Particles In Channel Research Articles

Fully developed flow of a higher-gradient nanofluid in a vertical channel: Mixed and natural convection

In the present work, we study the steady Poiseuille flow and heat transfer of a viscous fluid containing nano-sized particles in a vertical channel. The two walls of the infinitely long channel are kept at different constant temperatures. Particles and fluid may have different densities, and account is taken of the thermal expansivity of the fluid by invoking the Boussinesq approximation.The momentum equation describing the fluid differs from the Navier–Stokes equations by containing a bi-Laplacian term of the velocity, as proposed by Fried and Gurtin. The higher-order terms in the momentum equation require additional boundary conditions (strong, weak, general adherence). Several velocity profiles are presented also for real nanofluid suspensions. The found velocities are compared with the velocity of nanofluids relative to the Buongiorno model.

The Impact of Flow Channel Structural Parameters on Both the Hydraulic Performance and Anticlogging Abilities of Variable Flow Emitters

Variable flow emitters are used in subsurface drip irrigation to address challenges in soil moisture transport. This study investigates the impact of flow channel structural parameters on the hydraulic performance and anticlogging ability of emitters using computational fluid dynamics (CFD) simulations and experimental tests. The results show that the realizable k–ε turbulence model can be used to simulate the flow field inside the variable flow emitter flow channel. The nRMSE between the measured (qm) and simulated (q) values of the flow rate is 11.23%, and the relative error between the measured (xm) and simulated (x) values of the flow index is 4.66%, which gives a high simulation accuracy. A polar analysis shows that the tooth angle (A) has the smallest effect on the effluent flow rate at 0.1 MPa (q0.1), x, and particle passage rate (η) of the variable flow emitter. Flow channel depth (D), tooth spacing (B), and tooth height (E) have a different order of precedence in the influence of the three indices, which are D > B > E > A, B > E > D > A and E > B > D > A, respectively. The value of η is positively correlated with the mean flow velocity (v) and the mean turbulent kinetic energy (k) in the flow channel, and η tends to increase and then decrease with the increase of x. The retention time of the particles in the flow channel is closely related to the magnitude of v and k. Three multivariate lin ear regression equations (R2 = 0.883–0.995) were constructed for q0.1, x, and η versus the flow channel structural parameters. The optimal design combination of channel structure parameters for different scenarios was determined using the scipy.optimize.minimize function in Python 3.8.0. The research results provide a reference for the optimal design of variable flow emitters.

Macrotransport of active particles in periodic channels and fields: Rectification and dispersion.

Transport and dispersion of active particles in structured environments, such as corrugated channels and porous media, are important for the understanding of both natural and engineered active systems. Owing to their continuous self-propulsion, active particles exhibit rectified transport under spatially asymmetric confinement. While progress has been made in experiments and particle-based simulations, a theoretical understanding of the effective long-time transport dynamics in spatially periodic geometries remains less developed. In this paper, we apply generalized Taylor dispersion theory to analyze the long-time effective transport dynamics of active Brownian particles (ABPs) in periodic channels and fields. We show that the long-time transport behavior is governed by an effective advection-diffusion equation. The derived macrotransport equations allow us to characterize the average drift and effective dispersion coefficient. For the case of ABPs subject to a no-flux boundary condition at the channel wall, we show that regardless of activity, the average drift is given by the net diffusive flux along the channel. For ABPs, their activity is the driving mechanism that sustains a density gradient, which ultimately leads to rectified motion along the channel. Our continuum theory is validated against direct Brownian dynamics simulations of the Langevin equations governing the motion of each ABP.

