Particles In Channel Research Articles

Effects of the Resonant Scattering of Channeled Particles with the Generation of Electron and Phonon Excitations

Effects of the Resonant Scattering of Channeled Particles with the Generation of Electron and Phonon Excitations

Inertial effects on rectification and diffusion of active Brownian particles in an asymmetric channel.

Micro- and nano-swimmers, moving in a fluid solvent confined by structures that produce entropic barriers, are often described by overdamped active Brownian particle dynamics, where viscous effects are large and inertia plays no role. However, inertial effects should be considered for confined swimmers moving in media where viscous effects are no longer dominant. Here, we study how inertia affects the rectification and diffusion of self-propelled particles in a two-dimensional, asymmetric channel. We show that most of the particles accumulate at the channel walls as the masses of the particles increase. Furthermore, the average particle velocity has a maximum as a function of the mass, indicating that particles with an optimal mass Mop * can be sorted from a mixture with particles of other masses. In particular, we find that the effective diffusion coefficient exhibits an enhanced diffusion peak as a function of the mass, which is a signature of the accumulation of most of the particles at the channel walls. The dependence of Mop * on the rotational diffusion rate, self-propulsion force, aspect ratio of the channel, and active torque is also determined. The results of this study could stimulate the development of strategies for controlling the diffusion of self-propelled particles in entropic ratchet systems.

Numerical method investigation on the aggregation characteristics of non-spherical particles.

Under the background of the mechanical mechanism research of microfluidic technology for separating and screening pipeline particulate matter, this paper proposes an improved relative motion model by combining the multiple reference frame method and the relative motion model. Worked with a quasi-fixed constant method, this model can numerically calculate the aggregation features of non-spherical particles in the low Reynolds number channels. The results demonstrate that when Re = 40~80, ellipsoids exhibit an aggregation trend similar to circular particles with the same diameter as its largest circumscribed sphere. The aggregation position is affected by the ratio of long and short axes of particles, and the distribution trend is determined by the relative size of these particles. When the channel's Reynolds number is less than the critical Reynolds number, the aggregation position of elliptical particles will be closer to the pipe center with the increase in the Reynolds number, which is contrary to the aggregation tendency of circular particles more proximate to the pipe wall with the increase in the Reynolds number. This finding provides a novel idea and method for further exploring the aggregation rules of non-spherical particles and offers substantial guidance for separating and monitoring pipeline particulate matter via microfluidic technology and other related industrial applications.

Lateral Migration of Variously Shaped Particles: A Computational Study

AbstractThe current work deals with the simulation of lateral migration of differently shaped particles in a straight channel through which fluid flows with a Poiseuille pattern of flow. The immersed boundary method based on feedback force is adopted for the current work. The equilibrium positions and migration times for circular, elliptical, rectangular, square, and biconcave particles are studied and presented. The cases of neutral and massive (high ratio of particle density to fluid density) particles are presented, and in both scenarios the biconcave particle attains its equilibrium position closest to the bottom wall and the elliptical particle acquires its equilibrium position closest to the channel center. Also, the migration time is highest for the biconcave particle, whereas it is lowest for the rectangular particle.

Experimental and Numerical (Fluent-VOF, k-ϵ, DPM) Study of Variation of Trap Efficiency of Irregular Hexagonal SIT (Sediment Invert Trap) for Particle Removal in Rectangular Open Drains and Sewers

