Migration Behavior Of Particles Research Articles

Dispersion of reinforcing micro-particles in the laser welding of metal matrix composites: High-fidelity modeling with experimental characterization

Understanding the interaction mechanism between keyhole, solid phase (ceramic particles), and liquid phase (metal matrix) will offer key insights into laser welding/additive preparation of high-performance metal matrix composites. The laminar SiC particle–reinforced Al matrix composite, which is extensively used in aviation structural parts, is utilized as the experimental model. The effect of the keyhole mode on the migration behavior of SiC particles in the weld pool was revealed by simulating the multiphysical thermal fluid flow during the laser-welding process. The simulation results revealed that the flow of the molten pool and the keyhole mode have significant effects on the migration behavior of particles. The variation of keyhole mode leads to considerable changes in molten pool dynamics and corresponding SiC particle distributions in the molten pool. The observed selective distribution of SiC particles is due to the flow characteristics of the molten pool. In addition, results showed that the keyhole mode can maximize the uniform distribution of SiC particles in the melt pool, thereby addressing the nonuniformity problem of SiC particles. This work is a fundamental advancement in the modeling of laser-welded SiC particle–reinforced Al matrix composites and provides unprecedented details on the effects of keyhole patterns on weld pool dynamics. This work can further offer practical guidance for “temperature field–regulating reaction behavior” and “velocity field–regulating distribution behavior.”

Study of deep transportation and plugging performance of deformable gel particles in porous media

Deformable gel particles (DGPs) possess the capability of deep profile control and flooding. However, the deep migration behavior and plugging mechanism along their path remain unclear. Breakage, an inevitable phenomenon during particle migration, significantly impacts the deep plugging effect. Due to the complexity of the process, few studies have been conducted on this subject. In this paper, we conducted DGP flow experiments using a physical model of a multi-point sandpack under various injection rates and particle sizes. Particle size and concentration tests were performed at each measurement point to investigate the transportation behavior of particles in the deep part of the reservoir. The residual resistance coefficient and concentration changes along the porous media were combined to analyze the plugging performance of DGPs. Furthermore, the particle breakage along their path was revealed by analyzing the changes in particle size along the way. A mathematical model of breakage and concentration changes along the path was established. The results showed that the passage after breakage is a significant migration behavior of particles in porous media. The particles were reduced to less than half of their initial size at the front of the porous media. Breakage is an essential reason for the continuous decreases in particle concentration, size, and residual resistance coefficient. However, the particles can remain in porous media after breakage and play a significant role in deep plugging. Higher injection rates or larger particle sizes resulted in faster breakage along the injection direction, higher degrees of breakage, and faster decreases in residual resistance coefficient along the path. These conditions also led to a weaker deep plugging ability. Smaller particles were more evenly retained along the path, but more particles flowed out of the porous media, resulting in a poor deep plugging effect. The particle size is a function of particle size before injection, transport distance, and different injection parameters (injection rate or the diameter ratio of DGP to throat). Likewise, the particle concentration is a function of initial concentration, transport distance, and different injection parameters. These models can be utilized to optimize particle injection parameters, thereby achieving the goal of fine-tuning oil displacement.

Particle migration behavior of fractured lost circulation control: Numerical simulation

Fracture loss is the most common type of leakage in petroleum drilling engineering. The existing numerical simulation of the particle transport process is relatively simplified. In order to clarify the dynamic behavior characteristics of bridging particles in fractures, this paper adopts the discrete element and computational fluid dynamics coupling numerical simulation methods to establish a bidirectional coupling numerical model of bridging particles and drilling fluid to simulate the dynamic evolution process of bridging plugging particles, such as migration, bridging, and accumulation. The results show that the main factors affecting the transport pattern of plugging particles in the fracture are differential pressure, particle size, drilling fluid viscosity, drilling fluid density, fracture width, and fracture length. The drilling fluid density has a small effect on the inter-particle force in the fracture; the drilling fluid viscosity mainly affects the resistance of the particles, and the pressure difference between the inlet and outlet of the fracture mainly affects the transport speed of the particles. The particle size determines whether a plugging layer can be formed, and the best plugging effect is achieved when the particle size is 1/2 of the fracture width.

Particle migration behavior between TiO2 and magnetite under high-temperature oxidative roasting: An experimental and molecular dynamics study

Particle migration behavior between TiO2 and magnetite under high-temperature oxidative roasting: An experimental and molecular dynamics study

Molten Pool Dynamics and Particle Migration Behavior during TIG-assisted Droplet Deposition Manufacturing of SiC Particle-reinforced Aluminum Matrix Composites

Molten Pool Dynamics and Particle Migration Behavior during TIG-assisted Droplet Deposition Manufacturing of SiC Particle-reinforced Aluminum Matrix Composites

Fluid flow-induced fine particle migration and its effects on gas and water production behavior from gas hydrate reservoir

Natural gas hydrates are widely distributed in silty marine sediments containing fine particles less than 75 μm in size. The effects of WC (water content) on the behavior of fine particle migration and their role in gas and water production do not appear well understood. This work found that the WC slightly affected the gas production pattern in uniform sandy reservoirs. Yet upon a mixture of coarse and fine particles, the fine particles would instantly aggregate at the nearby pore throat reducing the reservoir permeability and prolonging the production by more than 3 times. Surprisingly, 16% of the fine particles at the edge and 19% at the middle were found to migrate with the fluid flow upon increasing water content, resulting in a less hindered initial gas production but a following more complete blockage or even production failure. This behavior can be consolidated in the scenario of a sand-kaolin mixture. The findings could provide new knowledge on the particle migration behavior upon gas and especially water production and guide the strategy design on dealing with the sand problem in the field test.

