Particle Flow Research Articles

Programmable scanning diffuse speckle contrast imaging of cerebral blood flow.

Cerebral blood flow (CBF) imaging is crucial for diagnosing cerebrovascular diseases. However, existing large neuroimaging techniques with high cost, low sampling rate, and poor mobility make them unsuitable for continuous and longitudinal CBF monitoring at the bedside. We aimed to develop a low-cost, portable, programmable scanning diffuse speckle contrast imaging (PS-DSCI) technology for fast, high-density, and depth-sensitive imaging of CBF in rodents. The PS-DSCI employed a programmable digital micromirror device (DMD) for remote line-shaped laser (785nm) scanning on tissue surface and synchronized a 2D camera for capturing boundary diffuse laser speckle contrasts. New algorithms were developed to address deformations of line-shaped scanning, thus minimizing CBF reconstruction artifacts. The PS-DSCI was examined in head-simulating phantoms and adult mice. The PS-DSCI enables resolving intralipid particle flow contrasts at different tissue depths. In vivo experiments in adult mice demonstrated the capability of PS-DSCI to image global/regional CBF variations induced by 8% inhalation and transient carotid artery ligations. Compared with conventional point scanning, line scanning in PS-DSCI significantly increases spatiotemporal resolution. The high sampling rate of PS-DSCI is crucial for capturing rapid CBF changes while high spatial resolution is important for visualizing brain vasculature.

Remaining useful life prediction of lithium-ion batteries using a novel particle flow filter framework with grey model

Remaining useful life (RUL) prediction is a crucial aspect of the prognostics health management of lithium-ion batteries (LIBs). Owing to the influence of resampling technology, particle degradation is often observed in the particle filter-based RUL prediction of LIBs, resulting in a low prediction accuracy and large uncertainty. In this paper, a novel particle flow filter with the grey model method (GM-PFF) is proposed to forecast the RUL and state of health of batteries. First, the least squares method is employed to obtain the initial values for double exponential empirical model parameters. Subsequently, the grey model is used to predict the current cycle capacity of LIBs as an observation value for the particle flow filter, solving the inaccurate estimation problem of the state of particle flow filter observation values, and the particle flow filter method is employed to update model parameters. Finally, a test dataset is divided into early, middle, and late stages to predict the RUL of LIBs and obtain the probability distributions. On the CALCE and NASA PCoE LIB dataset, GM-PFF reduces RMSE by 1% compared to PFF, exhibiting a higher prediction accuracy and effectively addressing the particle degradation problem.

Measurements of decay branching fractions of the Higgs boson to hadronic final states at the CEPC

Abstract The Circular Electron Positron Collider (CEPC) is a large-scale particle accelerator designed to collide electrons and positrons at high energies. One of the primary goals of the CEPC is to achieve high-precision measurements of the properties of the Higgs boson, facilitated by the large number of Higgs bosons that can be produced with significantly low contamination. The measurements of Higgs boson branching fractions into bb/cc/gg and tautau/WW*/ZZ*, where the W or Z bosons decay hadronically, are presented in the context of the CEPC experiment, assuming a scenario with 5600 fb-1 of collision data at a center-of-mass energy of 240 GeV. In this study the Higgs bosons are produced in association with a Z boson, with the Z boson decaying into a pair of muons (μ+μ-), which have high efficiency and high resolution. In order to separate all decay channels simultaneously with high accuracy, the Particle Flow Network (PFN), a graph-based machine learning model, is considered. The precise classification provided by the PFN is employed in measuring the branching fractions using the migration matrix method, which accurately corrects for detector effects in each decay channel. The statistical uncertainty of the measured branching ratio is estimated to be 0.55% in H → bb final state, and approximately 1.5%-16% in H → cc/gg/tautau/WW*/ZZ* final states. In addition, the main sources of systematic uncertainties to the measurement of the branching fractions are discussed. Content from this work may be used under the terms of the Creative Commons Attribution 3.0 licence. Any further distribution of this work must maintain attribution to the author(s) and the title of the work, journal citation and DOI. Article funded by SCOAP3 and published under licence by Chinese Physical Society and the Institute of High Energy Physics of the Chinese Academy of Science and the Institute of Modern Physics of the Chinese Academy of Sciences and IOP Publishing Ltd.

