Journal articles on the topic 'Particle'
To see the other types of publications on this topic, follow the link: Particle.
Create a spot-on reference in APA, MLA, Chicago, Harvard, and other styles
Consult the top 50 journal articles for your research on the topic 'Particle.'
Next to every source in the list of references, there is an 'Add to bibliography' button. Press on it, and we will generate automatically the bibliographic reference to the chosen work in the citation style you need: APA, MLA, Harvard, Chicago, Vancouver, etc.
You can also download the full text of the academic publication as pdf and read online its abstract whenever available in the metadata.
Browse journal articles on a wide variety of disciplines and organise your bibliography correctly.
1
Baktybekov, K. "PARTICLE SWARM OPTIMIZATION WITH INDIVIDUALLY BIASED PARTICLES FOR RELIABLE AND ROBUST MAXIMUM POWER POINT TRACKING UNDER PARTIAL SHADING CONDITIONS." Eurasian Physical Technical Journal 17, no. 2 (December 24, 2020): 128–37. http://dx.doi.org/10.31489/2020no2/128-137.
Full textAbstract:
Efficient power control techniques are an integral part of photovoltaic system design. One of the means of managing power delivery is regulating the duty cycle of the DC to DC converter by various algorithms to operate only at points where power is maximum power point. Search has to be done as fast as possible to minimize power loss, especially under dynamically changing irradiance. The challenge of the task is the nonlinear behavior of the PV system under partial shading conditions. Depending on the size and structure of the photovoltaic panels, PSC creates an immense amount of possible P-V curves with numerous local maximums - requiring an intelligent algorithm for determining the optimal operating point. Existing benchmark maximum power point tracking algorithms cannot handle multiple peaks, and in this paper, we offer an adaptation of particle swarm optimization for the specific task.
2
Kan, Hiroyuki, Hideya Nakamura, and Satoru Watano. "Effect of particle wettability on particle-particle adhesion of colliding particles through droplet." Powder Technology 302 (November 2016): 406–13. http://dx.doi.org/10.1016/j.powtec.2016.08.066.
Full text
3
Lin, J. H., and K. C. Chang. "Particle Dispersion Simulation in Turbulent Flow Due to Particle-Particle and Particle-Wall Collisions." Journal of Mechanics 32, no. 2 (August 19, 2015): 237–44. http://dx.doi.org/10.1017/jmech.2015.63.
Full textAbstract:
AbstractSimulation of the 3-D, fully developed turbulent channel flows laden with various mass loading ratios of particles is made using an Eulerian-Lagrangian approach in which the carrier-fluid flow field is solved with a low-Reynolds-number k-ε turbulence model while the deterministic Lagrangian method together with binary-collision hard-sphere model is applied for the solution of particle motion. Effects of inter-particle collisions and particle-wall collisions under different extents of wall roughness on particle dispersion are addressed in the study. A cost-effective searching algorithm of collision pair among particles is developed. It is found that the effects of inter-particle collisions on particle dispersion cannot be negligible when the ratio of the mean free time of particle to the mean particle relaxation time of particle is less or equal to O(10). In addition, the wall roughness extent plays an important role in the simulation of particle-wall collisions particularly for cases with small mass loading ratios.
4
Orozco, Luisa Fernanda, Jean-Yves Delenne, Philippe Sornay, and Farhang Radjai. "Effect of particle shape on particle breakage inside rotating cylinders." EPJ Web of Conferences 249 (2021): 07002. http://dx.doi.org/10.1051/epjconf/202124907002.
Full textAbstract:
We study the influence of particle shape on the evolution of particle breakage process taking place inside rotating cylinders. Extensive particle dynamics simulations taking into account the dynamics of the granular flow, particle breakage, and polygonal particle shapes were carried out. We find that the rate of particle breakage is faster in samples composed of initially rounder particles. The analysis of the active flowing layer thickness suggests that for samples composed of rounder particles a relatively lower dilatancy and higher connectivity lead to a less curved free surface profile. As a result, rounder particles rolling down the free surface have a higher mobility and thus higher velocities. In consequence, the faster breakage observed for rounder initial particles is due to the larger particles kinetic energy at the toe of the flow.
