Motion Trajectories Of Particles Research Articles

Resonance and surfactant effects on the interaction of a rising bubble and a sedimenting particle in an oscillating fluid

This paper considers the interaction of a rising bubble and a sedimenting fine particle in a liquid with a soluble surfactant subjected to the gravity field, forced flow, and vibrations. The frequency of vibrations is close to the resonance value. The particle motion trajectories are calculated, taking into account its inertia, fluid viscosity, Basset force, buoyancy force, and the mean force acting on the particle due to the inhomogeneity of the pulsating field. The collision efficiency is evaluated, and the cross sections of the sedimenting particles captured by the rising bubble are found. It is demonstrated that even at low vibration intensity but in the presence of a weak surfactant effect, a significant increase in the probability of particle–bubble collision and in the capture cross section can be achieved. The obtained results can be used to intensify the flotation processes by ultrasonic treatment.

Study on the tribocharging properties of MgCO3 particles based on LFN-en-A model

Abstract As an efficient and environment-friendly method, electrostatic separation has gradually replaced flotation methods in the separation of magnesite in recent years. In the process of triboelectrostatic separation, the mineral particles are tribocharged driven by the air flow, then the trajectory is shifted under the action of the electric field, so as to realize the separation. The useful mineral in magnesite is MgCO3, but the theoretical research related to the charge characteristics of MgCO3 is not sufficient. Particle image velocimetry (PIV), as an indirect measurement technique, is able to obtain the velocity field of the fluids from images. However, the particles moving in the air have the issues such as excessive speed and small particle size, which make the traditional PIV has low accuracy in estimating the motion of particles. In this paper, a high-speed camera is used to capture the motion trajectory of tribocharged MgCO3 particles in a parallel electric field. A new optical flow method LFN-en-A network based on LiteFlowNet-en network is proposed to compute the particle motion trajectory by combining the deep learning method with the traditional PIV, which realizes the displacement estimation of particles moving in the air. It ultimately realizes the calculation of the charge-to-mass ratio on single particles. Analyzing the accuracy of the LFN-en-A network’s estimation in the experiments, the estimation of LiteFlowNet-en was compared. Changing the shooting frame rate analyzes the optimal one required by the LFN-en-A network. Combining the estimation results of LFN-en-A to calculate the particle charge-to-mass ratio (Q/m), the Q/m of MgCO3 particle was analyzed by changing the experimental conditions in the process of particles’ tribocharging, which provided a new method for particle-to-charge ratio measurement.

Development of Models Relating Screw Conveying Capacity of Concrete to Operating Parameters and Their Use in Conveyor Operating Strategies to Consider Batch Production

The screw conveyor is the key equipment used to realize the casting and forming of concrete in prefabricated components (PC), and its performance affects the PC shape, quality, and cost. In batch production, there is a process variable, the residence time. It is affected by the quality of the downstream vibration process. This also results in operating parameters that are difficult to match to the time scales. Eventually, it can lead to problems such as low casting efficiency or poor molded quality. In this paper, the DEM simulation method is used to explain and quantify the relationship between the screw conveying capacity and three important operating parameters: the screw’s outer diameter, residence time, and screw speed. The axial and radial velocity vectors are used as features to analyze the changing rule of particle motion trajectory and mass flow rate. Based on the simulation data, the operating parameters and the mass flow rate are forward-fitted to establish the prediction model of the screw conveying capacity. In addition, the residence time is backward fitted from the screw speed and mass flow rate. It is used to estimate the concrete workability. Furthermore, the fitted forward and backward models explore how to propose feasible operational strategies to achieve automatic discharge during batch production.