VOF-DEM study of particle entrainment behaviors in the gas–solid-liquid system with multi-inlet configuration

Enhancing the entrainment capability of particles by bubbles is pivotal for facilitating particle elutriation and augmenting reaction efficiency in gas–liquid-solid systems. The current work utilizes the volume of fluid method in conjunction with discrete element method (VOF-DEM) to study particle entrainment in gas–liquid-solid three-phase reactors featuring different gas inlet layouts. Following model validation, this study delves into the multiphase flow characteristics and particle behaviors in detail. The results reveal that the merging of adjacent channels leads to the formation of larger combined bubbles, thereby increasing particle force, velocity and entrainment height. The average entrainment height during the merging of adjacent bubble channels is 42% higher compared to the four-channel configuration. However, this amalgamation diminishes the channel count and particle entrainment count. Specifically, the highest particle entrainment occurs in the two-channel configuration, which is 26% greater than that in the adjacent-channel merging configuration. Conversely, increasing the channel number decreases bubble size and overall particle entrainment capacity. With consistent bubble sizes, an increase in particle entrainment is associated with reduced entrainment height, indicative of diminished momentum transfer from bubble wakes to individual particles. Additionally, maintaining an optimal number of channels ensures high gas inlet velocity and bubble size, thereby enhancing particle entrainment efficiency. Lastly, appropriately reducing channel distance fosters interaction between adjacent channels, resulting in a meandering bubble path that further promotes particle entrainment and elution efficiency. The results obtained from this study serve as a useful reference for the design and optimization of similar systems.

Multicast-based fault-tolerant multiparty state preparation of four-qubit cluster states

The primary aim of this study is to utilize multicast in the preparation of multi-party four-qubit cluster states. In the presence of environment noises, errors may influence the procedure of the particle distribution. To address this challenge, we propose a fault-tolerant scheme to manage the errors within the detectable channel particles. Based on the Bell chain channel, our approach could prepare arbitrary four-particle cluster state by introducing auxiliary particles, where the receiver performs the unitary operation for recovering the target states. Compared to previous multicast protocols, our scheme reduces resource consumption and operational complexity during cluster state preparation. Additionally, we analyze the system’s fidelity in incoherent environments, providing a more comprehensive understanding of the impact of noise on quantum communication systems.

Generalized Langevin subdiffusion in channels: The bath always wins.

We consider subdiffusive motion, modeled by the generalized Langevin equationin an equilibrium setting, of tracer particles in channels of indefinite length in the x direction: the channels of varying width and the channels with sinusoidally meandering midline. The subdiffusion in the x direction is not affected by constraints put by the channel. This is especially astonishing for meandering channels whose centerline might be quite long. The same behavior is seen in a holonomic model of a bead on a sinusoidal and meandering wire, where some analytic insights are possible.

Robust Long-Nanowire Fabrication by Clean-Phase-Assisted Micro Chemical Pen for Enhanced Bioassay Sensitivity.

Long nanowires offer an increased surface area for biomolecule immobilization, facilitating enhanced binding capacity and sensitivity in the detection of target analytes. However, robust long-nanowire fabrication remains a significant challenge. In this paper, we developed a novel construction of a micro chemical pen (MCP), called a clean-assisted micro chemical pen (CAMCP), for robust long-nanowire fabrication. CAMCP, based on localized hydrodynamic flow confinement, was conducted by incorporating a clean phase to effectively dissolve aggregated silver particles in the aspiration channel's shell, thereby enhancing the MCP's longevity by 60.84%, allowing for an 840 μm extension in nanowire patterning capability. A 4600-aspect ratio (length:1200 μm, width: 260 nm) nanowire was fabricated by CAMCP and utilized as a nanowire sensor, showing a 39.7% increase in IgA detection sensitivity compared to a 3000-aspect ratio sensor. Furthermore, the longer nanowire sensor exhibited enhanced signal responses, a higher signal-to-noise ratio, and a lower limit of detection (LOD). The preponderant bioassay performances of the longer nanowire sensor in bioassays, facilitated by CAMCP, open up its possibilities for chemical-synthesis nanowires (NWs) in ultrasensitive biodetection.