5
Wu, Z., W. Birmili, L. Poulain, M. Merkel, B. Fahlbusch, D. van Pinxteren, H. Herrmann, and A. Wiedensohler. "Particle hygroscopicity during atmospheric new particle formation events: implications for the chemical species contributing to particle growth." Atmospheric Chemistry and Physics Discussions 12, no. 5 (May 3, 2012): 11415–43. http://dx.doi.org/10.5194/acpd-12-11415-2012.
Full textAbstract:
Abstract. This study examines the hygroscopicity of newly formed particles (smaller than 50 nm in particle mobility diameter) during two atmospheric new particle formation events with and without clear growth process at mid-level mountain range in Central Germany based on HCCT field campaign. Particle hygroscopicity measurements show that the particle soluble fractions at the end of event for two events are, respectively 60% (45 nm particles for the event with clear growth) and 20% (30 nm particles for the event without clear growth), stressing that non-soluble organic compounds may play a key role in particle growth during new particle formation event. Such significant difference in particle hygroscopicity also suggests that the chemical species responsible for nucleation particle growth are considerably different between the two selected NPF events. During both events, the hygroscopicity of newly formed particles decreased with particle growth, indicating that more less-hygroscopic compounds contribute to the subsequent condensation in contrast to the earlier stage. Sulfuric acid was considered to be responsible of the NPF event and represent the highly hygroscopic compounds. However, calculation demonstrated that sulfuric acid condensation failed to fully explain the observed soluble fraction in the nucleation mode particles. Therefore, we hypothesize that some water-soluble matters may explain the missing soluble fraction.
6
Delvosalle, C., and J. Vanderschuren. "Gas-to-particle and particle-to-particle heat transfer in fluidized beds of large particles." Chemical Engineering Science 40, no. 5 (1985): 769–79. http://dx.doi.org/10.1016/0009-2509(85)85030-2.
Full text
7
von Gladiss, Anselm, Matthias Graeser, Kerstin Lüdtke-Buzug, and Thorsten M. Buzug. "Contribution of brownian rotation and particle assembly polarisation to the particle response in magnetic particle spectrometry." Current Directions in Biomedical Engineering 1, no. 1 (September 1, 2015): 298–301. http://dx.doi.org/10.1515/cdbme-2015-0074.
Full textAbstract:
AbstractThe spectrometry of super-paramagnetic iron-oxide nanoparticles is a central tool for characterising particles that are used in Magnetic Particle Imaging. In Magnetic Particle Imaging, nanoparticles are excited by a magnetic field and the particle response is measured. Until now, the influence of the trajectory sequence on the dynamic particle relaxation has not been scoped. With a multi-dimensional Magnetic Particle Spectrometer, analysing the behaviour of different trajectories on the particles becomes possible. In this paper, the contribution of Brownian rotation and assembly polarisation on the particle signal is being analysed.
8
Schiepel, D., S. Herzog, R. Barta, and C. Wagner. "A Probabilistic Particle Tracking Framework For High Particle Densities." Proceedings of the International Symposium on the Application of Laser and Imaging Techniques to Fluid Mechanics 20 (July 11, 2022): 1–10. http://dx.doi.org/10.55037/lxlaser.20th.43.
Full textAbstract:
A framework for particle tracking velocimetry at high particle densities (HD-PTV) based on a Gaussian Mixture Model (GMM) is presented. This new approach is validated by tracking synthetic particles generated for a generalized turbulent pipe flow defining the ground truth. For a step size per time step of δS = 14 px and a particles per pixel (ppp) density of 0.09 the framework tracks about 90% of the ground truth particles (percentage of matched particles, pmp) already after 9 time steps without generating any ghost particles. For a lower step size of δS = 7 px, corresponding to a higher temporal resolution of the flow, and the lowest investigated particle density ppp = 0.02 a constant pmp close to 100% is reported. A decrease on pmp to 80% is found for the highest ppp = 0,11 - corresponding to about 45000 particles in total. Increasing the step size per time step to δS = 14 px results in a similar sloping curve and pmp that are generally 5% lower compared to the lower step size. The approach is further successfully applied to a well-known experimental tracking problem, i.e. particle tracking in turbulent Rayleigh-Bénard convection, for which the motion of about 28500 particles is tracked. With track lengths up to 250 times steps the occuring structures and velocities are investigated and agree well with previous studies based on tomographic particle image velocimetry using the same data. Thus, it is concluded that the presented HD-PTV framework is an appropriate tool for the flow analysis even at high particle densities.