Generation of chiral optical vortex lattice for controlled aggregation of particles

The chiral light field has attracted great attention owing to its interaction with chiral matter. The generation of chiral light fields with rich structures has become crucial as it can expand application scenarios. Herein, we introduce a chiral optical vortex lattice. As a whole, the optical vortex lattice has a chiral intensity distribution, with each spiral arm having sub-vortices (chiral phase). By using an expansion factor to adjust the involute of a circular lattice, this helical optical vortex lattice can be continuously varied from a circular lattice. The chirality of intensity and phase can be controlled independently. Furthermore, the optical tweezers using the lattice demonstrate the capability of sub-vortices to manipulate particle movement, with the chiral intensity determining the trajectory of particle motion. As the lattice possesses both intensity and phase chirality, it may also find potential applications in tasks such as chiral structure microfabrication.

Study on the motion characteristics of bedload sediment particles under different sediment transport intensities

AbstractBedload studies at the particle scale may help grasp the essence of the problem. Existing studies suffer from short filming durations, limited data volume, and a narrow range of sediment transport intensity variations. This paper employs the high‐speed photography technology and conducts experimental studies on bedload particle motion under 8 different sediment transport intensities. Using the latest image processing technology, over 6 million sediment particle coordinate points and nearly 400,000 particle motion trajectory curves were automatically obtained and used to compare the motion characteristics of bedload particles under different sediment transport intensities. The results show that under low sediment transport intensity, both the number of moving particles and particle motion velocity contribute to the bedload sediment transport rate, while under high‐intensity conditions, the transport rate mainly depends on the number of moving particles. The probability density distribution of sediment transport rate is concentrated and varies within a small range under low‐intensity conditions, exhibiting a tailing phenomenon. In contrast, under high‐intensity conditions, the range of sediment transport rate values increases, and the probability density curve tends to be symmetric, more closely approximating a normal distribution. Additionally, the paper compares the longitudinal and transverse motion velocities of particles and the coefficient of variation of the bedload sediment transport rate.

Numerical Investigation of Micrometer-Sensitive Particle Intrusion in Hydraulic Valve Clearances and Its Impact on Valve Performance

The intrusion of micrometer-sensitive contaminant particles into the clearance of sliding valves within hydraulic fluids is one of the root causes of valve sticking and reliability issues in hydraulic systems. To reveal the transient process and characteristics of particle intrusion into the clearance process, this paper proposes a numerical method for fluid–particle one-way coupling and verifies it through experimentation. Furthermore, a numerical simulation of the motion trajectory of spherical iron particles inside the valve chamber was conducted in a two-dimensional flow model. It was discovered that in a steady-state flow field with a certain valve opening, micrometer-sized particles in the valve chamber’s hydraulic fluid mainly move with the valve flow stream, and the number of micron particles invading the slide valve clearance and the probability of invasion is related to the slide valve opening and differential pressure. When the slide valve opening decreases, especially in the small opening state, the probability of particles invading the slide valve clearance will increase dramatically, and the probability of invading the clearance is as high as 27% in a valve opening of 50 μm; the larger the pressure difference between the valve ports, the more the number of particles invading the slide valve clearance increases; the particles in the inlet of the slide valve clearance are more prone to invade the slide valve clearance, and invade in an inclined way, touching the wall and then bouncing back. These findings are of great value for the design of highly reliable hydraulic control valves and the understanding of the mechanism of slide valve stalls and provide an important scientific basis for the optimization and improvement in the reliability of hydraulic systems.

Fluid–Solid Mixing Transfer Mechanism and Flow Patterns of the Double-Layered Impeller Stirring Tank by the CFD-DEM Method

The optimization design of the double-layered material tank is essential to improve the material mixing efficiency and quality in chemical engineering and lithium battery production. The draft tube structure and double-layered impellers affect the flow patterns of the fluid–solid transfer process, and its flow pattern recognition faces significant challenges. This paper presents a fluid–solid mixing transfer modeling method using the CFD-DEM coupling solution method to analyze flow pattern evolution regularities. A porous-based interphase coupling technology solved the interphase force and could be used to acquire accurate particle motion trajectories. The effect mechanism of fluid–solid transfer courses in the double-layered mixing tank with a draft tube can be obtained by analyzing key features, including velocity distribution, circulation flows, power, and particle characteristics. The research results illustrate that the draft tube structure creates two major circulations in the mixing transfer process and changes particle and vortex flow patterns. The circulating motion of the double-layered impellers strengthens the overall fluid circulation, enhances the overall mixing efficiency of the fluid medium, and reduces particle deposition. Numerical results can offer technical guidance for the chemical extraction course and lithium battery slurry mixing.