A review of 3D particle tracking and flow diagnostics using Digital Holography

A review of 3D particle tracking and flow diagnostics using Digital Holography

Numerical Simulation Study on the Effect of Bend Angle on the Flow Characteristics of Natural Gas Hydrate Particles

ABSTRACTBend pipe is a commonly used part of long‐distance pipelines. It is very important to study the flow law of hydrate particles in the bend pipe to optimize pipeline design. In addition, the efficiency and safety of pipeline gas transmission will be improved. The flow of hydrate particles in the bend pipe is the research object of this paper, and the short twist tape is used as the spiral device, and numerical simulation methods are used to study the effects of the bend angle and the twist rate on the velocity distribution, turbulence intensity distribution, wall shear, particle movement and pressure drop distribution of the spiral flow carrying hydrate particles. The results show that as the twist rate of the twist tape is smaller, and the spiral flow is stronger, the fluid can generate a larger tangential velocity when flowing through the bend. The maximum speed at the section closest to the entrance is 28% higher than at the section furthest. Maximum tangential speed increased by 2 times. When the angle of the bend is larger, and velocity is more conducive to maintaining the spiral flow pattern of the particles, it is also more conducive to maintain. However, the twist rate is smaller, and the resistance is greater, then the pressure drop is greater, and the resistance coefficient of the bend pipe section is greater. With the increase of torsion, the pressure drop decreased by 52%. When the angle of the bend pipe section becomes smaller, it increases the collision frequency between the pipe wall and the natural gas. Unit pressure drop loss increased by 13%. When the angle is smaller, the change in the direction of the velocity of the particles will be more violent, and the pressure drop is larger, and the drag coefficient is larger. In the same section, the maximum turbulence intensity is about twice the minimum.

Effect of artificial viscosity on shocked particle-laden flows for staggered grid Lagrangian methods

Effect of artificial viscosity on shocked particle-laden flows for staggered grid Lagrangian methods

Visualization Experiment on the Influence of the Lost Circulation Material Injection Method on Fracture Plugging

The drilling fluid loss or lost circulation via near-wellbore fractures is one of the most critical problems in the drilling of deep oil and gas resources, which causes other problems such as difficulty in achieving wellbore pressure control and reservoir damage. The conventional treatment is to introduce granular lost circulation material (LCM) into the drilling fluid to plug the fractures. As the migration mechanism of the LCM in irregular fractures has not been completely figured out as of yet, the low success rate of fracture plugging and repeated drilling fluid loss still obstruct the exploitation of deep oil and gas resources. In this paper, the spatial data of actual rock fracture surfaces were obtained through structured light scanning, and an irregular surface identical to the rock was machined on a transparent polymethyl methacrylate plate. On this basis, a visualization experimental apparatus for fracture plugging was established, and the fracture flow space of this device was consistent with that of the actual rock fracture. Employing cylindrical nylon particles as LCM, a visualization experiment study was carried out to investigate the process of LCM bridging and fracture plugging and the influence of LCM injection methods. The experimental results show that the process of fracture plugging includes the sporadic bridging, plugging zone extension and merging, thickening of the plugging zone and complete plugging of the fracture. It was observed in the visualization experiment that a large number of small particles flow deep into the fracture in the traditional fracture plugging method, where all types and sizes of LCM are injected at one time. After changing the injection sequence, which injects the large particles first and the small particles subsequently, it is found that the large particles will form single-particle bridging at a specific depth of the fracture, intercepting subsequently injected particles and thickening the plugging zone, which finally increases the area of the plugging zone by 19%. The visualization experiment results demonstrate that modifying the LCM injection method significantly enhances both the LCM utilization rate and the fracture plugging effect, thereby reducing reservoir damage. This is conducive to reducing the drilling cost of fractured formation. Additionally, the visualized experimental approach introduced in this study can also benefit other research areas, including proppant placement and solute transport in rock fractures.