9
Kim, S., S. H. Cho, and H. Park. "Effects of particle size distribution on the cake formation in crossflow microfiltration." Water Supply 2, no. 2 (April 1, 2002): 305–11. http://dx.doi.org/10.2166/ws.2002.0077.
Full textAbstract:
In crossflow microfiltration, the tendency of particle deposition of polydisperse suspensions has been established experimentally and compared with that of monodisperse suspensions. The mass transfers of particles are different according to size in polydisperse suspensions. The most particles, which deposit to membrane surface without clogging pore in microfiltration, are much larger than 0.1 μm. Among these particles, smaller particles are easier to deposit than larger particles because of shear-induced diffusion and particle deposition depends on the size distribution of small particles. Effective particle diameter is introduced as a representative particle size which can reflect the diffusivity of each particle according to size and it describes the tendency of particle deposition very well in polydisperse suspensions. The effect of effective particle diameter is larger than that of feed concentration. The most important factor affecting particle deposition of polydisperse suspensions is effective particle diameter. The results of our research suggest that the effective particle diameter can be an important factor which can represent the potential for cake formation.
10
Qing, Yun, Zhenfeng Qiu, Yi Tang, Wenjie Deng, Xujin Zhang, Jilun Miu, and Shaoxian Song. "Effects of the Particle Shape and Size on the Single-Particle Breakage Strength." Advances in Civil Engineering 2022 (December 1, 2022): 1–10. http://dx.doi.org/10.1155/2022/3386025.
Full textAbstract:
The strength and deformation of a soil foundation are related to the strength of each particle. Maybe the shape affects the strength of a particle. In this study, single-particle breakage tests were conducted on limestone particles of different sizes to analyze the influence of limestone particle shapes on the particle crushing strength. The results showed that 90 percent of limestone particle shapes were oblate spherical, subspherical, and long spherical particles randomly selected from the soil foundation. The single-particle breakage test results showed that the characteristic stress of limestone particles increases with the increased particle size. The crushing strength of limestone particles increased with the increase in particle size. There was a significant size effect on the single-particle compressive strength. The relationship between the characteristic strength and the particle size can be fitted by a power exponential formulation of four types of limestone particle shapes. The more irregular the particle shape, the smaller the Weibull modulus (m) and the power index and the more obvious the particle strength size effect.
11
Yi-Fang, Chang. "Final Simplest Model of Smallest Particles and Possibly Developed Directions of Particle Physics." Physical Science & Biophysics Journal 5, no. 2 (2021): 1–12. http://dx.doi.org/10.23880/psbj-16000196.
Full textAbstract:
First, so far the high energy experiments in the past sixty years have shown that the smallest mass fermions are proton, electron, neutrino and photon, which form the simplest model of particles. These fermions seem to be inseparable truth “atoms” (elements), because further experiments derive particles with bigger mass. They correspond to four interactions, and are also only stable particles. Next, the final simplest theory is based on leptons (e- e ν ) and nucleons (p-n) or (u-d) in quark model with SU(2) symmetry and corresponding Yang-Mills field. Other particles and quark-lepton are their excited states. Their spectrum is mass formula and symmetric lifetime formula. Some applications are discussed. Further, the simplest interactions and unification of weak-strong interactions by QCD are discussed. We research opposite continuous separable models. Finally, we propose some possibly developed directions of particle physics, for example, violation of basic principles, in particular, the uncertainty principle, and precision and systematization of the simplest model, etc.
