Motion Characteristics Of Particles Research Articles

Experimental study on the unsteady evolution mechanism of centrifugal pump impeller wake under solid–liquid two-phase conditions: Impact of particle concentration

To study the spatiotemporal evolution process of particle wakes behind the impeller in the centrifugal pump, this paper utilized high-speed photography to capture the particle motion characteristics under different solid-phase particle concentrations (1%, 1.5%, and 2%). First, this paper studies the changes in hydraulic performance of the centrifugal pump under solid–liquid two-phase flow conditions. It then introduces the evolution process of the impeller particle wake, comparing the differences in particle wake evolution under varying solid-phase concentrations. Finally, the impact of the solid-phase concentration on the wear of the volute's partitions is investigated. This study found that as the solid-phase particle concentration increases, the hydraulic performance of the pump gradually declines. Under the design conditions, when the solid-phase concentration increases by 0.5%, the efficiency of the centrifugal pump decreases by 0.56% and 0.35%. There is mutual transport of particles between adjacent wakes, and the movement of particle wakes within the volute passage is not equidistant over time. As the solid-phase particle concentration increases, wake cutting occurs at the volute partitions, and there is a significant solid–liquid separation between the particle wakes. The spatial evolution of the particle wakes is significantly influenced by the solid-phase concentration. Wear at the volute partitions intensifies with increasing solid-phase concentration and is also affected by changes in the particle wakes. The research results provide a basis for further exploration of the solid–liquid two-phase flow dynamics within centrifugal pumps.

Characterizing nodule motion in abyssal environments induced by double-row jets: A machine learning approach

Double-row hydraulic collectors are extensively utilized for deep-sea polymetallic nodule harvesting. Understanding the movement behavior of particles within the flow field is crucial for evaluating the efficiency collection system and guiding the design of deep-sea hydraulic collectors. This study first investigates the settling characteristics of particles in various deep-sea environments to assess the effects of high-pressure and low-temperature conditions on particle motion. Subsequently, the motion and force characteristics of particles under different double-row jet parameters were measured and analyzed in the laboratory using high-speed imaging. The results indicate that ambient pressure has a negligible effect on particle motion when the ambient temperature is considered. Particle is mainly lifted in an irregular spiral path by the turbulence of the upper fountain. The lifting height or force of a particle in the vertical direction is positively correlated with the frequency of horizontal fluctuations and inversely related to the average amplitude of these fluctuations. Finally, a neural network was constructed to predict the particle motion characteristics, demonstrating strong generalization and providing a reference for further use of artificial intelligence in extracting physical information of particles from the jet field. This study offers potential benefits for optimizing the design of the double-row jet collectors.

Numerical Study of Flow Field and Particle Motion Characteristics on Raw Coal Vertical Roller Mill Circuits

In order to improve the motion characteristics of particles in vertical roller mills (VRMs), the assumption that different structures of helical guide blades affect the internal flow field of the VRMs was put forward. The distributions of fluid velocity and vorticity in VRMs were analyzed, and the mechanism affecting the motion of particles and the separation performance was studied. The study took the MMLM2550 (supplied by Jiangsu Dahuan Group, China; grinding table diameter of 2550 mm) VRM as the research object, whose structure was improved by adding helical guide blades. The results showed that, with the increase in the width of blade, the air flow trajectory and the distribution of vorticity improved, which was conducive to the transport of particles. However, changing the thickness of the blade had little effect on the internal physical field of the VRM and particle motion characteristics. Therefore, the influence of blade’s thickness on these factors was ignored. With the increase in the number of helical guide blade turns, the direction of the helical guide blade remained consistent with the trajectory of the movement of particles, making it more conducive to the discharge of particles from the VRM. The height of the helical guide blade had a great influence on the flow field and the particle motion characteristics. The smaller the blade height, the greater the reflux in the primary separation zone, and stronger the irregular circulatory motion of particles, thus increasing the movement time and the distance of particles. With the increase in the number of blades, the airflow speed increased in the flow channel, so that the particles moved with the airflow at high speed, while the movement time was effectively shortened. The study provides valuable guidance for the improvement of VRM structures, and serves as a reference for characterizing the motion of particles and enhancing the internal flow field in VRMs.