Numerical simulation of fracture evolution behaviors in deep roadway surrounding rock containing discontinuous joints

To explore the internal bearing characteristics and fracture evolution laws of discontinuous jointed rock mass in deep roadways, the −600 m main roadway in Xin ’an Coal Mine was used as the research background. The fracture fractal dimension D was employed to characterize the joint density, and an intermittent jointed roadway model, both without support and with anchor cable support, was modeled using the particle flow software PFC2D. The internal stress, deformation, and fracture characteristics of intermittent jointed surrounding rock in tunnels with different support methods and joint densities were studied from a microscopic perspective. The results indicate that during the bearing process of the bolt anchor support and unsupported roadway discontinuous jointed rock mass model, the main bearing area of both models transferred from the surface rock mass to the deep rock mass. The tensile cracks of the anchor cable support model were reduced by 57.7% compared with the unsupported model, effectively suppressed the tensile failure of the surrounding rock, and the convergence of the surrounding rock was substantially reduced. The density of intermittent joints was negatively correlated with the bearing capacity of the surrounding rock mass of roadways, and the increase of joint density the overall failure of the surrounding rock, and the possibility of roadway destabilization was increased. Importantly, the number and distribution of intermittent joints in the surface surrounding rock were closely related to the rupture characteristics of the roadways. When the load exceeded the ultimate load of the deep surrounding rock, stress fluctuation occurred due to the stress drop caused by its destruction. This fluctuation promoted the development of intermittent joints in the surface surrounding rock, increasing the risk of roadway destabilization.

Bearing characteristics and damage rules of regenerated rock mass

This study investigates the bearing characteristics and damage evolution of regenerative rock masses formed under varying geological conditions through uniaxial loading tests, numerical simulations, and theoretical derivations. Regenerative rock mass samples with different water-cement ratios and cementing materials were prepared, and the mechanical behavior during the loading process was analyzed. The results indicate that the secondary damage process can be divided into three stages: pre-peak, weakening, and friction. As the mechanical properties of the cementing matrix improve, the bearing capacity increases, and the failure mode transitions from ductile to brittle. A damage constitutive model incorporating the Weibull distribution and a damage correction coefficient is proposed to predict the mechanical strength of regenerative rock masses. Numerical simulations using Particle Flow Code 3D (PFC3D) reveal that enhanced mechanical properties of the cementing material lead to a shift from tensile to shear failure. This study provides theoretical and practical guidance for the stability control of regenerative rock mass engineering, offering new insights into the design of support systems for mining operations. The findings have significant implications for the recovery of shallow residual coal resources and the stability control of mining roadways.

Liquid flows induced in a rotating drum with different fill ratios

In the present study, we experimentally investigate the liquid flow induced in a rotating drum (cylindrical tank with a short aspect ratio) aligned horizontally, focusing on the variation in the time-averaged and fluctuating flow structures with different fill ratios. For each fill ratio, controlled by varying the water height, we measure the velocity fields at different cross-sectional planes with particle image velocimetry while varying the rotational speed of the drum. Compared to the condition of a fill ratio of 1.0, in which the liquid inside the drum rotates forming a large-scale (solid-body rotation) organized flow structure, a substantial asymmetric flow structure shows up in partially-filled conditions driven by the imbalance between (i) the momentum diffusion along the radial direction and the centrifugal acceleration, and (ii) the downward (gravitational) flux of the induced flow. In addition to the mean flow structure, we examine the fluctuating velocity fields together with the dynamics of the free surface, and we also briefly discuss the difference between the liquid flow and granular (particle) flow in a partially-filled drum. We think that the present results provide valuable insights on the partially-filled liquid drum toward various engineering applications.

Study on the Adhesion Properties of Raw Coal and Adhesive Clogging Characteristics of Underground Coal Bunkers

The automation and continuous operation of coal production are fundamental to the construction of high-yielding and efficient mines. Underground coal bunkers, serving as the pivotal link between various production and transportation segments, are vital for the seamless operation of mines. Nonetheless, the adhesive properties of raw coal can lead to increasingly severe issues, such as the adhesive clogging of coal bunkers. To address this issue, this paper first employs a self-designed raw coal shear testing apparatus to conduct experiments under varying conditions of shear interfaces, moisture content in raw coal, and compaction forces. Obtaining the adhesion behavior characteristics and adhesion parameter variation patterns of raw coal at coal-coal and coal-wall interfaces under various influencing factors. Subsequently, leveraging the adhesion property parameters of raw coal and the engineering conditions of the 1011 roadway coal bunker in Taoyuan Coal Mine II, a numerical model for coal bunker discharge using irregular particles was developed with the PFC2D numerical simulation software. Based on these, we obtained the influence patterns of various factors, such as coal bunker convergence angle, coal storage height, and coal moisture content, on the coal particle flow pattern, bunker wall pressure, and adhesive clogging distribution characteristics of the coal bunker during the discharge process, thereby revealing the mechanisms underlying the adhesive clogging phenomenon. The findings offer significant insights for optimizing solutions to the adhesive clogging issues in underground coal bunkers and ensuring their safe and efficient operation.