12
Hou, Yu Bao, and Shu Yan Tang. "Breeding Estimated Particle Filter." Advanced Materials Research 740 (August 2013): 332–37. http://dx.doi.org/10.4028/www.scientific.net/amr.740.332.
Full textAbstract:
As the normal particle filter has an expensive computation and degeneracy problem, a propagation-prediction particle filter is proposed. In this scheme, particles after transfer are propagated under the distribution of state noise, and then the produced filial particles are used to predict the corresponding parent particle referring to measurement, in which step the newest measure information is added into estimation. Therefore predicted particle would be closer to the true state, which improves the precision of particle filter. Experiment results have proved the efficiency of the algorithm and the great predominance in little particles case.
13
Hirosawa, Fumie, Tomohiro Iwasaki, and Masashi Iwata. "Particle Impact Energy Variation with the Size and Number of Particles in a Planetary Ball Mill." MATEC Web of Conferences 333 (2021): 02016. http://dx.doi.org/10.1051/matecconf/202133302016.
Full textAbstract:
To investigate the mechanical energy applying to the particles in a grinding process using a planetary ball mill, the impact energy of particles was estimated by simulating the behavior of the particles and grinding balls using the discrete element method (DEM) under different conditions of the size and number of particles, corresponding to their variations during milling. As the impact energy contributing to the particle breakage, we focused on the particle impact energy generated at particle-to-grinding ball/wall and particle-to-particle collisions. The particle size and the number of particles affected the level of particle impact energy at a single collision and the number of collisions of particles, respectively, resulting in an increase of the total impact energy of particles with decreasing particle size and increasing number of particles. The result suggests that milling conditions such as the size of grinding balls should be adjusted appropriately based on the variation of the size and number of particles so that the particles can receive large amounts of the impact energy during milling.
14
Hirosawa, Fumie, Tomohiro Iwasaki, and Masashi Iwata. "Particle Impact Energy Variation with the Size and Number of Particles in a Planetary Ball Mill." MATEC Web of Conferences 333 (2021): 02016. http://dx.doi.org/10.1051/matecconf/202133302016.
Full textAbstract:
To investigate the mechanical energy applying to the particles in a grinding process using a planetary ball mill, the impact energy of particles was estimated by simulating the behavior of the particles and grinding balls using the discrete element method (DEM) under different conditions of the size and number of particles, corresponding to their variations during milling. As the impact energy contributing to the particle breakage, we focused on the particle impact energy generated at particle-to-grinding ball/wall and particle-to-particle collisions. The particle size and the number of particles affected the level of particle impact energy at a single collision and the number of collisions of particles, respectively, resulting in an increase of the total impact energy of particles with decreasing particle size and increasing number of particles. The result suggests that milling conditions such as the size of grinding balls should be adjusted appropriately based on the variation of the size and number of particles so that the particles can receive large amounts of the impact energy during milling.
15
KAWASAKI, Yousuke, Haruzou MIYASITA, and Tosio KIKUCHI. "Particles. Particle Measurements in Vacuum by In Situ Particle Monitor Sensor." SHINKU 41, no. 9 (1998): 771–75. http://dx.doi.org/10.3131/jvsj.41.771.
Full text
16
Gonon, P., J. N. Foulc, P. Atten, and C. Boissy. "Particle–particle interactions in electrorheological fluids based on surface conducting particles." Journal of Applied Physics 86, no. 12 (December 15, 1999): 7160–69. http://dx.doi.org/10.1063/1.371807.
Full text
17
Ichiji, M., H. Akiba, H. Nagao, and I. Hirasawa. "Particle size distribution control of Pt particles used for particle gun." Journal of Crystal Growth 469 (July 2017): 180–83. http://dx.doi.org/10.1016/j.jcrysgro.2016.09.003.
Full text
18
Yang, Yang, and Hongguang Zhu. "Development of Particle-fluid Drag Model for Individual Wheat Straw Particle." Journal of Physics: Conference Series 2287, no. 1 (June 1, 2022): 012044. http://dx.doi.org/10.1088/1742-6596/2287/1/012044.