Lattice Boltzmann simulation on particle suspensions containing porous particles in a narrow channel

The suspension of porous particles in fluids occurs widely in various natural and industrial processes. However, the sedimentation behavior of porous particles is not extensively understood as the solid impermeable counterparts. In this work, the drafting–kissing–tumbling (DKT) phenomenon in a narrow channel containing porous particles is investigated by the multi-relaxation-time (MRT) lattice Boltzmann method (LBM). The initial particle spacing Lp* (1.5∼6) and Darcy number Da (8×10−6∼6×10−2) are examined on the sedimentation process of two particles under three initial arrangements, i.e., the trailing particle is porous (case 1), the leading particle is porous (case 2), and both the particles are porous (case 3). The results show that the presence of porous particles can enhance the interactions between two particles, and increasing the penetrability reduces the particle drag force to accelerate sedimentation. The drafting time is insensitive to Da at small Lp*, and it decreases with Da at large Lp* in cases 1 and 3 while it changes to increase with Da in case 2. A phase diagram with respect to Da and Lp* is further extracted to identify three sedimentation modes of particle pairs. It is found that the transition between the one-off DKT and repeated DKT modes is not affected by Lp* in cases 2 and 3, while the critical condition for the non-DKT and one-off DKT modes depends strongly on Da and Lp* in case 2.

A High-Reliability Quantum Communication Protocol via Controllable-Signal Attenuation

Since the protocol for counterfactual quantum communication was proposed, complete counterfactuality can be achieved as there are no physical particles in the transmission channel. However, it relies on some restrictive factors, such as requiring an infinite number of beam splitters and no degradation. We conducted numerical simulations to assess the reliability of quantum communication combined with the actual test environment and found that the inevitable degradation, including component losses or path losses, limits the number of beam splitters. Furthermore, we carried out the experimental simulation of a high-reliability direct communication protocol using the method of controllable-signal attenuation. The peak reliability of μ1=27.6±0.22 that was obtained was much higher than the current communication protocol of the chained interferometer system. The optimized experimental equipment could compensate the system’s balance under various restrictive conditions and make it possible to achieve 100% reliability with imperfect interferometers.

The diffusion behaviour of coupled particle rings driven by self-propelled particles in a two-dimensional reflection channel

Investigated the diffusion behavior of self-propelled coupled particle rings in a two-dimensional channel considering particle collisions. The channel geometry and noise regulation play crucial roles in directing transport within the system. Observed a significant alteration in the diffusion behavior of the particle rings at specific stages of the collision process, accompanied by corresponding changes in the diffusion coefficient. As the modulation phase shift increases, the mean square displacement (MSD) of the particle rings displays periodic fluctuations. The binding force between the particle rings partially restricts the growth of the MSD. An increase in white noise intensity enhances the diffusion behavior. The impact of self-propulsion speed is influenced by the modulation parameters. The sign of the modulation parameter dictates the correlation of the self-propulsion speed. Furthermore, the number of particle rings in the channel introduces a complex effect on the diffusion behavior.

Crystal channeling investigations at medical synchrotron regimes

An experimental setup to investigate ion channeling in the hundreds MeV/u energy range is described. A short bent crystal, aligned to the incoming beam by an angular actuator, should deflect ions into a single plane pixel detector used to identify channeled and unchanneled particles. In order to enhance the footprint of channeling on the recorded signals, the incoming particle emittance is tailored on the crystalline plane acceptance by means of massive collimators. Numerical simulations of low energy carbon ions are performed with FLUKA to fully understand the measurement conditions demonstrate the feasibility of the test, to be performed in the experimental room of the National Center for Oncological Hadrontherapy accelerator complex in Pavia, Italy.

Characterizing Acoustic Behavior of Silicon Microchannels Separated by a Porous Wall.