Damage Evolution and Failure Precursor of Rock-like Material Under Uniaxial Compression Based on Strain Rate Field Statistics

In rock engineering, it is crucial to collect and analyze precursor information of rock failure. This paper has attempted to study the strain rate field of rock-like material to obtain the precursor information of its failure. Based on the available laboratory experiments, the intact BPM (bonded-particle model) and other BPMs with a single open prefabricated flaw were simulated by PFC (Particle Flow Code). The volume strain rate field data before the peak stress have been obtained from two hundred measurement circles across each model. The strain rate field data have been firstly statistically analyzed to explore the failure precursor based on the intact model and 45° flaw model and then compared to find the influence of the pre-existing flaw on the damage evolution and precursor signal. The results indicate that (1) all types of statistical data are positively correlated with the increment of microcracks; (2) corresponding to the fluctuation patterns of statistical data, the damage evolution of BPMs in the pre-peak stage can be divided into three parts; (3) the pre-existing flaw would accelerate the damage evolution; (4) the location and evolution rate of damage could be determined by comprehensively analyzing the average deviation curve, the coefficient of variation, and the contour maps of the strain rate field. These analyses of the particle displacement field can be used to distinguish the impacts of the flaw angle and provide some assistance for the failure forecast.

Fabrication of enteric coated mucoadhesive pellets of Tofacitinib citrate for treatment of ulcerative colitis

Fabrication of enteric coated mucoadhesive pellets of Tofacitinib citrate for treatment of ulcerative colitis

Efficiency and scalability of fully-resolved fluid-particle simulations on heterogeneous CPU-GPU architectures

Current supercomputers often have a heterogeneous architecture using both conventional Central Processing Units (CPUs) and Graphics Processing Units (GPUs). At the same time, numerical simulation tasks frequently involve multiphysics scenarios whose components run on different hardware due to multiple reasons, e.g., architectural requirements, pragmatism, etc. This leads naturally to a software design where different simulation modules are mapped to different subsystems of the heterogeneous architecture. We present a detailed performance analysis for such a hybrid four-way coupled simulation of a fully resolved particle-laden flow. The Eulerian representation of the flow utilizes GPUs, while the Lagrangian model for the particles runs on conventional CPUs. Two characteristic model situations involving dense and dilute particle systems are used as benchmark scenarios. First, a roofline model is employed to predict the node level performance and to show that the lattice-Boltzmann-based Eulerian fluid simulation reaches very good performance on a single GPU. Furthermore, the GPU-GPU communication for a large-scale Eulerian flow simulation results in only moderate slowdowns. This is due to the efficiency of the CUDA-aware MPI communication, combined with the use of communication hiding techniques. On 1024 A100 GPUs, an overall parallel efficiency of up to 71% is achieved. While the flow simulation has good performance characteristics, the integration of the stiff Lagrangian particle system requires frequent CPU-CPU communications that can become a bottleneck, especially when simulating the dense particle system. Additionally, special attention is paid to the CPU-GPU communication overhead since this is essential for coupling the particles to the flow simulation. However, thanks to our problem-aware co-partitioning, the CPU-GPU communication overhead is found to be negligible. As a lesson learned from this development, four criteria are postulated that a hybrid implementation must meet for the efficient use of heterogeneous supercomputers.

Creep model of bond-degradation in deep granite based on variable radius particle clump

The creep failure of rocks is related to its microstructure, external loading and time. A nonlinear yield model was introduced to describe the variation in the cohesion and friction angle with plastic strain and intergranular stress. The mechanical properties and creep characteristics of deep granite were obtained by indoor tests, and a variable radius particle clump model was constructed based on the particle flow method. The bond-weakening-friction-strengthening model was combined with the parallel bond stress corrosion method to establish the bond-degradation creep model of granite. The creep failure time, creep rate and tension and shear fractures number of the parallel bond stress corrosion model and the bond-degradation creep model were compared and analyzed to verify the applicability of the model. The fracture evolution law of deep roadway surrounding rock was studied based on the bond-degradation creep model. The results show that the rock failure characteristics and tension-compression ratio obtained by the variable radius particle clump modeling method are closer to the actual situation. Compared with the parallel bond stress corrosion model, the creep failure time of the bond-degradation creep model is shorter, more microfractures are generated during the failure process, and the numerical creep curves are more consistent with the test curves. The deep roadway vault shear failure and sidewall plate crack failure characteristics calculated based on the bond-degradation creep model are basically similar to the actual project situation. The bond-degradation creep model can better simulate the creep damage process of rocks under high stress, and is more suitable for analyzing the fracture evolution law of surrounding rock in deep hard rock cavern.