Full textAbstract:
Abstract To deal with the sedimentation of wheat straw particles in the process of conveying and mixing, the drag model of the non-spherical particle is to be developed. In this work the settling velocity of sheared and the defibered particles are acquired by image analysis. The simulating settling velocity of particle is acquired by ANSYS Fluent. As a result, the KG-based drag models with shape factors of Π, AR, BR, and Φ are obtained respectively by fitting the relation between drag coefficient and particle Reynold for 24 sheared particles. The settling velocity of 24 particles are acquired by simulation. In addition, the six drag models are used to simulate settling velocity of 134 defibered particles. At last, the means value of relative error of velocity between the shear and the defibered particles are acquired, they are 20%, 23%, 19%, 59%, respectively, corresponding to the shape factors of Π, AR, BR and Ψ. Considering the pValue of curve fitting, the drag model with shape factor Π is best for simulating the wheat straw particles in particle-liquid flow.
19
Guo, Y., C. Wassgren, W. Ketterhagen, B. Hancock, B. James, and J. Curtis. "A numerical study of granular shear flows of rod-like particles using the discrete element method." Journal of Fluid Mechanics 713 (October 12, 2012): 1–26. http://dx.doi.org/10.1017/jfm.2012.423.
Full textAbstract:
AbstractThe effect of particle aspect ratio and surface geometry on granular flows is assessed by performing numerical simulations of rod-like particles in simple shear flows using the discrete element method (DEM). The effect of particle surface geometry is explored by adopting two types of particles: glued-spheres particles and true cylindrical particles. The particle aspect ratio varies from one to six. Compared to frictionless spherical particles, smaller stresses are obtained for the glued-spheres and cylindrical particle systems in dilute and moderately dense flows due to the loss of translational energy, which is partially converted to rotational energy, for the non-spherical particles. For dilute granular flows of non-spherical particles, stresses are primarily affected by the particle aspect ratio rather than the surface geometry. As the particle aspect ratio increases, the effective particle projected area in the plane perpendicular to the flow direction increases, so that the probability of the occurrence of the particle collisions increases, leading to a reduction in particle velocity fluctuation and therefore a decrease in the stresses. Hence, a simple modification is made to the kinetic theory for granular flows to describe the stress tensors for dilute flows of non-spherical particles by incorporating a normalized effective particle projected area to account for the effect of particle collision probability. For dense granular flows, the stresses depend on both the particle aspect ratio and the surface geometry. Sharp stress increases at high solid volume fractions are observed for the glued-spheres particles with large aspect ratios due to the bumpy surfaces, which impede the flow. However, smaller stresses are obtained for the true cylindrical particles with large aspect ratios at high solid volume fractions. This trend is attributed to the combined effects of the smooth particle surfaces and the particle alignments such that the major/long axes of particles are aligned in the flow direction. In addition, the apparent friction coefficient, defined as the ratio of shear to normal stresses, is found to decrease as the particle aspect ratio increases and/or the particle surface becomes smoother at high solid volume fractions.
20
Yao, Hai Tao, Hai Qiang Chen, and Tuan Fa Qin. "Niche PSO Particle Filter with Particles Fusion for Target Tracking." Applied Mechanics and Materials 239-240 (December 2012): 1368–72. http://dx.doi.org/10.4028/www.scientific.net/amm.239-240.1368.
Full textAbstract:
An improved particle filter algorithm is proposed to track a randomly moving target in video. In particle filter framework, a particle swarm optimization improved by niche technique which implemented by restricted competition selection is integrated. It can move particles into high likelihood area of target and form multi-population distribution, so that the searching capability of particles is enhanced and then the adaptation to the change of dynamic target state is improved. The particles of niching particle swarm optimization and the particles of particle filter are integrated for new particle weight calculation and finally realize a new particle filter for target tracking in video sequence.