At some locations along the length of open sewers and drains, sediment particles get deposited on the bottom bed, reducing hydraulic efficiency. A sediment invert trap (SIT) can be implemented on the bottom of open sewers and drains to trap sediment particles moving on the bed surface. Several investigators have conducted experimental and computational studies to understand the particle trapping behavior of invert traps of various shapes and depths under varying sediment and flow parameters. In experimental studies, previous investigators have used actual and artificial sediment particles; in computational analyses, spherical particles have been considered. The current study investigated the particle trapping behavior of an irregular hexagonal sediment invert trap (SIT) through experiments and two-dimensional (2D) numerical modeling. Seventy-two experiments were performed using actual sewage solid particles in an open rectangular channel with a bottom-fitted invert trap with multiple depths. Sixty numerical simulations were performed using ANSYS Fluent 2020 R1 computational fluid dynamics (CFD) software, considering spherical and nonspherical sewage solid particles. The velocity field was predicted using the volume of fluid (VOF) model combined with the realizable k-ϵ turbulence model. Particle trap efficiency was predicted using a stochastic discrete phase model (DPM). Trap efficiency varied significantly with depth of flow, invert trap depth, slot aperture size, and particle size and shape. Analysis of the simulated flow field showed that variation of turbulent kinetic energy above the trap’s slot aperture was also responsible for variations in trap efficiency values. Fluent simulations considering particles as nonspherical (using shape factors) agreed well with experimentally measured trap efficiency, with mean absolute percentage errors (MAPE) of 6.23%, 8.79%, and 13.77% for particle size ranges SS1, SS2, and SS3, respectively, with both slot apertures at all flow depths. The 2D-CFD study consistently overpredicted trap efficiencies compared to the experimental findings. With a fixed length and width of 0.32 and 0.15 m, respectively, the optimal depth of the irregular hexagonal SIT was found to be 0.65 m with slot aperture sizes of 0.15 and 0.03 m, whereas with slot aperture size of 0.15 m only, invert trap depths equal to 0.58, 0.43, and 0.38 m was found as optimum.

Rotation and separation of chiral active particles in a ring-shaped channel.

Transport of chiral active particles is numerically investigated in a two-dimensional ring-shaped channel. The ring-shaped channel is transversal asymmetric and can induce the directed transport (rotation) of chiral active particles. For the particles with small chirality, they slide along the outer boundary of the channel. For the particles with large chirality, the particles move along some small local circular orbits and can also exhibit directed rotation. Moreover, the rotation effect can be strongly enhanced by modifying the inner boundary geometry. Based on the study of particle rotation, we further study the separation of active particles with different chiralities. It is found that the particles with different chiralities may be distributed in different regions of the ring-shaped channel. Interestingly, these particles can be completely separated by shifting the channel's inner boundary or adding a blocking plate in the channel. Our results may be useful for understanding relevant experimental phenomena and provide a scheme for the separation of binary mixtures.

Directed transport of deformable self-propulsion particles in an asymmetric periodic channel

<sec>Molecular motor can effectively convert chemical energy into mechanical energy in living organisms, and its research is currently at the forefront of study in biology and physics. The dynamic process of its guided movement, along with the crucial role they play in intra-cellular material transport, has significantly aroused the interest of many researchers. Theoretical and experimental researches have allowed detailed examinations of the motion attributes of these molecular motors. The Brownian ratchet model important. It provides an illustration of a non-equilibrium system that transforms thermal fluctuation into guided transport by utilizing temporal or spatial asymmetry. The mechanism has been extensively explored and studied across fields including physics, biology and nanotechnology. Investigations into a variety of ratchets and identification of optimum conditions contribute to a deeper understanding of guided Brownian particle transport.</sec><sec>Preceding studies on ratchet systems largely concentrated on the rectification motions of diverse types of particles-active, polar and chiral-in asymmetric structures. However, the transport of deformable particles in asymmetric channel has not been examined relatively. Particles in soft material systems such as cell monolayer, tissue, foam, and emulsion are frequently deformable. The shape deformation of these soft particles significantly affects the system’s dynamic behavior. Thus, understanding the guided transport of these deformable particles within a confined structure is crucial.</sec><sec>In order to explain this problem more clearly, we numerically simulate the guided transportation of active, deformable particles within a two-dimensional, periodic, asymmetric channel. We identify the factors that influence the transport of these particles within a confined structure. The main feature of the deformable particle model is that the particle’s shape is characterized by multiple degree of freedom. For active deformable particles, self-propulsion speed disrupts thermodynamic equilibrium, leading to guided transport in spatially asymmetric condition. Our findings demonstrate that a particle’s direction of movement is entirely determined by the channel's asymmetric parameter, and it tends to be attracted towards increased stability. Augmenting particle self-propulsion speed and particle softness can facilitate ratchet transport. When the self-propulsion speed <i>v</i><sub>0</sub> is large, the particle’s tensile effect becomes more apparent, and particle softening significantly enhances directed transport. In contrast, an increase in density and rotational diffusion can slow particle rectification. Increased density can obstruct particles, making channel passage more difficult. Elevated rotational diffusion reduces persistence length, challenging particle transition through channels. With constant density, a greater number of particles will also encourage rectification. These research findings offer a valuable insight into the transportation behaviors of deformable particles in a confined structure. They also deliver crucial theoretical support for applicable experiments in the field of soft matter.</sec>