Liquid metal electrodes enabled cascaded on-chip dielectrophoretic separation of large-size-range particles.

The separation of large-size-range particles of complex biological samples is critical but yet well resolved. As a label-free technique, dielectrophoresis (DEP)-based particle separation faces the challenge of how to configure DEP in an integrated microfluidic device to bring particles of various sizes into the effective DEP force field. Herein, we propose a concept that combines the passive flow fraction mechanism with the accumulative DEP deflection effect in a cascaded manner. This concept places DEP deflection segments and bypass outlets alternately. Each DEP deflection segment is configured with an array of side-wall liquid metal electrodes to exert effective DEP forces on the particles of a suitable size range. After each DEP deflection segment, the passive bypass flow fraction mechanism diverts part of the sample flow and target range of particles through the bypass outlet. Simultaneously, this flow fraction brings the remaining particles closer to the electrodes in the subsequent DEP deflection segment, causing the next size range of particles to deflect under effective DEP forces and thus making them separable. Repeating this process, particles would be separated from the bypass outlets one by one in the order of reducing size ranges. We present the concept design and modeling, and prove the concept through separating five different particles ranging from 16-0.5 μm mixed together to mimic blood composition, providing a powerful platform for separating multiple particles in diverse biomedical applications.

Coupling of non-hydrostatic model with unresolved point-particle model for simulating particle-laden free surface flows

Coupling of non-hydrostatic model with unresolved point-particle model for simulating particle-laden free surface flows

Wastewater-induced microplastic biofouling in freshwater: role of particle size and flow velocity

Wastewater-induced microplastic biofouling in freshwater: role of particle size and flow velocity

Investigation of drafting-kissing-tumbling movement of two particles with conjugate heat transfer

The conjugate heat transfer at the particle-fluid interface and the collision between particles play a crucial role in the sedimentation process of particles. In this work, the recent volumetric lattice Boltzmann method for thermal particulate flows with conjugate heat transfer is adopted to investigate the drafting-kissing-tumbling movement in the sedimentation process of two particles in a closed channel. This volumetric lattice Boltzmann method is based on double distribution functions, with the density distribution function used for the velocity field and the internal energy distribution function used for the temperature field. It is a single-domain approach, and the nonslip velocity condition within the solid domain can be strictly ensured. The difference in thermophysical properties between the solid and fluid can be correctly handled, and the conjugate heat transfer condition can be automatically achieved without any additional treatments. Based on this particle-resolved simulation, the influences of the solid-to-fluid specific heat ratio, the Grashof number, and the particle’s initial temperature on the drafting-kissing-tumbling movement are discussed in detail. It is found that the fluid cooled by the particle and thus subjected to the downward buoyancy force can promote particle sedimentation. As the specific heat ratio increases, the particle’s temperature rises relatively slowly. In the sedimentation of two cold particles, the drafting duration and tumbling duration of the drafting-kissing-tumbling movement decrease when the heat capacity ratio increases. In contrast, the kissing duration increases as the heat capacity ratio increases. When the Grashof number increases, the heat transfer between the particle and fluid is enhanced, and the drafting duration significantly decreases while the kissing duration and tumbling duration remain almost unchanged in the sedimentation of two cold particles. The particle’s initial temperature greatly affects the occurrence moment of the drafting-kissing-tumbling movement. To be specific, the drafting-kissing-tumbling movement occurs at the earliest moment for the sedimentation of two cold particles, followed by the sedimentation of one cold and one hot particle, and the latest for the sedimentation of two hot particles. The promoting effect of the low particle’s initial temperature on the drafting-kissing-tumbling movement mainly takes place in the dragging stage and kissing stage. The particle’s initial temperature has almost no influence on the tumbling duration.

Ensemble Kalman, adaptive Gaussian mixture, and particle flow filters for optimized earthquake occurrence estimation

Ensemble Kalman, adaptive Gaussian mixture, and particle flow filters for optimized earthquake occurrence estimation