Experimental and numerical investigation of abrasive water jet nozzle erosion

In this paper, the particle flow inside the nozzle is simulated by Computational Fluid Dynamics (CFD) method and the numerical results are verified by experimental observation. The motion trajectories of incident particles in different regions are investigated through trajectory analysis. In addition, the erosion damage mechanism was analyzed by the surface morphology and impact characteristics of the main abrasion region. The results show that the particle impact position gradually moves forward as the particle incident position moves away from the inlet center. Sensitivity analyses showed that erosion rate was most sensitive to pump pressure; impact frequency, impact velocity and impact angle were most sensitive to particle size, pump pressure and particle size, respectively. Due to the low angle impact of particles, the corresponding erosion damage mechanism is micro-cutting.

Motion and dispersion characteristics of graphite particles in a bottom-blown converter for molten slag reduction

In order to improve the recovery of iron resource in molten basic oxygen furnace (BOF) slag through carbothermal reduction, bottom blowing argon gas is used to promote the mixing efficiency between molten slag and graphite particles in the converter. In the present work, computational fluid dynamic-discrete particle model (CFD-DPM) method coupled with the reduction kinetic model of FeO in molten slag by graphite particle is employed to simulate the multiphase system composed of molten slag, graphite particle and argon gas. The motion and dispersion characteristics of graphite particles in a bottom-blown converter were mainly investigated, and the decrease of graphite particle diameter caused by the reduction reaction was considered. A particle dispersion index was also proposed to evaluate the distribution uniformity of graphite particles in the molten slag. In addition, the effects of initial particle diameter and bottom tuyere arrangement on the dispersion characteristics of graphite particles were further discussed. The results show that the proportion of large-sized particles is higher in the inactive-flow zone and the motion trajectory of graphite particles can be divided into two regimes. Graphite particles with an initial diameter of 5 mm and the converter with six bottom-blown tuyeres are more conducive to the homo-dispersion of graphite particles.

Study on Gas-solid Two-phase Flow Field of Ramon Mill Classifier

To reveal the working principle and internal flow field law of the grading machine, the numerical simulation of the gas-solid two-phase flow field was carried out. In this paper, the numerical simulation method based on Fluent is used to obtain the internal velocity distribution and pressure distribution of the grading machine. The flow field of gas-solid two-phase was studied based on the CFD-DEM coupling, and the particle motion trajectory in the grading machine and the particle motion law in the flow field at different times were obtained; The influence of the operating parameters of the internal flow field on the force of particles in the grading machine was analyzed, and combined with the change of particle number, the particle collection efficiency of the grading machine under different operating parameters was further given. It is of guiding significance to adjust the parameters of the grading machine, improve the output and the product quality of the longitudinal mill, and reduce the energy consumption of the longitudinal mill.

Feasibility Analysis of Calcium Carbonate Particle Trajectory Simulation in a Dual Horizontal Shaft Mixer.

This article aims to investigate the feasibility of using discrete element software EDEM 2022.0 to simulate the trajectory of artificial marble patterns in a dual horizontal shaft mixer. Research was conducted on the mixing uniformity of particles in the mixing chamber, and the optimal speed range for particle mixing was established. By simulating the trajectory of pigment particles, the trajectories of the particles at different positions of the stirring paddle were obtained, and the trajectories were compared with the measured results. In the study of uniform particle mixing, the Lacey index at different speeds was compared, and the optimal speed range was established between 40 RPM and 60 RPM. Based on this, the particle trajectory simulation found that the motion trajectories of particles at different positions of the stirring paddle varied significantly. The particles in the stirring paddle rod exhibit a gradual trend, in which they gradually decrease as they approach the head of the stirring paddle. Finally, the feasibility of this method was established by comparing the simulated and actual patterns through proportional replication of the mixing process, and it was discovered that the two were similar.

