Simulation Of Particulate Flows Research Articles

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

Experiment and particle flow simulation of unloading induced shearing properties for jointed sandstone materials

Shear tests on sandstone containing non-connected joints under the unloading normal stress but fixed shear stress conditions were conducted with various initial normal stress and unloading rate. During the unloading process, continuous shear dilation could be observed. For initial normal stress = 5–20 MPa, the sliding initiation normal displacement decreased by 17.14–66.32 % but the sliding initiation shear displacement increased by 21.91–98.19 %. The sliding initiation normal stress declined by 7.18–15.57 % for unloading rate = 0.002–0.01 MPa/s but increased by a factor of 3.18–3.53 with the initial normal stress. Shear sliding of the jointed samples was more prone to occur at a smaller initial normal stress with a larger unloading rate. From the numerical simulation results via PFC2D, during the unloading process, cracking was first initiated from central part of the rock bridge and propagated gradually to coalesce with cracks developed from the joint tips. The penetrating fracture surfaces led to shear sliding of the jointed samples, and shear wear occurred on the fractures as shear displacement continued increasing. For unloading rate = 0.002–20 MPa/s, quantity of cracks corresponding to shear displacement of 1.2 mm decreased by 12.18–36.34 %. Cracking degree was more serious for the samples at a low unloading rate due to progressively developed cracks near the main failure planes before shear sliding and more accumulated cracks in the shearing wear stage for fractures under a larger normal stress.

The study of the separation and deposition of dredging soil slurry under physical disturbance.

Most existing research uses experimental designs for testing, which cannot efficiently analyse the migration and sorting rules of particles in the disturbed slurry. Therefore, based on the fluidized bed flow film theory, a slurry flow film structure system is established according to the disturbance state of the fluid. On this basis, the particle size and distribution law of the disturbing force formed by slurry disturbance are analyzed, and the calculation model of single particle lift in the flowing film is also analyzed. On this basis, using Markov probability model, the probability of particle lifting and sorting between layers is theoretically deduced. Then, according to the particle ratio of the original mud, the settlement gradation of the particles in the disturbance is analyzed. It can also predict the separation degree of particle in natural turbulence, fluidized beds, and sludge mechanical dewatering. Finally, according to the particle flow software PFC (Particle Flow Code), the main influencing parameters (disturbing force and gradation) were verified and analyzed. The results show that the particle flow simulation results are in good agreement with the calculation results. The model of slurry membrane separation proposed in this paper can provide a basis for studying the mechanism of slurry disturbance separation and particle deposition.

Macroscopic Mechanical Properties of Brittle Materials with a 3D Internal Crack Based on Particle Flow Simulations

Pre-existing cracks significantly influence the macro-mechanical properties of rock. The macro-mechanical properties and crack propagation process of brittle materials with a 3D internal crack were investigated with PFC3D simulation in this paper. To determine the micro-parameters, the influence of micro-parameters on the macro-mechanical properties and ultimate failure mode was discussed. SJM’s parameters had little influence on the macro-mechanical properties and ultimate failure mode. Peak axial stress was changed greatly by strength parameters and friction coefficient, and the macro-elastic modulus was influenced greatly by Young’s modulus and changed slightly with other parameters. The failure mode changed gradually with all micro-parameters except Young’s modulus, which had a strong but irregular impact on it. The peak stress was 138 MPa in the simulation of the sample with a 3D internal crack, which agreed well with the experimental result (137 MPa). The crack propagation process can be divided into three stages: 17% of total crack was generated in the initial stage; 76% of the total crack was propagated when main failure surface coalesced; finally, the failure surface expanded downwards and caused the sample to be destroyed. Cracks initially appeared near the end of the lower major axis of the internal crack, which was in agreement with experimental results. The results demonstrated that PFC3D is a reliable method to simulate the failure process of brittle materials with internal cracks.

Simulation of non-spherical particles in curved microfluidic channels

The paper analyzes the migration of non-spherical particles in curved micro-channels. Inertial migration combined with Dean drag results in a reduced set of stable focusing positions in specific regions of the cross section of the channel. These are studied using fully resolved transient simulations of particulate flows in rectangular curved ducts with oblate and prolate particles at a bulk Reynolds number of 100 and dilute particle concentrations. The simulations were conducted with four particles in a periodic domain, instead of only one, as common practice, to investigate the particle interaction. It is observed that the focusing positions are different for the non-spherical particles compared to those obtained with spherical ones. Not only non-spherical particles focus closer to the upper and lower walls, but also their focusing position is closer to the half width of the channel. Furthermore, the migration velocity along the cross section is compared between particle shapes. Results show that all shapes lead to a significant change in migration velocity between outer and inner halves of the channel. This effect is substantially more pronounced for non-spherical particles and is observed for the first time here. It offers an independent possibility for particle separation according to shape.

