. Finally, an application test for simulating the packing process of non-spherical microparticles is presented. The method well predicts the packing structure of both adhesive and non-adhesive non-spherical particles, meaning that it can be easily extended to simulate the massive non-spherical microparticles with high effectiveness and efficiency. Program summaryProgram Title: adhesive contact force model for non-spherical particleCPC Library link to program files:https://doi.org/10.17632/vswvv7ppz2.1Developer's repository link:https://github.com/QIAN-C/adhesive-force-model-for-non-sphericalLicensing provisions: GNU General Public License v3Programming language: C++Nature of problem: Various methods have been proposed to handle the complex shapes of non-spherical particles in the discrete element method. However, there is still a lack of effective models for calculating the contact force between the non-spherical fine particles, particularly the adhesive forces.Solution method: Based on the sphere-polygon algorithm and the JKR model, this program has developed a contact force model that can accurately calculate adhesive forces between non-spherical fine particles within the framework of the open source library MechSys (URL: http://mechsys.nongnu.org/index.shtml).

Particle flow simulation of Brazilian splitting failure characteristics of layered shale

Shale reservoir is the research hotspot in the development of unconventional oil and gas resources. The properties of bedding plane have an important influence on the mechanical behavior of shale. According to the fracture characteristics of layered shale under Brazilian splitting load, the effects of bedding angle, bond strength ratio and natural fractures on the tensile strength and fracture pattern of layered shale in Brazilian splitting test were studied by particle flow code. The evolution mechanism of meso–macro fracture of shale is analyzed by combining the dynamic change process of particle mesoscopic force chain and crack. The results show that three types of fracture patterns are observed: splitting tensile failure of shale matrix, splitting tensile failure along bedding plane and tensile–shear composite failure along shale matrix and bedding plane. Mesoscopic cracks initiate at the top and bottom loading points of the disk. After the peak load, mesoscopic cracks propagate through and appear dense force chains until macroscopic failure occurs. The bond strength ratio of bedding plane affects the failure pattern and peak strength of the specimen. With the increase in bedding angle, the tensile strength decreases gradually. Considering the influence of natural fractures, the tensile strength of shale is lower, and the crack propagation is more complex. The research model and results provide theoretical basis for the mechanical properties evaluation and fracture pattern analysis of shale.

Large eddy simulation of flow field and particle dispersion in a ventilated model room using a parallel lattice Boltzmann method

The present paper addresses the use of a parallel lattice Boltzmann solver for large eddy simulation of particulate matter flow in a single ventilated model room. The formulation of lattice Boltzmann method (LBM), implementation of large eddy simulation (LES), description of finite volume method (FVM) and then integration of Lagrangian particle tracking in the present algorithm are outlined. A parallel processing method, known as decomposed domain method, for flow and particle phases is defined. Combined stream and collision step technique is employed to reduce CPU runtime and memory usage. The ultimate objective is validation and comparison of prediction accuracy and speed up between present LBM-LES results, FVM-LES results based on Navier–Stokes equations, and available experimental data. Results of flow field show acceptable accuracy for the present LBM-LES method when using high-resolution lattices. It is revealed that in order to achieve an accuracy almost equal to FVM, LBM requires twice the number of lattices but still provides a higher speed. Also, it is shown that the present model is well capable of predicting vortex core and vortex lines and it can capture the features and structure of the turbulence flow field reasonably well. In the particle field, it can capture concentration patterns and particle dispersion with an admissible discrepancy. The use of presently developed algorithm dramatically reduces computational time, such that speed can increase by up to four times in flow and eight times in particle simulations.Copyright © 2023 American Association for Aerosol Research