Particle motion under turbulent eddies: Inspiration for fine minerals flotation

Turbulent flow ubiquitous in flotation machines and contain multi-scale eddies. Compared to static environments, turbulence can increase particle kinetic energy and promote particle-bubble collision in mineral flotation. However, there have been few quantitative studies on turbulent eddies that affect particle motion, which limits the precise flow control of flotation processes. In this study, the motion characteristics of particles in isotropic turbulence were measured by particle tracking velocimetry, and the relationship between turbulent eddy and particle motion was quantitatively analyzed by 7-scale wavelet transform and fast Fourier transform. The measurement results show that the particle moves upward following a rotating turbulent eddy, and turbulent eddies with sizes of 35–119 µm and 127–288 µm drives the motion of dp = 74 µm and dp = 200 µm particles respectively. The turbulent acceleration of particles within a turbulent eddy can be calculated as aλ=Cε2/3λ-1/3. This study provides an eddy control basis for mineral flotation performance improvement.

Particle motion characteristics on the rotational flow pneumatic conveying of horizontal-vertical pipeline

In this study, a rotational flow device (rotational blade) is developed and installed in the upstream of the particle inlet with the aim of improving the efficiency and capacity of pneumatic conveying. Firstly, this study analyzed the energy-saving effect of rotational flow based on the pressure drop and power consumption. The results shown that the optimal velocity can be reduced by a maximum of 18.7 % and the power consumption coefficient can be reduced by a maximum of 9.8 %. Furthermore, the distributions of particle concentration, velocity and pulsation velocity are analyzed by using electrical capacitance tomography (ECT) and particle image velocimetry (PIV) system. It is found that the particle velocity and velocity pulsation intensity for rotational flow are higher, and they have the ability to enhance particle suspension. Then, the power spectrum of the particle pulsation velocity shown that the rotational flow exhibited higher peak value at lower frequencies, indicating the particles are not easily deposited at pipe bottom. Finally, the auto-correlation of particle pulsation velocity indicated that the particle motion is more stable and has a longer period at low particle concentrations. The skewness factor and probability density function of particle pulsation velocity indicated that the use of rotational blades makes the particle pulsation velocity to deviate from the Gaussian distribution.

Research on the Collection Characteristics of a Hydraulic Collector for Seafloor Massive Sulfides

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

Examination of particle motion in fluidized bed flotation columns: Effect of particle shape

The critical analysis of particle dynamics within the flow field is vital for the optimization and enhancement of new fluidized bed flotation columns. Prior research has centered on the kinetic properties of auxiliary fluidized particles (glass spheres) in these columns [1]. However, in real-world applications, these particles undergo wear and transform into irregular shapes. This investigation seeks to explore the motion characteristics of particles of various geometries in a three- phase gas-liquid-solid environment. By quantifying the velocities of particles with different shapes, we aim to improve the evaluation of their dispersion and collision behavior with the column walls. First, the particle concentration distribution within the fluidized zone is continuously monitored through pressure sensors at various axial positions, allowing us to examine the concentration patterns of particles from different shape categories under various operational conditions. Second, the motion dynamics of particles within the fluidization zone are studied using high-speed camera techniques. Particle velocities are determined by correlating tracer particle velocities with black markers for precise measurement. To evaluate the frequency of particle-wall collisions, a modified collision model is applied to ascertain collision rates and to investigate the influence of shape parameters on such interactions. Lastly, the normal and tangential restitution coefficients are measured based on the trajectories of particles before and after collisions with the walls.