Dust deposition mechanism and output characteristics of solar bifacial PV panels.

The utilization of solar photovoltaic (PV) power generation represents a highly promising technological solution for addressing environmental challenges and energy crises. Dust deposition on the front and back surfaces of solar bifacial PV panels greatly decreases the optical performance and power generation. In this study, the dust deposition characteristics and mechanism of solar bifacial PV panels are investigated using the CFD-DEM method. The effects of the dust deposition rate on the output characteristics of bifacial PV panels are discussed. The research results show that the particle deposition behaviors on the back and front surfaces of bifacial PV panels are influenced by the deposition and separation forces at the left or right inlets. The dust deposition rate of windward surfaces can be 1.48-7.60 times that of the leeward surfaces of bifacial PV panels. The particle motion trajectories on the windward and leeward sides can be mainly divided into five and three kinds, respectively. The dust deposition rate of bifacial PV panels increases when the air inlet velocity decreases and the particle size and concentration and relative humidity increase. The open circuit voltage and short circuit current of bifacial PV panels decreased by 26.7% and 16.4%, respectively, when the dust deposition rate increases by 45.8%. The attenuation rate of the maximum output power of PV panels has a positive linear correlation with the dust deposition rate, as shown in Eq. 22. The bifacial PV panels have better output characteristics than the mono-facial PV panels with consideration of dust deposition.

Effect of proppant sizes and injection modes on proppant transportation and distribution in the tortuous fracture model

Particle-fluid transport and placement mechanism in tortuous fracture played a crucial role in unconventional reservoirs. Currently, most studies focused on mono-size proppant with fluid transport processes in tortuous fractures. However, the mixture-size proppant with fluid movement mechanism in tortuous fracture was still uncommon. Therefore, this study designed and applied a series of experiments with a physical analog model of a tortuous fracture with 120° and 90°-angled bends and combined high-speed camera-based equipment. This experimental system was used to track different-mixture-sized proppant particle motion trajectories for a series of proppant injection schemes; The following conclusions were drawn from this study:1. The pile-up processes mechanism in all investigated schemes were similar and could be reduced to four main stages. 2. The packing structure at both sides of the fracture wall had different variation rates, which were controlled by the mix ratio (change from 1:1–1:5) of proppant size. 3. Some new packing patterns, such as Zebra Stripe, had occurred, controlled by the different proppant injection sequences. 4. Small-sized mono-proppant (30/50 mesh) had the highest transport efficiency in the tortuous fracture, followed by the mixed-sized multi-proppant (10/20 mesh:30/50 mesh), large-sized proppant (10/20 mesh) was the worst. 5. An optimized alternating injection mode was recommended as injecting small-sized proppant first (30/50 mesh) and followed by mixed-sized multi-proppant (10/20 mesh:30/50 mesh), which could contribute to obtaining the optimal both proppant packing height and travel distance in tortuous fracture.6. Two correlations were developed for predicting the proppant packing height and transportation distance.

Hyperchaos, constraints and its stability control in a 6D hyperchaotic particle motion system

Firstly, a novel six-dimensional (6D) hyperchaotic particle motion system is formulated. The equilibrium points and their characteristics, Poincaré sections, Lyapunov exponents, bifurcations and multi-periodic windows are studied. Secondly, we present two nonholonomic constrained systems. In order to analyze the particle motion trajectories under constraints, the explicit equations for constrained systems are given. Based on Lyapunov exponents, Poincaré maps and bifurcations, we can see that the different hyperchaotic phenomena of the particle motion can be generated by introducing nonholonomic constraints. Finally, the stability control of the 6D hyperchaotic particle motion system is realized by separately using constraint control method and linear feedback control method. Numerical simulations of the dynamical behaviors of the six-dimensional hyperchaotic particle motion system are carried out in order to illustrate the complex phenomena of the systems and verify the analysis results.