Analysis of the effect of shoulder cleaning on particle migration within ballast based on a coupled CFD-DEM approach

The ballasted track is vulnerable to fouling caused by penetration of foreign materials or degradation of aggregates. Proper maintenance can open the clogged drainage path within the ballast and ease other track issues for both short-time and long-term use. Shoulder cleaning is one of the popular ballast manntenance methods that present promising results in the field practices. Therefore, insights of flow physics coupled with particle dynamics within the fouled ballast will benefit maintenance decision makings. This paper presents a simulation-based analysis on the effect of shoulder cleaning on fine particle migration and its influence on ballast drainage. Various factors governing particle-laden gravity-driven flow within the ballast with and without shoulder cleaning are considered, including the fouling index, fouling profile, and cohesive energy density (interparticle bonding forces that depend on the contact area between two particles). The simulations for fine particle migration are carried out under multiple different fouling scenarios using the computational fluid dynamics and discrete element method (CFD-DEM) to capture the interactions between fine particles/particles and fine particles/flow. A parameter named ‘local fouling index’ is introduced for the first time to track the particle migration at different regions within the ballast, characterize the local fouling conditions, and evaluate the non-uniformity in fouling severity. The results indicate that the particle migration behavior is considerably influenced by those factors above, and shoulder cleaning is more effective for particle removal and drainage restoration when the fine particles trapped in the ballast have higher cohesive energy densities.

Study on the effect of ionic strength on particle migration and deposition in porous media covered by biofilm based on coupled Lattice Boltzmann method and Discrete element method

AbstractBiofilms covering porous media will interact with particles and affect particle migration. In order to investigate the migration mechanism of particles in porous media covered by biofilms, the migration process of particles with different particle sizes under the condition of the changing ionic strength is analyzed by using the lattice Boltzmann method–discrete element method (LBM‐DEM) coupling method from mesoscopic scale. The variation patterns of ion strength include gradient and mutation, respectively. Also, the agglomeration of particles at the pore throat in porous media is investigated under different conditions. The main results are obtained as follows. First, both the change of ionic strength and its changing mode significantly affect the migration behavior of particles in NaCl solution but have little effect on the behavior of particles in CaCl2 solution. Second, when the pressure difference between the pressure difference between the inlet and outlet of porous media is 0.4 kPa, the residual permeability of 1.5‐μm particles in the NaCl solution with ionic strength mutation is the highest, which has value of 64.92%. Third, at the specific flow rate, the particles in low ionic strength solution are more likely to be settled. The attraction of particles in the CaCl2 solution is one order of magnitude less than that in the NaCl solution, and the accumulated particles are more likely to be dispersed.

The application of machine learning models based on particles characteristics during coal slime flotation

In this study, four different machine learning (ML) models were used to simulate the migration behavior of minerals during coal slime flotation based on particle characteristics (shape, size, compositions, and types): random forest (RF), logistic regression (LR), AdaBoosting (Ada), and k-nearest neighbors (KNN). For ML model development, 70% of the total data was used for the training phase, and 30% was used for the testing phase. F-score and area under the curve (AUC) were used as the most vital indicators for evaluating the different ML models. Compared to the other ML models, the RF model had the best accuracy for simulating particle migration behavior during flotation. Furthermore, the RF model avoided the drawback of having to be retrained when the feed conditions changed. The results revealed that particle size and particle composition play the most significant role in coal slime flotation.

Simulation of particle migration during viscosity measurement of solid-bearing slag using a spindle rotational type viscometer

A Discrete Phase Model (DPM) is adopted to investigate the particle behavior during viscosity measurement of solid-bearing slags. The particle-particle interaction is interpreted by the Discrete Element Method (DEM). The results show that the particle migration is a function of shear time, leading to continuous changes in variable viscosity before a critical shear time. The critical shear time and therefore the viscosity measurement depend on the operational conditions through the particle migration behavior that is influenced by the shear time, rotational speed, gap width and particle content, shape and size. The study of particle size indicates a size segregation of the initially homogeneous system. Based on our results a number of guidelines are formulated to assist in developing more reproducible viscosity measurement methodologies.