21
Nakada, Nobuo, Masahiro Murakami, Toshihiro Tsuchiyama, and Setsuo Takaki. "Work Hardening Mechanism in Soft Particle Dispersion Ferritic Steel." Materials Science Forum 706-709 (January 2012): 2199–204. http://dx.doi.org/10.4028/www.scientific.net/msf.706-709.2199.
Full textAbstract:
The work hardening behavior was investigated in ferritic steels containing hard particles or soft Cu particles with various volume fractions and particle diameters, and then the effect of plastically deformable soft particles on the work hardening was evaluated in terms of the accumulation of GN dislocations. The amount of work hardening and dislocation density increased with an increase of volume fraction of dispersion particles and a decrease of particle diameter in hard particle dispersion steel. On the other hand, in soft Cu particle dispersion steel, the effect of volume fraction and particle diameter on work hardening behavior was relatively small. TEM observation suggested that stress relaxation around particle takes place by plastic deformation of Cu particle itself. In order to consider the effect of plastic deformation of Cu particles on accumulation of GN dislocations, "particle plastic accommodation parameter" was proposed to modify the Ashby's work hardening theory. As a result, the amount of work hardening was successfully predicted for both the hard and soft particle dispersion steels
22
Xue, Rui, and Hou Qian Xu. "Investigation of Particle Flow Field in Pyrotechnic Flame Based on Particle Image and Particle Velocity." Advanced Materials Research 962-965 (June 2014): 2789–96. http://dx.doi.org/10.4028/www.scientific.net/amr.962-965.2789.
Full textAbstract:
Study on burning particles in flame can help us to grasp the pyrotechnic decomposition mechanism. The high speed video (HSV) and particle image velocity (PIV) were used in this paper to analyze the flow field consist of high temperature burning particles during pyrotechnic combustion. The binary image was obtained through grayscale treatment and adaptive threshold segmentation from HSV and PIV data, by which the coordinate of each particle was marked. On the basis, the movement trajectory of each particle during combustion was pursued by the most recent guidelines algorithm of cancroids matching. Through the method proposed in this study, the velocity variation of each particle was obtained, the approximate distribution of particle quantity at each zone was visualized and the mathematical model of pyrotechnic particle velocity flow field was established.
23
Kwon, Soon Chul, Tadaharu Adachi, Wakako Araki, and Akihiko Yamaji. "Effect of Particle Size on Fracture Toughness of Spherical-Silica Particle Filled Epoxy Composites." Key Engineering Materials 297-300 (November 2005): 207–12. http://dx.doi.org/10.4028/www.scientific.net/kem.297-300.207.
Full textAbstract:
We investigated the particle size effects on the fracture toughness of epoxy resin composites reinforced with spherical-silica particles. The silica particles had different mean particle diameters of between 1.56 and 0.24µm and were filled with bisphenol A-type epoxy resin under different mixture ratios of small and large particles and a constant volume fraction for all particles of 0.30. As the content with the added smaller particle increased, the viscosity of each composite before curing remarkably increased. We conducted the single edge notched bending test (SENB) to measure the mode I fracture toughness of each composite. The fracture surface with the small particle content exhibited more rough areas than the surface with larger particles. The fracture toughness increased below the small particle content of 0.8 and saturated above it. Therefore, near the small particle content of 0.8, the composite had a relatively low viscosity and a high fracture toughness.
24
Schmidt, Susan, Johannes Schneider, Thomas Klimach, Stephan Mertes, Ludwig Paul Schenk, Piotr Kupiszewski, Joachim Curtius, and Stephan Borrmann. "Online single particle analysis of ice particle residuals from mountain-top mixed-phase clouds using laboratory derived particle type assignment." Atmospheric Chemistry and Physics 17, no. 1 (January 12, 2017): 575–94. http://dx.doi.org/10.5194/acp-17-575-2017.