Lateral flow membrane microdevices are widely used for chromatographic separation processes and diagnostics. The separation performance of microfluidic lateral membrane devices is determined by mass transfer limitations in the membrane, and in the liquid phase, mass transfer resistance is dependent on the channel dimensions and transport properties of the species separated by the membrane. We present a novel approach based on an active bulk acoustic wave (BAW) mixing method to enhance lateral transport in micromachined silicon devices. BAWs have been previously applied in channels for mixing and trapping cells and particles in single channels, but this is, to the best of our knowledge, the first instance of their application in membrane devices. Our findings demonstrate that optimal resonance is achieved with minimal influence of the pore configuration on the average lateral flow. This has practical implications for the design of microfluidic devices, as the channels connected through porous walls under the acoustic streaming act as 760 µm-wide channels rather than two 375 µm-wide channels in the context of matching the standing pressure wave criteria of the piezoelectric transducer. However, the roughness of the microchannel walls does seem to play a significant role in mixing. A roughened (black silicon) wall results in a threefold increase in average streaming flow in BAW mode, suggesting potential avenues for further optimization.

Elasto-inertial particle focusing in sinusoidal microfluidic channels.

Dean flow existing in sinusoidal channels could enhance the throughput and efficiency for elasto-inertial particle focusing. However, the fundamental mechanisms of elasto-inertial focusing in sinusoidal channels are still unclear. This work employs four microfluidic devices with symmetric and asymmetric sinusoidal channels to explore the elasto-inertial focusing mechanisms over a wide range of flow rates. The effects of rheological property, flow rate, sinusoidal channel curvature, particle size, and asymmetric geometry on particle focusing performance are investigated. It is intriguing to find that the Dean flow makes a substantial contribution to the particle elasto-inertial focusing. The results illustrate that a better particle focusing performance and a faster focusing process are obtained in the sinusoidal channel with a small curvature radius due to stronger Dean flow. In addition, the particle focusing performance is also related to particle diameter and rheological properties, the larger particles show a better focusing performance than smaller particles, and the smaller flow rate is required for particles to achieve stable focusing at the outlet in the higher concentration of polyvinylpyrrolidone solutions. Our work offers an increased knowledge of the mechanisms of elasto-inertial focusing in sinusoidal channels. Ultimately, these results provide supportive guidelines into the design and development of sinusoidal elasto-inertial microfluidic devices for high-performance focusing.

Experiment study on focusing pattern prediction of particles in asymmetric contraction-expansion array channel.

Contraction-expansion array (CEA) microchannel is a typical structure applied on particle/cell manipulation. The prediction of the particle focusing pattern in CEA microchannel is worthwhile to be investigate deeply. Here, we demonstrated a virtual boundary method by flow field analysis and theoretical derivation. The calculating method of the virtual boundary location, related to the Reynolds number (Re) and the structure parameter RW, was proposed. Combining the approximate Poiseuille flow pattern based on the virtual boundary method with the simulation results of Dean flow, the main line pattern and the main/lateral lines pattern were predicted and validated in experiments. The transformation from the main line pattern to the main/lateral lines pattern can be facilitated by increasing Re, decreasing RW , and decreasing α. An empirical formula was derived to characterize the critical condition of the transformation. The virtual boundary method can provide a guidance for asymmetric CEA channel design and contribute to the widespread application of microfluidic particle focusing.

Mass-Based Separation of Active Brownian Particles in an Asymmetric Channel

Inertial effects should be considered for micro and nanoswimmers moving in a low-density medium confined by irregular structures that create entropic barriers, where viscous effects are no longer paramount. Here, we present a separation mechanism of self-propelled particles in a two-dimensional asymmetric channel, which leads to the drift of particles of different masses in opposite directions. In particular, this mechanism is based on the combined action of the spatial asymmetry of the channel structure, the temporal asymmetry inherent in particles dynamics and an external static force. This work is relevant for potential applications that can be found in the development of lab-on-a-chip devices and artificial channels for separating particles of different masses.