Inertial migration of non-spherical particles in straight microfluidic channels

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

Nuclear data generation & implementation for analog Monte Carlo simulation

Nuclear data is in constant evolution as more experimental data is gathered, computational capabilities increase, and evaluators verify its validity by means of stochastic and deterministic simulations. The focus here is on the analog Monte Carlo simulation of nuclear reactions that produce more than two particles in the outgoing channel, which needs specific considerations to ensure the correlations between the particles and thus the conservation of energy and of translational and angular momenta. It is possible to adapt nuclear data and its exploitation to implement realistic reactions from the phenomenological point of view (as opposed to the historical need of variance reduction techniques), which increases computation time but allows the expansion of the transport codes capabilities. Simulation anomalies were found concerning the kinematical calculations of photon energies emitted from neutron-induced inelastic scattering (n,n’γ), as well as concerning the photon multiplicity of 155Gd(n,γ) due to the presence of a rotational band in 156Gd. Recommendations are given for potential solutions for both anomalies.

Coupling immersed boundary and lattice Boltzmann method for modeling multi‐body interactions subjected to pulsatile flow

This paper numerically investigates the effect of pulsating flow on the settling dynamics of rigid circular particles. This is an interdisciplinary subject and spans several areas ranging from mathematical and numerical modeling to fluid mechanics. For this purpose, pulsatile flow characteristics are embedded in the combination of the direct‐forcing immersed boundary method and the split‐forcing lattice Boltzmann method. Inter‐collision forces between the solid boundaries (particles and boundaries) and the added mass force due to acceleration are considered. Adequate verification tests are done to ensure the credibility of the findings. The critical parameters of pulsating flow, such as amplitude and frequency of pulsation, are investigated in detail. The paper especially puts emphasis on the interaction between particles and studies the well‐known drafting, kissing, and tumbling (DKT) phenomena. Two different scenarios are taken into account and also compared with the stationary flow. The first case is when the pulsating flow is in the direction of gravity (co‐flow), while in the latter, there is an opposing flow (counterflow). The sedimentation manners of 12 particles in a vertical channel are also presented. The findings shed light on the importance of pulsating flow and the extension of the proposed computational method for such problems. It is also revealed that pulsation and its variables can alter DKT by either postponing or speeding up the process. Also, in some cases, the cycle of DKT can be maintained incompletely, and particles would just stick together. The results can be useful for various engineering problems like filtration and particle sorting.

Continuous Particle Aggregation and Separation in Acoustofluidic Microchannels Driven by Standing Lamb Waves

In this study, we realize acoustic aggregation and separation of microparticles in fluid channels driven by standing Lamb waves of a 300-μm-thick double-side polished lithium-niobate (LiNbO3) plate. We demonstrate that the counter-propagating lowest-order antisymmetric and symmetric Lamb modes can be excited by double interdigitated transducers on the LiNbO3 plate to produce interfacial coupling with the fluid in channels. Consequently, the solid-fluid coupling generates radiative acoustic pressure and streaming fields to actuate controlled acoustophoretic motion of particles by means of acoustic radiation and Stokes drag forces. We conducted finite-element simulations based on the acoustic perturbation theory with full-wave modeling to tailor the acoustic and streaming fields in the channels driven by the standing Lamb waves. As a result, the acoustic process and the mechanism of particle aggregation and separation were elucidated. Experiments on acoustic manipulation of particles in channels validate the capability of aggregation and separation by the designed devices. It is observed that strong streaming dominates the particle aggregation while the acoustic radiation force differentially expels particles with different sizes from pressure antinodes to achieve continuous particle separation. This study paves the way for Lamb-wave acoustofluidics and may trigger more innovative acoustofluidic systems driven by Lamb waves and other manipulating approaches incorporated on a thin-plate platform.