Particle motion characteristics of vertical pipe on a the horizontal-vertical pneumatic conveying system installed dune models in the different curvature elbows

To minimize energy consumption in transportation, a dune model is developed and installed in elbow with varying radii of curvature in the horizontal-vertical pneumatic conveying system in this study. The experimental study focuses on the effect of dune model in elbow with different radius of curvature on the pneumatic conveying system in terms of pressure drop, additional pressure drop coefficient, and the power loss coefficient. Furthermore, the particle concentration and velocity distribution are measures by using the electrical capacitance tomography (ECT) and the high-speed particle image velocimetry (PIV) technology. Finally, the particle pulsation velocity is analyzed to reveal the particle motion mechanism of vertical pipe with dune model by using the fourier transform and wavelet transform. The results indicate that the minimum gas conveying velocity is reduced by installing the dune model, with a maximum reduction rate of 10.36 %, and the maximum reduction rate of power loss coefficient decreased is 11.56 %. At the same time, the particle concentration near the outside and inside wall of the pipe with dune is lower and higher than of without dune, and the particle axial velocities with dune are larger than the case of no dune, and the particle axial pulsation intensity with dune are larger than the case of no dune. Otherwise, the peak value of power spectrum of with dune is lower than that of no dune model in the low frequency region, and the wavelet fluctuation energy of low frequency has a great influence on the axial velocity of particles near the inside wall of pipe for the case of dune model.

Velocimetry of coarse particles in pipeline flow based on GMM model and flow direction constraints

Coarse particle vertical pipeline hydraulic transport has been widely used in deep sea mining, petrochemical industry and shaft slag removal. The precise measurement of the velocity of coarse particles within a solid–liquid two-phase flow in a vertical pipe constitutes a pivotal and challenging aspect when investigating particle motion characteristics. We introduce a method for measuring coarse particle velocity that combines a GMM motion detection model with flow direction constraint matching. In this approach, a high-speed camera system captures the flow image of solid–liquid two-phase flow within a pipeline, and the GMM model analyzes the image to detect the motion particles. Subsequently, a rapid particle matching algorithm, incorporating flow direction constraints, is formulated to establish the particle matching relationships. Simulation and real experiments substantiate the efficacy of this method. Moreover, the method achieves high-precision matching with an accuracy of up to 99%. For videos captured at 30 frames per second (fps), the method enables real-time speed measurement, with an overall measurement error of less than 5%. In summary, this is an effective method for measuring coarse particle velocity field which is important to the study of the motion characteristics of solid–liquid two-phase flow.

Synergy effects of cavitation and particle erosion based on the Erosion/Corrosion Research Center erosion model

This study presents a new synergy model that incorporates the accelerated motion of particles resulting from bubble collapse. The model uses the Erosion/Corrosion Research Center erosion model to predict the combined effect of cavitation and particle erosion on wall surfaces. The results show that, compared with the conventional erosion model, the synergy model reduces the error in the erosion mass loss by up to 24.60%. The significant improvement in prediction accuracy confirms the effectiveness of the synergy model. The severity of sample erosion is positively correlated with the cavitation-inducer angle. The synergy effect leads to an increase in the extent and severity of erosion. Smaller particles demonstrate a more pronounced synergy effect, resulting in significantly accelerated motion and a highly concentrated particle distribution. High erosion rates are associated with high-speed impacts and small-angle impact zones, primarily caused by high-speed cutting erosion. This study presents a novel prediction method for exploring the synergy effect of cavitation and particles on wall erosion and investigates the motion characteristics of particles under this effect.

Numerical Simulation and Experimental Study of Gas–Solid Two-Phase Spraying of Dry Powder Fire-Extinguishing System Based on Fire-Extinguishing Inspection Robot

In order to solve the problem where the traditional intelligent inspection robot only has a single inspection function, we studied the use of a dry powder (including an ultra-fine dry powder) as a fire-extinguishing medium for the first time. In fire-extinguishing robots, the spray pressure is difficult to control, and there are several other issues. For integrated inspection, an intelligent, nitrogen-driven fire-extinguishing robot using a dry powder in a pressure-controlled spray was developed. On this basis, in order to investigate nitrogen-driven dry powder particle spraying as a gas–solid two-phase mechanism, as well as the flow characteristics and the influence of relevant parameters on the spraying effect, a nitrogen-driven dry powder particle spraying system was established as part of a gas–solid two-phase computational fluid dynamics model. The flow field of the spraying system and the particle motion characteristics were analyzed to explore the micro-mechanisms of the influence of different driving pressures, pipe diameters, and nozzle configurations on the spraying of the dry powder. In order to investigate the macroscopic effect of dry powder spraying where the gas–solid two-phase micro-mechanisms could not be revealed, an experimental platform was set up, and the experiments verified the accuracy of the numerical simulation results. We also investigated the dry powder spraying effect under different driving pressures, pipe diameters, nozzle configurations, and loading ratios. Finally, an orthogonal test was designed based on the results of the single-factor experiments to find the best combination of parameters required to achieve the optimal spraying effect. The research results can provide a theoretical and technical reference for the design and development of nitrogen-driven dry powder spraying systems.

