Particle Motion Patterns Research Articles

Molecular Origins of Long-Term Changes in a Competitive Continuous Biosensor with Single-Molecule Resolution.

Biosensing by particle motion is a biosensing technology that relies on single-molecule interactions and enables the continuous monitoring of analytes from picomolar to micromolar concentration levels. However, during sensor operation, the signals are observed to change gradually. Here, we present a comprehensive methodology to elucidate the molecular origins of long-term changes in a particle motion sensor, focusing on a competitive sensor design under conditions without flow. Experiments were performed wherein only the particles or only the surfaces were aged in order to clarify how each individual component changes over time. Furthermore, distributions of particle motion patterns and switching activity were studied to reveal how particle populations change over timespans of several days. For a cortisol sensor with anticortisol antibodies on the particles and cortisol analogues on the sensing surface, the leading hypotheses for the long-term changes are (i) that the particles lose antibodies and develop nonspecific interactions and (ii) that analogue molecules dissociate from the sensing surface. The developed methodologies and the acquired insights pave a way for realizing sensors that can operate over long timespans.

Experimental study on particle movement and erosion behavior of the elbow in liquid–solid flow

Recent investigations into the erosion of elbow junctions predominantly focus on identifying and predicting peak erosion points. Notably, these studies rely heavily on computational fluid dynamics methods, a valid approach but limited by its lack of empirical physical data. Additionally, the majority of these studies concentrate on the extrados, or outer curve of the elbow, neglecting the intrados or the inner curve. To provide a more comprehensive understanding of particle movements and the micro-mechanics of erosion on the elbow intrados, this study utilizes advanced observational technologies. High-speed camera technology, coupled with scanning electron microscopy, is employed to capture and record particle motion and micro-erosion patterns. The erosion rate is then estimated via the weight-loss method. The findings suggest that in low-speed liquid–solid flows (2.5 m/s), particles released from the intrados side of the elbow inlet exhibit a significant trajectory deviation from the centreline at an elbow angle of 60° from the inlet. Particles released from the extrados deviate towards the intrados side at an elbow angle of 30°. Secondary flow contributes to particle acceleration, unexpected trajectory deviation within the elbow, and an upward inclination in erosion on the intrados. The presence of partially overlapping scratches and cracks suggests that continuous ploughing and material fracturing are significant contributors to the micro-mechanics of erosion. When comparing the intrados and extrados, the extrados exhibits longer and shallower scratches, indicating a smaller impact angle. This research provides a more comprehensive understanding of particle trajectories and erosion patterns within elbow junctions during liquid–solid flows, offering new insights into the mechanisms underpinning these processes.

The movement pattern of particles on the surface of liquid marble during rupture based on the DIC algorithm

The stability of liquid marbles is critical to their application in sensors, microfluidic control, microreactors, and other fields. A more comprehensive understanding of the rupture kinetics of liquid marble is instructive for studies in improving the stability of liquid marble. However, the mechanism of rupture of liquid marbles is not clear at present, therefore, this paper addressed this issue by calculating the displacement of particles on the surface of a liquid marble using the DIC (Digital Image Correlation) algorithm. The distribution characteristics of the particles on the surface of the liquid marble and their movement patterns were clarified, the causes of cracks on the marble surface were analyzed, the mechanism of liquid marble rupture was derived, and the effect of volume on rupture kinetics was analyzed. Based on the obtained data, a method was proposed to control the maximum compression that the liquid marble can withstand by spraying different sizes of superhydrophobic coatings. This paper contributes to the study of the stability of liquid marble, allowing its wider application in industrial production.

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.

Erosion mechanism for submarine pipeline on graded sediments using a coupled PORO-CFD-DEM model

To investigate the meso-mechanism of scouring process, a numerical model that couples the porous medium model, computational fluid dynamics and discrete elements method (PORO-CFD-DEM model) is established and validated. Two pipeline conditions, suspended and partially buried, are considered. The porous medium is used to replace most of the discrete elements, significantly reducing the computational requirements. Two particle generation methods, namely fictious grid method (FGM) and breath-first search method (BFM), are proposed, and three kinds of particle samples are generated with different gradations: Gaussian, gap and continuous. Detailed analyses of flow, fluid-particle interaction and sediment motion is conducted with an increasing inlet velocity. When the pipeline is suspended, the seepage flow is induced by the gap flow beneath the pipeline, with the pressure dropping along the seepage path. Around partially buried pipeline, the seepage flow is much weaker and the pressure concentration appears. The seepage force fluctuates, and the loose bed is disturbed, leading to randomly collapses. Different particle movement patterns, including the jumping, suspended transportation and the formation of sand slope, are captured during the simulations. It’s confirmed that the PORO-CFD-DEM model can capture the meso-movement of the particles and provides insights into the theory of sediment transportation.