Motional characteristic and impact of fiber particles in the impeller of a centrifugal pump

A centrifugal pump whose open impeller was made of polycarbonate was adopted to explore the influence of different concentrations of slender fiber particles on the external characteristics of the pump and to obtain the motional characteristics of the particles in the channels of the impeller. The external characteristics of the pump were used to determine the performance of the pump. A high-speed photographic system was used to analyze the motion of fiber particles in the channels of the impeller. Changes in the head and efficiency of the pump and changes in the distribution of fiber particles in impeller channels were obtained under different concentrations of fiber particles and different flow rates of fiber suspensions. The head associated with the transport of a fiber suspension whose mass concentration of fiber particles was 0.15% and the head associated with the transport of a fiber suspension whose mass concentration of fiber particles was 0.30% did not differ greatly from the head associated with the transport of clean water. However, compared to the transport of clean water, the transport of the fiber suspensions improved the efficiency of the pump. When the pump transported the fiber suspension whose mass concentration of fiber particles was 0.30%, on average, the efficiency of the pump increased by 8.49%. When the flow rates of the fiber suspensions increased, the uniformity of the distribution of the particles increased. When entering the impeller, a small number of fiber particles showed rotating and flapping motions. However, the motions gradually disappeared as the particles left the impeller. At a constant radius (i.e., 75% and 95% radius, respectively), the velocity profile increased gradually when the mass concentration of fiber particles increased from 0.1% to 0.15%. It is manifest that fiber suspension undergoes less flow loss as the mass concentration of fiber particles increases.

Hierarchical Quantum Information Splitting of an Arbitrary Two-Qubit State Based on a Decision Tree

Quantum informatics is a new subject formed by the intersection of quantum mechanics and informatics. Quantum communication is a new way to transmit quantum states through quantum entanglement, quantum teleportation, and quantum information splitting. Based on the research of multiparticle state quantum information splitting, this paper innovatively combines the decision tree algorithm of machine learning with quantum communication to solve the problem of channel particle allocation in quantum communication, and experiments showed that the algorithm can make the optimal allocation scheme. Based on this scheme, we propose a two-particle state hierarchical quantum information splitting scheme based on the multi-particle state. First, Alice measures the Bell states of the particles she owns and tells the result to the receiver through the classical channel. If the receiver is a high-level communicator, he only needs the help of one of the low-level communicators and all the high-level communicators. After performing a single particle measurement on the z-basis, they send the result to the receiver through the classical channel. When the receiver is a low-level communicator, all communicators need to measure the particles they own and tell the receiver the results. Finally, the receiver performs the corresponding unitary operation according to the received results. In this regard, a complete hierarchical quantum information splitting operation is completed. On the basis of theoretical research, we also carried out experimental verification, security analysis, and comparative analysis, which shows that our scheme is reliable and has high security and efficiency.

Effect of channel width on the sedimentation modes of a cold elliptical particle in hot narrow channels