Full textAbstract:
Abstract. In situ single particle analysis of ice particle residuals (IPRs) and out-of-cloud aerosol particles was conducted by means of laser ablation mass spectrometry during the intensive INUIT-JFJ/CLACE campaign at the high alpine research station Jungfraujoch (3580 m a.s.l.) in January–February 2013. During the 4-week campaign more than 70 000 out-of-cloud aerosol particles and 595 IPRs were analyzed covering a particle size diameter range from 100 nm to 3 µm. The IPRs were sampled during 273 h while the station was covered by mixed-phase clouds at ambient temperatures between −27 and −6 °C. The identification of particle types is based on laboratory studies of different types of biological, mineral and anthropogenic aerosol particles. The outcome of these laboratory studies was characteristic marker peaks for each investigated particle type. These marker peaks were applied to the field data. In the sampled IPRs we identified a larger number fraction of primary aerosol particles, like soil dust (13 ± 5 %) and minerals (11 ± 5 %), in comparison to out-of-cloud aerosol particles (2.4 ± 0.4 and 0.4 ± 0.1 %, respectively). Additionally, anthropogenic aerosol particles, such as particles from industrial emissions and lead-containing particles, were found to be more abundant in the IPRs than in the out-of-cloud aerosol. In the out-of-cloud aerosol we identified a large fraction of aged particles (31 ± 5 %), including organic material and secondary inorganics, whereas this particle type was much less abundant (2.7 ± 1.3 %) in the IPRs. In a selected subset of the data where a direct comparison between out-of-cloud aerosol particles and IPRs in air masses with similar origin was possible, a pronounced enhancement of biological particles was found in the IPRs.
25
Li, Xiaohui, Guodong Liu, Junnan Zhao, Xiaolong Yin, and Huilin Lu. "IBM-LBM-DEM Study of Two-Particle Sedimentation: Drafting-Kissing-Tumbling and Effects of Particle Reynolds Number and Initial Positions of Particles." Energies 15, no. 9 (April 30, 2022): 3297. http://dx.doi.org/10.3390/en15093297.
Full textAbstract:
Particle sedimentation is a fundamental process encountered in various industrial applications. In this study, we used immersed boundary lattice Boltzmann method and discrete element method (IBM-LBM-DEM) to investigate two-particle sedimentation. A lattice Boltzmann method was used to simulate fluid flow, a discrete element method was used to simulate particle dynamics, and an immersed boundary method was used to handle particle–fluid interactions. Via the IBM-LBM-DEM, the particles collision process in fluid or between rigid walls can be calculated to capture the information of particles and the flow field more efficiently and accurately. The numerical method was verified by simulating settling of a single three-dimensional particle. Then, the effects of Reynolds number (Re), initial distance, and initial angle of particles on two-particle sedimentation were characterized. A specific focus was to reproduce, analyze, and define the well-known phenomenon of drafting-kissing-tumbling (DKT) interaction between two particles. Further kinematic analysis to define DKT is meaningful for two-particle sedimentation studies at different particle locations. Whether a pair of particles has experienced DKT can be viewed from time plots of the distance between the particles (for kissing), the second-order derivative of distance to time (for drafting), and angular velocities of particles (for tumbling). Simulation results show that DKT’s signatures, including attraction, (near) contact, rotation, and in the end, separation, is only completely demonstrated when particles have nearly vertically aligned initial positions. Hence, not all initial positions of particles and Reynolds numbers lead to DKT and not all particle–particle hydrodynamic interactions are DKT. Whether particle–particle interaction is attractive or repulsive depends on the relative positions of particles and Re. Collision occurs when Re is high and the initial angle is small (<20°), almost independent of the initial distance.
26
Kontkanen, Jenni, Chenjuan Deng, Yueyun Fu, Lubna Dada, Ying Zhou, Jing Cai, Kaspar R. Daellenbach, et al. "Size-resolved particle number emissions in Beijing determined from measured particle size distributions." Atmospheric Chemistry and Physics 20, no. 19 (October 5, 2020): 11329–48. http://dx.doi.org/10.5194/acp-20-11329-2020.