Fast Fluid Simulation via Dynamic Multi-Scale Gridding

Recent works on learning-based frameworks for Lagrangian (i.e., particle-based) fluid simulation, though bypassing iterative pressure projection via efficient convolution operators, are still time-consuming due to excessive amount of particles. To address this challenge, we propose a dynamic multi-scale gridding method to reduce the magnitude of elements that have to be processed, by observing repeated particle motion patterns within certain consistent regions. Specifically, we hierarchically generate multi-scale micelles in Euclidean space by grouping particles that share similar motion patterns/characteristics based on super-light motion and scale estimation modules. With little internal motion variation, each micelle is modeled as a single rigid body with convolution only applied to a single representative particle. In addition, a distance-based interpolation is conducted to propagate relative motion message among micelles. With our efficient design, the network produces high visual fidelity fluid simulations with the inference time to be only 4.24 ms/frame (with 6K fluid particles), hence enables real-time human-computer interaction and animation. Experimental results on multiple datasets show that our work achieves great simulation acceleration with negligible prediction error increase.

Research on the wear characteristics of magnetorheological fluid in sealing interface considering the interaction between surface roughness and magnetic particles

In this paper, the influence of magnetorheological fluid (MRF) on the wear mechanism of sealing pairs under different surface roughness is studied from the perspective of theoretical analysis and experimental verification. Simulation analysis shows that the coupling of roughness and microparticles changes contact pressure and frictional stress distribution on O-ring acted by asperities. Combined with wear morphologies, it is further proved that roughness affects the movement pattern of particles in the sealing gap, thereby determining the tribodynamic behavior of MRF. Specifically, the roughest sample shows low friction coefficient and best wear resistance, while the smoothest sample exhibits worse tribological performance. The above analysis is the reason for the sealing wear under MRF is completely opposite to that of base oil.

3D Virtual reconstruction of asphalt mixture microstructure based on rigid body dynamic simulation

ABSTRACT This paper presents a virtual generation method for the heterogeneous microstructure of asphalt mixtures. The coarse aggregates used in the digital asphalt mixture were derived from real aggregates captured by a three-dimensional (3D) laser scanner. Then, a rigid-body dynamic simulation framework was proposed to generate a stable skeletal structure composed of coarse aggregates similar to those formed by compaction. Furthermore, FAM and air voids were generated based on the generated aggregate skeleton and the assumption of equal thickness of FAM film. To prove the reliability of the model, the air voids of the digital asphalt mixture samples were verified by comparison with real specimens. The generated digital specimens were also applied to finite element method (FEM) simulations to predict the dynamic modulus of the asphalt mixture and the simulated results were in good agreement with the experimental results. The method can be applied to study the spatial distribution of asphalt mixture components, the movement pattern of aggregate particles during compaction and numerical simulations at the microscopic scale.

Turbidity currents propagating down an inclined slope: particle auto-suspension

The turbidity current (TC), a ubiquitous fluid–particle coupled phenomenon in the natural environment and engineering, can transport over long distances on an inclined terrain due to the suspension mechanism. A large-eddy simulation and discrete element method coupled model is employed to simulate the particle-laden gravity currents over the inclined slope in order to investigate the auto-suspension mechanism from a Lagrangian perspective. The particle Reynolds number in our TC simulation is$0.01\sim 0.1$and the slope angle is$1/20 \sim 1/5$. The influences of initial particle concentration and terrain slope on the particle flow regimes, particle movement patterns, fluid–particle interactions, energy budget and auto-suspension index are explored. The results indicate that the auto-suspension particles predominantly appear near the current head and their number increases and then decreases during the current evolution, which is positively correlated with the coherent structures around the head. When the turbidity current propagates downstream, the average particle Reynolds number of the auto-suspension particles remains basically unchanged, and is higher than that of other transported particles. The average particle Reynolds number of the transported particles exhibits a negative correlation with the Reynolds number of the current. Furthermore, the increase in particle concentration will enhance the particle velocity, which allows the turbidity current to advance faster and improves the perpendicular support, thereby increasing the turbidity current auto-suspension capacity. Increasing slope angle will result in a slightly larger front velocity, while the effect of that on the total force is insignificant.