Reinforcing effect of cross baffles on mass transfer process in raceway photobioreactors

AbstractAdding baffles inside raceway photobioreactors is a method to strengthen mixing. In this paper, a new type of staggered baffles are designed and compared with other structural baffles. Computational fluid dynamics was used to analyze the mixing effect of baffles with different structures in the raceway photobioreactors. The light–dark cycle of the staggered baffles was analyzed by coupling the motion trajectories of dynamical proton model particles through the change of outdoor light intensity during the day. The light–dark cycle of the cross baffle was analyzed according to the change of outdoor light intensity during the daytime coupled with the motion curve of dynamical proton model particles. The mixing ability of the staggered baffles was verified by mixing time, mass transfer coefficient, and outdoor cultivation. The results show that when the speed of the paddlewheel reached 20 rpm, compared with the raceway photobioreactors without baffles, vorticity increased by 23.3% respectively; the light–dark cycle period reduced by 18%; the mixing time reduced by 40%, and the mass transfer coefficient increased by 9.67%, the biomass of Chlorella increased by 25.3%. Compared with the other two baffle structures, the light–dark cycle period was reduced by 7.3% and 5.9%, the mixing time was reduced by 15% and 8%, and the mass transfer coefficient was increased by 1.17% and 3.59%. The biomass increased by 8.3% and 4.8%. The staggered baffles have better mass transfer performance, which can provide a reference for the optimal design of raceway photobioreactors.

A theoretical model for calculating particle trajectory in a vane-type separator

A vane-type separator has been successfully applied to gas-liquid and liquid-liquid separation. In order to evaluate the separation performance of the separator, a theoretical model for calculating the particle motion trajectory in the vane-type separator was developed. Firstly, the simplified steady incompressible Navier-Stokes equations were derived to acquire the equations of tangential velocity and axial velocity of continuous phase flow field. Then, the coefficients were determined by fitting the CFD results and it can be used to obtain the velocity at different swirler structure conditions. Further, the force analysis on the particle was conducted to develop the motion governing equations to predict the trajectory. The predicted separation lengths at different geometric swirl number conditions show a good agreement with the experimental results and its relative error is smaller than 3%. Besides, the effects of the key parameters including density difference, particle size and viscosity of the continuous phase on the separation length were investigated.

Coupling Characteristics of Powder and Laser of Coaxial Cone Nozzle for Laser Direct Metal Deposition: Numerical Simulation and Experimental Study.

Laser direct metal deposition (LDMD) enables not only the preparation of high-performance coatings on the surfaces of low-property materials but also the three-dimensional direct manufacturing and re-manufacturing of parts. In the LDMD process, the spatial coupling characteristics of the powder flow and the laser beam are the key factors affecting the forming quality of the cladding layer. Based on the gas-solid two-phase flow theory, a numerical model of coaxial powder feeding was established by CFD. The powder flow characteristics of the lower part of the nozzle, the powder particle motion trajectory, and the optical-powder spatial coupling morphology and law were studied, and the relationship between the powder flow morphology, laser beam, and powder utilization was explored. On this basis, the law between the optical-powder coupling characteristics and the geometric characteristics of the cladding layer is discussed in conjunction with LDMD experiments. The results show that the powder concentration scalar located in the focal plane of the laser beam can be used to visualize the optical-powder coupling morphology. When the powder feeding speed exceeds the loading capacity of the carrier gas flow, the powder concentration in the center of the spot and the powder utilization rate decrease. When the carrier gas flow rate is 4.0 L/min and the powder feeding rate is 4.0 g/min, the best utilization rate achieved is 81.4%. In addition, the H (height) of the cladding layer is more sensitive to changes in the powder concentration than the W (width). These findings provide new ideas for nozzle structure design and the optimization of LDMD parameters.