Multiscale mechanical characterizations of ultrafine tailings mixed with incineration slag

Adding a type of municipal solid waste (incinerator slag) into ultrafine tailings can effectively enhance the mechanical properties of tailings. With an aim to study the macro- and micro-mechanical properties of the tailings slag mixture (TSM), the strength parameters (internal friction angle, cohesion) and micro-mechanical properties with different slag contents were analyzed by geotechnical experiments and particle flow simulations, respectively. The macroscale experimental results demonstrated that the strength parameters of TSM were much higher than that of tailings. Strength parameters also showed non-linear-rising trends with increasing slag content. For the slag content of 40%, the maximum cohesiveness of TSM was determined at 65.2 kPa, and the corresponding friction angle was 39.9°C. Furthermore, the Particle Flow Code (PFC) micro-simulation software was used to analyze the micro-mechanical characteristics of the TSM at different slag contents. The microscale simulation outcomes indicated that the particle transport, particularly in their moving directions, became increasingly chaotic with an increase in the slag content; also, the slag particles significantly impacted the shear processing zone of the TSM. These experimental and numerical results brought more scientific insights into the shear failure mechanism of TSM.

Precursory Analysis of Water-Bearing Rock Fracture Based on The Proportion of Dissipated Energy

In order to better understand the failure process of water-bearing rocks, samples of water-bearing sandstone were tested uniaxially. The failure process and the development of internal cracks were studied through the evolution characteristics of dissipated strain energy and particle flow simulation. In this study, we found that: (1) The presence of water in sandstone results in a reduction in energy storage capacity as well as strength. (2) The dissipated energy ratio curve of sandstone samples and simulated samples’ internal fracture development curve has obvious stages. The dissipated energy ratio turning point and the rapid fracture development point are defined as the failure precursor points of sandstone samples and simulated samples, respectively. In both sandstone samples and simulated samples, the ratio between failure precursor stress and peak strength remains almost unchanged under various water conditions. (3) The ratio of fracture to dissipated energy (RFDE) of sandstone is proposed, and interpreted as the increased number of cracks in the rock under the unit dissipated. On this basis, the fracture initiation dissipated energy (FIDE) of sandstone under different water cut conditions is determined, that is, the dissipation threshold corresponding to the start of the development of sandstone internal cracks. (4) The analysis shows that RFDE increases exponentially and FIDE decreases negatively with the scale-up in moisture content. Further, high moisture content sandstone consumes the same dissipative strain energy, which will lead to more fractures in its interior. The research in this paper can lay a theoretical and experimental foundation for monitoring and early warning of rock engineering disasters such as coal mining, tunnel excavation, slope sliding, and instability.

Inertial migration of non-spherical particles in straight microfluidic channels

The paper reports on simulations of particulate flows in square ducts with oblate and prolate particles at a bulk Reynolds number of 100 and dilute particle concentration. Inertial migration leads to focusing of particles in specific regions of the cross section. It is observed that these positions are different for the non-spherical particles compared to those obtained with spherical ones. Prolate particles exhibit Jeffery-type orbits, while oblate particles rotate around their axis of symmetry. As a result, the rotation-induced migration of prolates is much slower than for spheres and oblates. An analysis of the surrounding flow is used to show differences in the velocity field. In a second set of simulations, the particle concentration was increased by a factor of 4 with the same domain size, so that neighboring particles influence each other. The duration until focusing is achieved is substantially increased. The focusing position moves slightly to the wall, and further effects are generated. Steady particle oscillations in position are seen for spheres, and the formation of particle trains is observed in all cases. The interaction of prolate particles is particularly complex and addressed in substantial detail.

High-resolution model of complexly shaped bodies motion using an IBM-VOF-DEM coupling method

A new coupling model that focuses on the simulation of gas-liquid flow and irregular-shaped particulate flows was proposed based on the coupling of FD/IBM, VOF and DEM. A wide range of computing cases was presented for validation, including the spherical and cylindrical particle settling in fluid, where the particle Reynold's number is small, and the vortex shedding phenomenon could still be captured. Further, the simulations that the wooden blocks float upward and the cones fall into the water at a high Reynolds number were constructed. All these simulating results keep well consistent with the experiments. It turns out that the model is reliable for simulating the particulate flows as Reynold's number is up to 420,000. Besides, the model shows great strength of the solid-fluid motions capture capability, especially for the irregular-shaped objects moving trajectories at different scales from 0.00167 to 0.3 m, which is potentially helpful in industrial engineering. • A fully rsolved IB-VOF-DEM model is developed. • Typical and multi-scaling validating simulations are presented. • The model covers a wide range of Reynolds number from 400 to 420,000. • Multi-sphere model and Monte-Carlo method are employed.