Investigation of Movement and Deposition Behaviors of Solid Particles in Hydraulic Water Reservoir via the CFD-DEM Coupling Method

Solid contamination existing as solid particles in power fluid transmission systems may lead to transmission performance reduction, system failures, and component damage. The hydraulic reservoir will deposit the contamination and store hydraulic fluid. To investigate its purification ability for solid contamination, experiments and simulations for the motion and deposition status of the typical hydraulic system particles are carried out to reveal the interaction of particles and fluid in hydraulic water reservoirs. The results show that the CFD-DEM coupling method could predict the accurate deposition position of iron particles and sand particles when ignoring the small-scale turbulence effect in the flow field. Besides, the particle motion traces and deposition patterns in the reservoir illustrate that the flow development on the bottom surface results in the particles turning, and particles tend to settle in the low flow energy position. The motion of particles is also linked to particles Stokes number, and the same-size sand particles are easily driven by the fluid. The contribution of this paper could provide a guide for predicting the particle motion and deposition pattern in the hydraulic reservoir.

Experimental and numerical study on the acoustic coagulation of charged particles

Coagulation technology is widely used as a dust removal technology pre-treatment. The mechanism of particle coagulation and charging under the coupling of the electric field and the acoustic field is investigated in this paper. The movement law of the acoustic field waveform, sound pressure level and acoustic field flow rate parameters on the particles are analyzed numerically using COMSOL Multiphysics software, and the operating parameters for the best coagulation effect of charged particles are obtained through experimental studies. The results show that the higher the supply voltage, the more the particles are charged and the better the particle coagulation effect. The higher the sound pressure level, the better the particle coagulation effect. The acoustic frequency is not linearly related to the particle coagulation efficiency. An optimal operating parameter is obtained. The acoustic and electric field coupling resulted in a particle reduction rate of 0.62 and a significant particle coagulation effect. • The mechanism of particle coagulation under the coupling effect of acoustic and electric fields is studied. • The effect of different acoustic field parameters on the particle motion pattern in the furnace is simulated. • The optimal acoustic field parameters are obtained. • The particle reduction rate reaches 0.62.

Seepage Characterization Based on Sandstone Particle Motion Pattern: A Case Study of the TIII Reservoir in the Sangtamu Oilfield

In order to finely characterize the physical properties and seepage characteristics of underwater distributary channel sand bodies in a braided river delta, the particle size distribution, mercury injection, and withdrawal of low, medium, high, and extra-high permeability core samples from the TIII reservoir from 15 core wells in the Sangtamu Oilfield were compared. The pore-throat characteristics of the rocks with different deposition modes and their effects on the fluid seepage were analyzed from the perspective of the deposition processes. The statistical results revealed that the rocks formed in a continuous and stable strong hydrodynamic environment were coarse grained. The seepage capacities of the rock increased as the maximum throat radius connecting with the pores increased. The mercury withdrawal efficiency decreased as the difference between the throat radius and pore radius increased. The percentage of the throat volume without effective seepage to the total volume of the pore-throat system increased as the permeability of the samples increased. Therefore, when characterizing reservoirs based on the porosity and permeability, it is important to differentiate the energy of the hydrodynamic depositional environment of a monogenic sand body in order to improve the accuracy of the understanding of the reservoirs.