Many natural and industrial processes involve transport of solid particles. This research reports sedimentation modes of a single cold elliptical particle with an aspect ratio of 2 in narrow hot channels. Prior research on settling of non-isothermal elliptical particles was limited to wide vertical channels. A cold particle with constant non-dimensional temperature of T p ∗ = 0 and an initial orientation of θ 0 = π / 3 between its major axis and horizontal axis is released in a hot fluid. Fluid Prandtl number is 7, and its initial temperature is T f , 0 ∗ = 1 . Simulations are based on an in-house lattice-Boltzmann solver with two distribution functions for fluid flow and heat transfer and using Boussinesq approximation in low density variations. In total, 120 simulations in five channel widths have been run, with enough time for the particle to reach a distinct sedimentation/rising pattern. Effects of channel width ( L = 12 A / 13 − 38 A / 13 ), where A is ellipse major diameter, the Grashof number ( Gr = 100 − 1000 ), and particle-to-fluid density ratio ( ρ r = 1 . 0003 − 1 . 3 ) have been studied. Channel width, gravity and heat transfer have been discovered to cause the particle to travel up or down. Seven sedimentation modes have been observed including i) horizontal at centerline, ii) inclined off-center, iii) vertical at center, iv) oscillatory motion around centerline, v) tumbling off-center, vi) horizontal fluttering at centerline, and vii) inclined off-center with oscillations. Three of these patterns (iii, iv, vii) are peculiar to narrow channels, and have not previously been observed for cold elliptic particles in wide channels ( L = 52 A / 13 ). Moreover, the particle has been seen to move upward rather downward in the narrowest channel for small particle-to-fluid density ratios. • Sedimentation modes of a cold elliptical particle in hot narrow channels are studied. • In total seven settling modes are observed; three of them are new and unique to narrow channels. • Grashof and Archimedes number and channel width have significant influence on the sedimentation pattern. • In narrow channels, wall and heat transfer effect are stronger than in wide channels and can even push the particle upward by overcoming the gravity. • Sedimentation velocity of the particle has been seen to be lower in narrow channels compared to wider ones.

Numerical study of microscopic particle arrangement of suspension flow in a narrow channel for the estimation of macroscopic rheological properties

In a narrow channel, the apparent relative viscosity of a suspension with finite-size particles is strongly dependent on its microscopic particle arrangement. Relative viscosity increases when suspended particles flow near the channel wall; thus, a suspension in a narrow channel does not always exhibit the same rheological properties even if the concentration is the same. In this study, we focus on the inertia and concentration of particles in a narrow channel and consider their effects on the microscopic particle arrangement and macroscopic suspension rheology. Two-dimensional pressure-driven suspension flow simulations were performed using a two-way coupling scheme, and normalized particle density distribution (PDD) were implemented to consider their particle arrangements. The results demonstrated that the velocity profiles for the particle suspension were changed by the Reynolds number and particle concentration because of the interactions between particles according to the power-law index. These changes affected the particle equilibrium positions in the channel, and the subsequent changes in solvent layer thickness caused changes in the macroscopic apparent viscosity. The behavior of microscopic particles played important roles in determining macroscopic rheology. Thus, we have confirmed that a normalized PDD can be used to estimate and assess the macroscopic rheology of a suspension.

Dynamics of landslide-generated tsunamis and their dependence on the particle concentration of initial release mass

Tsunamis are impulse water waves generated at the moment when rapidly moving landslide or any other gravitational mass strikes a water reservoir by transforming its impact energy to the water body. The propagation of resulting water waves might cause damages and casualties nearby field as well as in farther coast. The destructive effects caused by the landslide-generated impulsive waves can be significantly affected by the characteristics of channel geometry and particle concentration of initial mass. Experimental and computational models have been substantially applied to study the dynamics of these complicated natural events. Using a general two-phase mass flow model, we conduct various numerical experiments and then illustrate the high-resolution simulated results in geometrically three-dimensional framework for time evolution of both solid and fluid wave structures with varying concentrations of the two-phase initial release mass. The results reveal that amplitudes of tsunami and the run-out extents are quickly expanding along down-slope and cross-slope when the solid concentration of initial landslide mass is increased. The concentration of grains in the release mass significantly affects the flow dynamics and fluid waves when the flow hits a still reservoir downstream. The outcomes indicate that the numerical modeling using advanced governing equations, and integrated simulation techniques can be used to assess the different geophysical mass flow dynamics such as granular flow, debris flow, mud flow, and flash flood as well as GLOF and the dynamics of water waves and submarine flow after the flow-reservoir-interaction. The study of the influence of the particle concentration of initial landslide mass can be applicable to mitigate the hazards caused by tsunamis and submarine mass movements.