Analysis of anti-clogging performance and particle transport characteristics of a stellate irrigation emitter

The service life and irrigation efficiency of drip irrigation systems are largely determined by the anti-clogging performance of the emitters. The degree and speed of clogging of the emitters are governed by the motion state of the particles in the flow channel. Computational fluid dynamics coupled discrete element method (CFD-DEM) and experiments were used to analyse anti-clogging performance and particles transport characteristics of a stellate irrigation emitter. With the angle of repose of sediment particles as the optimization objective, the key parameters of physical properties of sediment particles and container were obtained in the discrete phase model using a Plackett-Burman test, steepest climb test and Box-Behnken test. A novel evaluation method for assessing anti-clogging performance based on particles mass passing rate is proposed and its accuracy experimentally verified. Using three particles groups with different particle size distributions, the anti-clogging performance of stellate emitter was found to better than the widely used toothed emitter. In particular, the anti-clogging performance of the stellate emitter was found to be superior with the sensitive particle size of 0.03 mm. It was shown that sediment particles demonstrated retention, bonding and deposition in the inlet far away from the flow channel, the backwater area at the vertical vertex of the stellate structure and the backwater area at the joint of the stellate emitter flow channel structure units.

Research of the Wear Rate of Elements of the Flow Part of Centrifugal and Axial Pumping Units

The paper presents the results of a theoretical and experimental study of the wear rate of the elements of the flow part of centrifugal and axial pumps. Theoretical formulas recommended by various authors, obtained for models with flat samples based on energy theory, do not take into account the features of hydraulic machines. Considering the movement of solid particles in the inter-blade channels of the impellers of centrifugal and axial pumps, calculation schemes were chosen that correspond to the hydraulic and physical wear processes. The analysis shows that the influence of centrifugal and inertial forces in the inter-blade channel of the impellers of centrifugal and axial pumps causes separation and redistribution of solid particles in the flow. As a result, in centrifugal pumps in the end part of the blade and axial pumps in the end gap of the impeller, the local concentration of solid particles increases compared to the average. The work also provides dependencies for calculating the intensity of water-abrasive wear of pump working parts.

Analysis of the effect of flow channel structures on the centrifugal accelerated motion of particles in a vacuum state

In this study, the impact of flow channel structures on the acceleration of metal particles in a vacuum environment is explored, with the aim of enhancinge the acceleration quality in the centrifugal impact molding of metal powders. To assess this phenomenon, three evaluation indices are introduced: the average speed of particles thrown Vp\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${V}_{p}$$\\end{document}, the average speed of the particles Vall\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${V}_{all}$$\\end{document}, and the particle velocity distribution Vf (t). Additionally, the effects of six distinct runner structures on the centrifugal acceleration of the particles are analyzed in this research. The findings indicate that the arc-shaped flow channel structure not only ensures a more consistent acceleration process but also results in a higher ejection speed, leading to an improved acceleration effect. The unique contribution of this study is the examination of the relationship between flow channel designs and particle accelerations in a vacuum.

On the Generation of Phonons and Electronic Excitations by a Channeled Particle in Crystals

On the Generation of Phonons and Electronic Excitations by a Channeled Particle in Crystals

Fully resolved simulation of spherical and non-spherical particles in a turbulent channel flow

This paper investigates the behavior of finite-size particles in a turbulent channel flow using a custom direct numerical simulation solver within the FOAM-Extend framework. The solver integrates the cut-cell immersed boundary module with a Lagrangian particle-tracking subroutine capable of simulating the motion of both spherical and non-spherical particles. The study investigates the complex interactions between particles and turbulent structures, offering insights into how particle shape and orientation affect their behavior within the flow field. Additionally, it examines the collision dynamics of two spherical particles in a turbulent channel. The simulations reveal that particle shape significantly influences particle trajectories, rotation, and their interactions with turbulent structures. The Q-criterion visualization showed the creation of hairpin and vortex ring structures shed by the particles. Finally, the close proximity and collision of particles was shown to significantly modify the flow pattern and particle dynamics.