MOVEMENT OF A PARTICLE BY A MOVING VERTICAL AUGER BOUNDED BY A CASING

During the various technological operations in various fields of industry and production, the working bodies of machines and tools interact with particles of technological material. At the same time, the geometric shape of the surface of the working bodies determines the character of the movement of particles on it. Particles of the technological material are often considered as material particles, which is acceptable because of their small dimensions. In this case, inertial forces from the rotation of the material are not taken into account, and as a result, the obtained analytical dependencies of its movement are somewhat approximate, however, it can be applied to a certain extent to the material and determine the direction of further research. A fairly common method of transporting technological material is the use of screws – a curved blade in the form of a strip of a helical conoid. Usually, a screw is moving and limited by a stationary coaxial cylindrical casing. In the article, the movement of a particle inside the vertical structure, which is made up of a cylinder and a coaxial strip of a helical conoid, and which rotates around a common vertical axis, is investigated. The differential equations of the relative movement of the particle along the periphery of the screw have been received. A special case, when the surfaces are stationary, was considered. A qualitative analysis of the obtained equations was made and based on this, the patterns of particle movement along the helical line – the curve of the intersection of the screw with the cylinder – were found. Constructive and kinematic parameters, when the particle moves up during sliding along a helical line or falls down, were found. It was established that if the angle of rising of the curve of the intersection of the limiting cylinder with the surface of the screw is less than or equal to the angle of friction of the particle on it, then the movement of the particle in both directions becomes impossible. This applies to both moving and stationary surfaces. The relative and absolute trajectories of particle movement are constructed in the article.

Fluid Dynamics and Numerical Simulation of Exhaled Droplets Containing Infectious Viruses

Understanding the movement and transmission patterns of airborne particles is very important to understand the diseases they carry. One of the most common sources of viral infections is sneezing and coughing. This topic explores the theoretical properties of airborne microbes and their dispersal. It aims at developing a model that can predict the movement and transmission of these particles. The model is formulated using the Runge–Kutta (RK) algorithm, which is a 4th-order standard for solving differential equations. It is used to study the effects of various factors such as wind speed and jet velocity on the movement of droplets. The model is compared to the well-known Maxey–Riley equation. It then explains the various factors that influence the dispersal of airborne microbes. The evaporation of airborne microbes has a significant effect on the movement of smaller particles.

Transport modes of inertial particles and their effects on flow structures and heat transfer in Rayleigh–Bénard convection

We investigate the flow characteristics and kinetic behaviors of particles in turbulent Rayleigh–Bénard convection particulate flows. Direct numerical simulations combined with a Lagrangian point-particle strategy were carried out in the range of Stokes numbers 2×10−4≤StL≤7.3×10−2 for Rayleigh numbers from 2×106 to 108 at the Prandtl number Pr=0.678. A two-way coupling model is employed in which the momentum exchange between the dispersed particles and the carrier fluid is taken fully into account. Based on various patterns of particle motion, we find three transport modes of inertial particles which are labeled as the circling transport (CCT) mode, the channel transport (CNT) mode, and the downpour transport (DPT) mode, respectively. These modes can switch to each other when Stokes numbers and Rayleigh numbers vary and exhibit different effects of particle motions on the flow field and heat transfer. For the CCT and DPT modes, compared with the CNT, a weakening alteration of flow structures and thermal plumes leads to no significant effect on the transport of momentum and heat. For the CNT mode, a pronounced effect of particles on enhancements of the turbulent momentum transport and heat transfer relates to the strong interaction between the particle clusters and the chaotic structures of eddies. What is more, the particles tend to homogeneously distribute for the CCT and DPT modes, although the particles exhibit different transport states. As for the CNT mode, under both preferential sweeping and centrifugal effects, particles accumulate into clusters that hover toward the region of high strain rate and the edges of eddies. We found that the averaged particle settling speeds are almost proportional to the Stokes number. The particle settling speeds are larger than the terminal velocity of Stokesian particles for the CCT and CNT modes as particles tend to settle in the downward fluid. In contrast, it becomes smaller than the terminal velocity for the DPT mode due to the drag of the upward fluid.

CFD modeling of particle dispersion behavior in the MIKE 3 apparatus

A simulation investigation on the flow domain and particle movement pattern in the dispersion stage of dust explosion experiment were conducted using CFD simulation based on Euler–Lagrange approach. A new solver that couples two phases was developed based on the default solver rhoPimpleFoam from the OpenFOAM tool kit. Three sizes of particles 25 μm, 125 μm and 250 μm were simulated and studied. The simulation results of dust front propagation were evaluated by the experiment data. Particles with smaller diameters tended to move slower. Due to the high turbulence, flow vortices in the lower part of the dispersion domain were identified. These vortices gradually became larger with time and the decrease of inflow velocity. Uneven distribution of particles along with the equipment and high concentration of particles between the discharge electrodes were found in the simulation. Furthermore, particles with higher velocity favored the middle position in the tube. These facts suggested that the ignition delay time for particles larger than 125 μm should be higher than 60 ms.