Motion of fine particles in a temperature gradient: Experiment, visualization, and numerical simulation studies

The migration and deposition processes of fine particles under the influence of temperature gradients and fluid flow are widely prevalent. Investigating the mechanisms of particle interactions in these processes contributes to the development of efficient dust removal techniques. In this work, experimental and numerical studies of particle motion in temperature gradient fields are conducted. The research encompasses both qualitative and quantitative analyses of particle motion influenced by thermophoresis and particle diameter. Qualitative analysis reveals that the motion characteristics of particles are jointly determined by gravity, drag force, and thermophoretic force, and the diameter range that exhibiting a notable influence of the thermophoretic force is 20–30 μm. Quantitative analysis shows that the manifestations of deposition and diffusion become more evident with an increasing temperature gradient. For instance, in comparison to the working condition with ΔT = 0 K and dp = 20 μm, the deposition mass increases by approximately 23% when ΔT = -15 K; conversely, it diminishes by about 11% when ΔT = 15 K. Additionally, the Discrete Phase Model (DPM) is employed to simulate the motion of gas-solid flow. This study presents a novel visualization system to observe particle motion in gas-solid systems to elucidate the mechanisms underlying the thermophoretic effect and establish a robust theoretical foundation for thermophoretic dust removal technology.

Motion characteristics and wear analysis of particles in the clearances of a twin-screw pump

The rotors of twin-screw pumps would be worn by hard particles for deep-sea oil and gas mixture transport. It led to the destruction of the seal clearance and the deterioration of pump performance. Based on the Euler–Lagrange method and dynamic grid technology, the transient numerical simulation of solid–liquid two-phase flow in a twin-screw pump was carried out and validated by experiment. The motion characteristics of particles in the tip, interlobe, flank clearance, and the causes of rotor wear were clarified. The results revealed that the severe wear at rotor tips was caused by the particles when they enter the tip clearance rather than leaving the tip clearance with the leakage jet flow. Particles passing through the flank clearance had high velocity and contributed to the wear at rotor tips. The main flow in the tooth chamber was disturbed by the interlobe and flank clearance leakage, even resulting in local high-speed reflux near the engagement. With the increase in the particle concentration and diameter, the collision frequency between particles and rotor tips increased, aggravating the risk of wear at rotor tips. The research could reveal the motion nature of particles following the liquid phase and their wear mechanism in twin-screw pumps.

Flow field analysis and particle erosion of tunnel‐slope systems under coupling between runoff and fast (slow) seepage

AbstractThe presence of particles on the surface of a tunnel slope renders it susceptible to erosion by water flow, which is a major cause of soil and water loss. In this study, a nonlinear mathematical model and a mechanical equilibrium model are developed to investigate the distribution of flow fields and particle motion characteristics of tunnel slopes, respectively. The mathematical model of flow fields comprises three parts: a runoff region, a highly permeable soil layer, and a weakly permeable soil layer. The Navier‒Stokes equation controls fluid motion in the runoff region, while the Brinkman‐extended Darcy equation governs fast and slow seepage in the highly and weakly permeable soil layers, respectively. Analytical solutions are derived for the velocity profile and shear stress expression of the model flow field under the boundary condition of continuous transition of velocity and stress at the fluid‒solid interface. The shear stress distribution shows that the shear stress at the tunnel‐slope surface is the largest, followed by the shear stress of the soil interface, indicating that particles in these two locations are most vulnerable to erosion. A mechanical equilibrium model of sliding and rolling of single particles is established at the fluid‒solid interface, and the safety factor of particle motion (sliding and rolling) is derived. Sensitivity analysis shows that by increasing the runoff depth, slope angle, and soil permeability, the erosion of soil particles will be aggravated on the tunnel‐slope surface, but by increasing the particle diameter, particle‐specific gravity, and particle stacking angle, the erosion resistance ability of the tunnel‐slope surface particles will be enhanced. This study can serve as a reference for the analysis of surface soil and water loss in tunnel‐slope systems.