Crossly charged microfluidic device for spontaneous filtration without an external power supply

Spontaneous filtration without a power supply was investigated using highly charged precursor mixtures instead of recognized microfluidic desalination techniques. The proposed filtration method consisted of a main channel (depth: 1 mm) and shallow channels (depth: 400 μm) in which the precursor mixture was injected. The filtration performance of the proposed device was evaluated by injecting a fluorescent dye that moved toward the centerline of the main channel. The respective rejection rates of CaCl2, NaCl, CaSO4, and Na2SO4 were 3.16%, 30.13%, 43.74%, and 36.32%, respectively. This trend can be explained by the mechanism of Donnan exclusion theory. The focusing of charged species toward the centerline of the main channel was caused by highly charged surfaces. The proposed filtration method exhibited a migration of charged microparticles toward a certain direction. This particle migration behavior was consistent with the simulation data. These results suggested that the proposed filtration method had strong potential for desalinating brackish water or salty surface water without an external power supply.

Predictions of fiber concentration in injection molding simulation of fiber-reinforced composites

The microstructures of injection-molded short fiber composites, involving fiber orientation and fiber concentration, strikingly influence flow behaviors and mechanical properties. Through the use of certain commercial software, reported numerical predictions of fiber orientation for the shell–core structure have been obtained to date. However, no work has been done on fiber concentration prediction available in processing simulations. In the theoretical field of suspension rheology, the suspension balance (SB) model has proven successful in capturing particle migration behavior under the simple Couette shear flow of “spherical” particle suspension, hence the attempt to verify the SB model applied in the “like-rod” suspensions. To predict flow-induced variations of fiber concentration, the SB model is implemented in 3-D-injection molding simulation with more general flows. It is remarkable for the shell–core structure is explored to reflect the relationship between fiber orientation and fiber concentration.

Quantitative characterization of the focusing process and dynamic behavior of differently sized microparticles in a spiral microchannel

In this paper, a spiral microchannel was fabricated to systematically investigate particle dynamics. The focusing process or migration behavior of different-sized particles in the outlet region was presented. Specifically, for focused microparticles, quantitative characterization and analysis of how particles migrate towards the equilibrium positions with the increase in flow rate (De = 0.31–3.36) were performed. For unfocused microparticles, the particle migration behavior and the particle-free region’s formation process were characterized over a wide range of flow rates (De = 0.31–4.58), and the emergence of double particle-free regions was observed at De ≥ 3.36. These results provide insights into the design and operation of high-throughput particle/cell filtration and separation. Furthermore, using the location markers pre-fabricated along with the microchannel structures, the focusing or migration dynamics of different-sized particles along the spiral microchannel was systematically explored. The particle migration length effects on focusing degree and particle-free region width were analyzed. These analyses may be valuable for the optimization of microchannel structures. In addition, this device was successfully used to efficiently filter rare particles from a large-volume sample and separate particles of two different sizes according to their focusing states.

Particle migration in oscillatory torsional flows of concentrated suspensions

This study presents an experimental investigation into particle migration behavior of concentrated suspensions of noncolloidal spheres in oscillatory torsional flows between parallel plates. Video imaging of the radial drift velocity of dyed tracer particles in a monodisperse, 0.4 bulk particle volume fraction suspension was performed during flow evolution. In conjunction with simultaneous rheological measurements, particle tracking provided insight into migration phenomena. For all of the cases studied, the average displacement of the tracer particles per cycle was directed radially outward and was approximately a linear function of the oscillatory strain amplitude while also varying with the frequency of oscillation in a nearly inverse square relationship. The measured radial migration velocity exceeded that estimated from the suspension balance continuum model for a corresponding steady flow, likely due to the increased microstructural mobility developed during oscillatory flow. Generally, the oscillatory torque increased as the flow evolved, while local minima in the torque ratio and radial drift velocity were detected at intermediate strain values, in agreement with recent studies of oscillatory flow. The results suggest the competition between radial shear-induced particle migration driven by the overall particle stress balance and rearrangement of particles into an ordered microstructure driven by local interactions.

Swimming Hydrodynamics of a Run-And-Tumble Bacterium with Helical Flagella

To study the swimming of a peritrichous bacterium such as Escherichia coli, which is able to change its swimming direction actively, we simulate the “run-and-tumble” motion using a bead-spring model to account for the hydrodynamic and the mechanical interactions between the cell body and multiple flagella, the reversal of the rotation of a flagellum in a tumble and the associated polymorphic transformations of the flagellum. The cell body and each flagellum are connected by a flexible hook, so that the flagella can take independent orientations with respect to the cell body. This simulation reproduces the experimentally observed behaviors of E. coli, namely, a three-dimensional random-walk trajectory in run-and-tumble motion and steady clockwise swimming near a wall. We show that the polymorphic transformation of a flagellum in a tumble facilitates the reorientation of the cell, and that the time-averaged flow field near a cell in a run has double-layered helical streamlines, with a time-dependent flow magnitude large enough to affect the transport of surrounding chemoattractants. This new model, which can be refined by using more beads if more quantitative predictions are desired, strikes a balance between accuracy and simplicity that will permit it to be used to determine the migration behavior of particles near a swimming cell, cell-cell hydrodynamic interactions, the effect of the number and geometric distribution of flagella on migration, the mechanism of circular swimming near a wall, details of the tumbling motion, and the effect of the Brownian motion on swimming. We also develop minimal models, inspired by the simple model of Najafi and Golestanian, that contain only 3-5 beads, and can simulate simple “pusher” and “puller” micro-swimmers, and are also able to include helical flow typically produced by rotary flagellar motion.