Wrap-around sensors for electrical detection of particles in microfluidic channels

Microfluidic devices with integrated electrical sensors have been widely employed in the detection and characterization of particles suspended in liquids. Conventionally, electrical sensors in microfluidic devices are composed of electrodes all patterned on the same surface in a coplanar arrangement. While simplifying the fabrication of electrical sensors within microfluidic channels considerably, the use of coplanar electrodes leads to non-uniform electric fields within the channel and complicates scaling of electrical sensor networks by constraining the routing of different traces within the same plane. The alternative of integrating counter-facing parallel electrodes into microfluidic channels to alleviate those limitations requires a complex fabrication process. In this work, we present a robust and straightforward approach to creating 3D electrical sensors in microfluidic devices fabricated using soft lithography. By placing a blanket electrode on the microfluidic channel walls, our electrical sensor wraps around the flow channel to (i) provide higher sensitivity than their coplanar counterparts, (ii) extend the sensing volume beyond the vicinity of a surface and (iii) simplify the creation of electrical sensor networks with complex geometries by relaxing the routing constraints on traces. Practical implementation of 3D electrical sensors in microfluidic channels offers the potential to enhance the utility of electrical sensing without impacting the frugality of fluidic components in designing integrated microfluidic systems as quantitative platforms.

Investigating pair-production by Breit–Wheeler process in a collisional plasma

Positrons have many potential applications in the field of high-energy nuclear and particle physics. For the generation of such high-energy positrons, we propose a mechanism via an interaction of optical vortex laser beams with collisional plasma. Based on the multiphoton Breit–Wheeler mechanism, the production of electron–positron pairs shows to be strongly dependent on the energy associated with the synchrotron radiation. Such radiations are emitted by accelerated charged particles in the plasma channel under quasistatic spontaneous magnetic field that confines the motion of the electrons. For the precise regulation of the accelerated positrons important quantities such as the probabilistic generation of positrons and the angular momentum of the plasma electrons are evaluated and discussed. It is observed that the use of the incident Laguerre–Gaussian laser beam helps to generate on-axis sheath formation to focus and accelerate the produced positrons.

Improvement of accuracy of under-performing classifier in decision making using discrete memoryless channel model and Particle Swarm Optimization

In-spite of availability of wide range of algorithms for constructing multi-class classifier, there are applications like Decision support system, Game prediction in the sports, where the multi-class classifier performs relatively poor in terms of achieving the reasonable classification accuracy. In this paper, poorly performing multi-class classifier (constructed using the classical methods like Artificial Neural Network, cascade of Support Vector Machine, etc.) is treated as the discrete memoryless channel model with known transition probabilities (channel matrix) and the unknown priors. It is further used to construct M-ary Mini-Max technique based randomized decision rule to improve the performance of the multi-class classifier in terms of the classification accuracy. The prior probabilities and the probabilities associated with the M-ary randomized decision rule are further solved using the Particle Swarm Optimization. The experimental results based on the Monte-Carlo simulation using the synthetic data set and the real data set reveal the consistent improvement in the performance of the poorly performing classifier using the proposed technique.

Diffusiophoretic Movements of Polystyrene Particles in a H-Shaped Channel for Inorganic Salts, Carboxylic Acids, and Organic Salts.

Diffusiophoresis is the movement of particles as a result of a concentration gradient, where the particles can move toward higher concentrations. The magnitude of the movement is largest for the electrolyte solute and depends upon the relative concentration gradient, surface potential, and diffusivity contrast between the cation and anion. Here, diffusiophoresis of ordinary polystyrene particles is studied in a H-shaped channel for different solutes. The experimental results are compared to a numerical model, which is solely based on the concentration gradient, surface potential, and diffusivity contrast. The surface potential of the particles was measured to use as input for the numerical model. The diffusiophoretic movement of the experiments aligns well with the theoretical predicted movement for the inorganic (lithium chloride and sodium bicarbonate) and organic (lithium formate, sodium formate, and potassium formate) salts measured. However, for the carboxylic acids (formic, acetic, and oxalic acids) measured, the theoretical model and experiment do not align because they are weak acids and only partially dissociate, creating a driving force for diffusiophoresis. Overall, the H-shaped channel can be used in the future as a platform to measure diffusiophoretic movement for more complex systems, for example, with mixtures and asymmetric valence electrolytes.