The Study of Structural Optimization on Hydraulic Performance and Anti-Clogging Performance of Labyrinth Drip Irrigation Emitters

The core component of a properly functioning drip irrigation system is the drip irrigation emitter. Irrigation water containing impurities and sand particles can easily lead to clogging of the drip irrigation emitter, reducing the efficiency of the drip irrigation system. In this paper, orthogonal tests were used to optimize the flow channel structure, combined with the computational fluid dynamics–discrete element method (CFD-DEM) to analyze the flow index and sand particle motion characteristics. Clear water tests and short-cycle anticlogging tests were used to validate the results of the numerical simulation, and the relationship between the hydraulic performance and anti-clogging performance was revealed via linear regression. The results showed that the structural parameters of drip irrigation emitters were important factors affecting the flow index and sand movement characteristics. The order from largest to smallest was the turning angle, amount of interdental reference, flow channel depth, flow channel width, and width of the top base. The sand passage rate and the percentage decrease in velocity can be used as important indicators of anti-clogging performance, and there was a negative correlation between the two indicators. The flow channel with a 65° turning angle had the lowest flow index, and the sand passage rate can reach up to 91.48%; the reason was that the main flow region velocity was higher, the vortex region and the sand energy loss were small, which was not easy to clog. The equation for the relationship between flow index and sand passage rate was a negative correlation for drip irrigation emitters between a 65° and 75° turning angle. The drip irrigation emitter with a 65° turning angle had better hydraulic performance and anti-clogging performance.

Research on a new-designed Venturi ejector and dazomet particle motion characteristics for dilute-phase pneumatic conveying systems based on CFD-DEM

To disperse dazomet, a commonly used soil fumigant for soil disinfection, over large soil surfaces, dilute-phase pneumatic conveying can be utilized. Currently, most research has focused on pneumatic conveying systems for large particles, such as coal conveying or pneumatic seeding However, there has been almost no research on the dilute-phase pneumatic conveying of dazomet particles. Therefore, a coupled simulation model based on computational fluid dynamics and discrete element method (CFD-DEM) was established to study the effect of the structural parameters of the Venturi ejector on the motion of particles and airflow fields variation characteristics for the pneumatic conveying system of dazomet particles. Based on the Box–Behnken experimental design method, a 3-factor and 3-level response surface simulation experiment was carried out by selecting the contraction angle, throat diameter, and diffusion angle of the Venturi ejector as factors. The suction-flow ratio, average velocity of particles, average coordinates of particles in the vertical direction, and corresponding standard deviation at the outlet of the pipeline were chosen as response indexes. Multiple linear regression models were established between each factor and response index. The simulation results showed that the impact of factors on the 4 response indexes from strong to weak were throat diameter, contraction angle, and diffusion angle. With decreasing throat diameter, the suction flow ratio and average velocity of the particles increased. The average coordinates of the particles in the vertical direction decreased, while the standard deviation increased, indicating that the pneumatic conveying performance of the system increased. The optimal structural parameters for the contraction angle, throat diameter, and diffusion angle were 34.5°, 15 mm, and 12.0°, respectively. The experimental results demonstrated that the application precisions of the optimised Venturi ejector were 99.23%, 98.46%, and 98.56% at application rates of 15, 20, and 25 g/s, respectively. The results provide a theoretical reference for the structural optimisation of the Venturi ejector and operational performance evaluation of the pneumatic conveying system for dazomet particles.