Fully-resolved simulations of an ellipsoidal particle settling in a Bingham fluid

Despite many particle shapes and motion patterns that can be present in viscoplastic settling, the scientific studies are mostly limited to spherical particles and cases in which the solid body motion is purely vertical or rotational. Here we tackle the problem of an ellipsoidal particle settling in Bingham fluid through fully-resolved simulations. Oblate and prolate spheroids of varied aspect ratios and initial orientations are analyzed. We use the Lattice Boltzmann Method (LBM), in which the Bingham constitutive equation is solved exactly. We employ the Immersed Boundary Method (IBM) to delineate the particle boundaries and enforce the no-slip condition over them. For the case of creeping flow around a settling ellipsoid, we benchmark results of the critical yield number for oblate and prolate spheroids against augmented Lagrangian method (ALM) data and provide values for different aspect ratios and initial orientations. Then, we analyze the dynamics of prolate and oblate spheroids settling in Bingham fluid at an inertial flow. We present the evolution of trajectory, orientation, angular momentum, Reynolds number, and drift angle for various aspect ratios and initial orientations.

Numerical simulation on interaction process between impact penetrator and lunar soil particles for lunar subsurface exploration

Unmanned in-situ exploration is an important technique to study the physical and mechanical parameters of lunar composition and evolution. The impact penetrator is an effective device for in-situ detection of the lunar soil profile at predetermined depth. Because of the lack of real lunar soil samples, it is very difficult to study and evaluate the performance of the impact penetrator. In order to truly reflect the interaction between the impact penetrator and lunar soil particles, a simulation model of the lunar soil body was established by means of discrete-element analysis, and the model parameters were matched and verified by the experimental method. Based on this model, the interaction behaviors between the penetrators with different head configurations and the lunar soil body were simulated. The stress field distribution in the lunar soil body and particle movement patterns during the penetrating process were revealed, which reflects the working principle and performance of the penetrator. The numerical simulation on the interaction process between the impact penetrator and lunar soil particles provides a feasible and effective method for the design and optimization of the penetrator, which will contribute to the development of lunar subsurface in-situ exploration technologies.

Simulation and Analysis on Motion Behavior of Metal Particles in AC GIL

Metal particle contamination can seriously affect the reliability of gas-insulated metal enclose transmission line (GIL) and cause insulation failure. In this article, we investigate the metal particle motion patterns based on the entity model of GIL by using finite element simulation. Analysis of motion characteristics of metal particles at different GIL locations is presented based on the charged mechanism and dynamic equation. The impacts of particle attributes, applied voltage, and shielding electrode on motion characteristics are studied. It is found that under ac voltage, the metal particles on the concave and convex sides basically move toward the insulation components. When the metal attributes are different, the size and density of particles dominate the motion pattern under the same voltage. The research observations also indicate that a higher value of applied voltage facilitates the particle to reach the insulator surface while a higher frequency inhibits the particle movement and increases the number of collisions at the ground electrode. Furthermore, the shielding shape affects the electric field distribution, which in turn changes the motion characteristics of particles. Accordingly, the strategy of voltage withstand test and the improved scheme of particle collector are discussed and suggested. This work provides a valuable basis and reference for metal particle control and will guide the design of particle collectors in ac GIL.

Numerical investigation of movement patterns of particles falling in a viscous fluid

To study the movement patterns of particles, the long-term sedimentation of multiple circular particles in a narrow channel filled with a viscous fluid is investigated numerically. The attention is focused firstly on the equilibrium movement pattern of particles at an intermediate terminal Reynolds number (Ret), and then on its connection with behaviors of multiple particles. For three particles released in a symmetric pattern, at the first stage, all particles tend to fall at the same speed, then after a dramatic interaction, particles split into two groups (1 + 2). The single particle moves steadily with a faster velocity along the central line, while the other two particles self-organize into a two-particle system, moving as a steady oblique doublet, periodic oscillation pair, or a steady symmetrical doublet. For the sedimentation of six particles, there are more separations after the first stage. The small groups owning 1, 2 and 3-particle move in their own typical equilibrium movement patterns. It seems that at intermediate Reynolds numbers multiple particles tend to break up into small groups that can maintain their own equilibrium movement patterns. It is shown that the study on the movement patterns of one/two particles can provide essential information for the self-organization behavior of multiple particles.