STUDY OF THE MOVEMENT OF A MATERIAL PARTICLE ON A FLAT DISK ROTATING AROUND A PERPENDICULAR AXIS INCLINED TO THE HORIZON

The movement of material particles along rotational planes is complex, since it should be considered as the result of the movement of the plane itself and the particle along this plane. The task becomes more difficult if the moving plane is inclined at a certain angle to the horizon. Its solution makes it possible to find out the regularities of the movement of a particle along an inclined plane, which rotates around an axis perpendicular to it. The purpose of the study is to establish the patterns of movement of material particles on a flat disc with and without blades, which rotates around a perpendicular axis inclined to the horizon. If a round disk rotating around an axis perpendicular to it is located horizontally, then the kinematic parameters of the particle's motion on it do not depend on the point of impact of the particle on the disk. If the disk is tilted at a certain angle β to the horizon, it is obvious that the absolute trajectories of the particle's movement and other parameters of the movement will not be the same and will depend on the sector of the disk from which the particle starts its movement. The relative and absolute motion of a particle on an inclined disk with and without rectilinear blades is considered. A system of differential equations of particle motion has been compiled using the accompanying trihedron of the transfer trajectory, which is a circle, and Frenet's formulas. Numerical integration of the system was carried out. The obtained results were visualized. It was established that when particles hit an inclined disk that rotates around its own axis, the absolute trajectories of motion differ significantly from the trajectories of motion along a horizontal disk, and the difference in trajectories increases with an increase in the angle of inclination β. If rectilinear vanes are installed on the disc in the radial direction, the difference between the particle motion parameters will increase insignificantly as the angle β increases. When increasing the angular speed of rotation of the disk at a given angle, the shape of the absolute trajectories of particle motion practically does not change, but they are different depending on the point of impact on the disk. There is a certain area of impact and a certain sector of trajectories, after passing which the particle flies up after leaving the disc. Among this set, it is possible to analytically find the point of impact and the corresponding trajectory, which provide the maximum angle of elevation of the particle (equal to the angle β).

DEM Study of the Motion Characteristics of Rice Particles in the Indented Cylinder Separator.

The precise separation of rice particles is an important step in rice processing. In this paper, discrete element simulations of the motion of rice particles of different integrity in an indented cylinder separator were carried out using numerical simulation methods. The effects of single factors (cylinder rotation rate, cylinder axial inclination angle, and collection trough inclination angle) on the motion trajectories of particles are investigated and the probability distribution functions of particles are obtained. The statistical method of Kullback-Leibler divergence is used to quantitatively evaluate the differences in the probability distribution functions of the escape angles of particles of different degrees of integrity. The purpose of this paper is to determine the optimum parameters for an indent cylinder separator by understanding the material cylinder separating process from particle scale and to provide a basis for the numerical design of a grain particle cylinder separators.

Study on Migration Law of Solid Particles on Sieve Surface of Solid-liquid Separator

Based on the discrete element method and the three-dimensional discrete element analysis software EDEM, simplify the tube net type solid liquid separator model, to explore the net type solid liquid separator inside the cylindrical screen opaque screen the migration law of solid phase particles and different vibration frequency, vibration amplitude, vibration direction Angle, diameter of sieve sieve speed and sieve cylinder is opaque screen the influence of solid phase particles migration rule, In order to provide reference for the selection of structural parameters and vibration parameters of solid-liquid separator in field application. The results show that the motion trajectory of solid particles on the screen is a three-dimensional spiral curve. The larger the vibration frequency and amplitude of the screen box, the higher the particle migration speed. The larger the vibration direction Angle, diameter and speed of sieve box, the smaller the particle migration speed. The research results can be used for reference in the selection of structural parameters and motor vibration parameters that affect the comprehensive performance of the cylinder net solid-liquid separator.