Particle motion analysis and performance investigation of a fertilizer discharge device with helical staggered groove wheel

Enhancing the uniformity of fertilizer particles flow is crucial in fertilizer discharge device research, and the analysis of particle motion process contributes to improving fertilization performance. In this study, the discrete element method was employed to conduct a phenomenological analysis and numerical investigation of the particle motion characteristics influenced by structural feature parameters of the groove wheel-type fertilizer discharge device. A performance evaluation model based on the uniformity of fertilizer discharge and supplemented by the flow characteristics and mechanical properties of particles was established. The results demonstrated that the particles flow within the fertilizer bin exhibits a recirculating surge induced by the rotation of the groove wheel. The geometric morphology of the outer edge grooves and their spatial distribution along the groove wheel circumference affect the uniformity of fertilizer filling and discharge mass flow rate. The force exerted on the fertilizer particles and their potential breakage are primarily concentrated during the fertilizer compaction stage, while the particles flow forms a convergence due to the sliding of the fertilizer along the discharge slope. After optimization, the discharge CV is reduced from 91.54 % to 31.48 %, and the uniformity is improved by 60.06 %. This study proposes a helical staggered groove wheel fertilizer discharge device structural model, providing new insights for the optimization of agricultural fertilization machinery equipment.

Optical sorting by trajectory tracking with high sensitivity near the exceptional points

Exceptional points (EPs) in non-Hermitian systems embody abundant new physics and trigger various novel applications. In the optical force system, the motion of a particle near its equilibrium position is determined by the optical force stiffness matrix (OFSM), which is inherently non-Hermitian when the particle is illuminated by vortex beams. In this study, by exploiting the rapid variations in eigenvalues and the characteristics of particle motion near EPs of the OFSM, we propose a method to sort particles with subtle differences in their radii or refractive indices based on their trajectories in air. We demonstrate that the trajectory of a particle with parameters slightly larger than those corresponding to certain EPs closely resembles an ellipse. The increase in the major axis of the ellipse can be several orders of magnitude larger than the increase in particle radius. Furthermore, even a slight change in the refractive index can not only significantly alter the size of the ellipse but also rotate its orientation angle. Hence, particles with subtle differences can be distinguished by observing the significant disparities in their trajectories. This approach holds promise as a technique for the precise separation of micro and nanoscale particles.

Dynamic behavior of skyrmion collision: spiral and breath

A magnetic skyrmion is a particle-like topological soliton, which is an ideal candidate for developing high-density storage and logic devices due to its nonvolatility and tunability. In view of the particle motion characteristics of skyrmion, different skyrmions in a material inevitably interact in the form of short-range repulsion and long-range attraction. In this work, the dynamic characteristics of skyrmion collision in a ferromagnetic Co thin film are investigated by using micromagnetic simulations. It is found that the dynamic behavior of skyrmion after collision is highly dependent on the size of the strip, the initial velocity of skyrmion and magnetic damping constant. For the collision of two skyrmions, when the strip width exceeds the critical value, the skyrmions form a pair and rotate counterclockwise in the form of spiral and breath. It is interesting that the rotation and breath of skyrmions keep the same periodicity under the negligible damping, and the frequency increases with the increase of the initial velocity of skyrmion. Further, the collision of a system of three skyrmions reveals that they interact in pairs to form closed periodic trajectories. The results of the present work not only give an insight into the multi-skyrmion dynamics, but also provide guidance for the development of spintronic devices based on multi-skyrmion motion.

Investigating real-time monitoring indices of compaction quality from particle movement characteristics of distinctly-graded unbound aggregate materials subjected to vibratory compaction

The compaction quality greatly affects the in-service performance of unbound aggregate materials (UAMs); however, there still lack real-time, non-destructive, and effective indices for compaction quality assessment. This paper aimed to reveal meso-scale mechanisms of macroscopic vibratory compaction behavior and evaluate compaction quality from particle movement characteristics. A series of newly-developed laboratory vibratory plate compaction tests were conducted on UAM specimens of different gradations. The innovative self-powered, wireless sensors resembling realistic particles (termed as “SR sensors”) were placed inside UAM specimens to monitor three-dimensional (3D) particle accelerations and Euler angles during vibratory compaction. The effects of gradation and vibratory frequency on both macroscopic compaction behavior and meso-scale particle motion characteristics were analyzed. The results show that the entire vibratory compaction process can be divided into three distinct stages according to discernibly-staged particle movement patterns. The degree of compaction (DOC) of UAMs is significantly correlated with two novel particle-motion-based compaction quality indicators.