Developing mucociliary clearance model for the numerical simulation of two-way coupling particulate flow inside the nasal cavity in the presence of deep breathing

Generally, it is essential to investigate mucociliary clearance as a defensive mechanism for drug delivery through the respiratory tract system. However, regarding the vicinity of micro-macro scales inside the respiratory system, typically, it has been neglected in numerical simulations. Hence, in the current research, a new boundary condition is developed to consider the effects of mucociliary clearance on deposited particles inside the nasal cavity. The two main components in developing the mucociliary clearance model are, namely, the cilia metachronal wave and wall-adjacent cell information. The cilia metachronal wave and wall-adjacent cell velocity generally determine the velocity and direction of the mucociliary clearance model, respectively. Therefore, the new boundary condition does not create an extra computational cost. Accordingly, all developing procedures are performed using the open-source toolbox (OpenFOAM 7). Herein, by applying the new boundary condition to the nasal wall, it is observed that each deposited particle is trapped and followed a different path alongside the nasal wall. Moreover, the initial deposition location of particles is changed up to 3% by means of the new implemented boundary condition based on the particle aerodynamic diameter. Based on the results, tracking of particles for 5 min indicated that 42% of deposited particles inside the nasal valve are transferred to the main airway. This means that drug absorption locations change with the consideration of the mucociliary clearance model. The results reveal that such a simplified strategy to account for mucociliary clearance can contribute to the prediction accuracy of the transport of sprayed therapeutic drug particles through the nasal cavity.

Numerical Simulation of the Microscopic Plugging Mechanism and Particle Flow Process of the Microsphere System.

The microsphere system has small initial particle size, excellent swelling performance, simple manufacturing process, and strong plugging ability. It has great application potential in the field of plugging and profile control of deep reservoirs. Microspheres can effectively plug the pores of fractured cores, inhibit the rapid breakthrough process, and improve the sweep efficiency of the injected fluids. However, the microscopic plugging mechanism of microspheres on fractured cores is still unclear. In this study, the distribution of microspheres after plugging was observed through specially prepared core models. Furthermore, the microscopic plugging mechanism of microspheres in fractured reservoir cores was clarified, including direct microsphere plugging, cluster bridging plugging, adhesion plugging, extrusion-deformation plugging, and extrusion-crushing plugging. Then, particle flow simulation software was used to establish the fluid-solid coupling model of microsphere plugging, and then, the numerical simulation of the plugging process was realized by Python module programming. Through this study, the plugging effect of microspheres under different fracture opening conditions was clarified. Moreover, the effects of injection pressure difference, fracture width, and particle size ratio on the fluid-solid structures of microsphere plugging were analyzed. The results show that the smaller the particle size ratio, the greater the injection pressure difference, the fracture width, and the reduction magnitudes in fracture porosity and core permeability and the higher the plugging rate. The numerical simulation results well support the microsphere plugging mechanism obtained by experiments. The results of this study can provide theoretical and technical support for the development of deep profile control and flooding and enhanced oil recovery technology of the polymer microsphere dispersion system in fractured low-permeability reservoirs.

A review of salt precipitation during CO2 injection into saline aquifers and its potential impact on carbon sequestration projects in China

The injectivity of saline aquifers is one of the most important factors affecting CO2 geological storage. However, CO2 injection fields showed that a lot of crystallized salt precipitates out of the high-salinity water due to the water evaporation caused by dry CO2 injection, reducing the CO2 injection rate. It is still difficult to predict the distribution of precipitated salt and its effect on the porosity and permeability near the wellbore. Therefore, the process of water flow, water evaporation, salt crystallization, salt migration, and salt retention during CO2 injection into saline aquifer are reviewed in detail to analyze the key factors for accurately predicting the distribution and amount of precipitated salt. The analysis shows that the salt crystallization kinetics and precipitated salt dynamic migration are two key factors in revealing the mechanism of reservoir impairment caused by salt precipitation. To analyze salt crystallization kinetics, a lab-on-chip experiment must be developed to capture and quantify the salt crystallization under high temperature and pressure. To analyze salt dynamic migration, the CO2 flooding experiment, 3-D CT imaging, and particle flow simulation need to be analyzed to understand the dynamic migration and accumulation of precipitated salt during CO2 injection in combination. A new comprehensive simulation method that can consider these key processes is also needed to be developed to analyze the salt precipitation distribution and its influence on CO2 injectivity on a field scale. When CO2 is injected into low porosity and permeability saline aquifers in China, hydraulic fracturing can be adopted to improve injectivity, but multi-layer commingled CO2 injection should be avoided because a severe reservoir impairment caused by salt precipitation can occur even under low salinity.