Full textAbstract:
Abstract. The climate and air quality effects of aerosol particles depend on the number and size of the particles. In urban environments, a large fraction of aerosol particles originates from anthropogenic emissions. To evaluate the effects of different pollution sources on air quality, knowledge of size distributions of particle number emissions is needed. Here we introduce a novel method for determining size-resolved particle number emissions, based on measured particle size distributions. We apply our method to data measured in Beijing, China, to determine the number size distribution of emitted particles in a diameter range from 2 to 1000 nm. The observed particle number emissions are dominated by emissions of particles smaller than 30 nm. Our results suggest that traffic is the major source of particle number emissions with the highest emissions observed for particles around 10 nm during rush hours. At sizes below 6 nm, clustering of atmospheric vapors contributes to calculated emissions. The comparison between our calculated emissions and those estimated with an integrated assessment model GAINS (Greenhouse Gas and Air Pollution Interactions and Synergies) shows that our method yields clearly higher particle emissions at sizes below 60 nm, but at sizes above that the two methods agree well. Overall, our method is proven to be a useful tool for gaining new knowledge of the size distributions of particle number emissions in urban environments and for validating emission inventories and models. In the future, the method will be developed by modeling the transport of particles from different sources to obtain more accurate estimates of particle number emissions.
27
Zhang, Kaituo, and Zhiyong Lv. "Quantitative Measuring Analysis Method and Mechanism of Wear Particle Settlement." E3S Web of Conferences 252 (2021): 03037. http://dx.doi.org/10.1051/e3sconf/202125203037.
Full textAbstract:
The size and distribution of wear particle in lubricating oil, as important numerical information available in ferrography, is one of the key indexes in wear diagnosis. In this paper, a new method for measuring the size and distribution of abrasive particles is proposed. First, all the abrasive fluid is left standing until all the abrasive particles are precipitated to the bottom. Then, the measuring container is inverted and the whole precipitation process of abrasive particles is recorded by magnetic induction instrument. And according to the precipitation analysis of the wear particle, the following results were obtained:1) At the initial stage of the particle settlement, the gravity, the buoyancy and the drag force of the oil achieve balance quickly, the time and distance of the wear particle moving at a constant velocity can be neglected. 2) The settling velocity is related to the diameter and specific gravity of the wear particle as well as the specific gravity and viscosity of the oil, the distribution of the wear particle is proportional to the square of the diameter of the particle, using the magnetic induction technology, the distribution of particle can be measured by settling time for different sizes of wear particles. 3) Measure the wear particle oil directly, there are different sizes of particles settlement in the bottom at the same time, which causes the difficulty in identifying the size of the particle settlement. The particle should be settled first, and then inverted, settling the particle in accordance with the order from large to small, which facilitates the measurement of different sizes of the particles, different times correspond to different sizes of the particles. 4) The bigger the particle is, the more accurate the measurement and counting is, the smaller the particle is, the bigger the error is.
28
Kim, J. K., and D. F. Lawler. "Particle detachment during hydraulic shock loads in granular media filtration." Water Science and Technology 53, no. 7 (March 1, 2006): 177–84. http://dx.doi.org/10.2166/wst.2006.222.
Full textAbstract:
Particle breakthrough can occur by either the breakoff of previously captured particles (or flocs) or the direct passage of some influent particles through the filter. Filtration experiments were performed in a laboratory-scale filter using spherical glass beads with a diameter of 0.55 mm as collectors. A single type of particle suspension (Min-U-Sil 5) and three different destabilisation methods (pH control, alum and polymer destabilisation) were used to destabilise particles. The filtration velocity of 5 m/h was similar to that used in standard media filtration practice. To assess the possibility of particle detachment during normal filtration, a hydraulic shock load (20% increase of flow rate) was applied after 4 h of normal filtration. The magnitude of particle detachment was proportional to the particle size for non-Brownian particles. At the same time, less favourable particles, i.e. particles with larger surface charge, were easily detached during the hydraulic shock load. Therefore, proper particle destabilisation before filtration is crucial for maximum particle removal, as well as minimum particle breakthrough.
29
Dolanský, Jindřich, Zdeněk Chára, Pavel Vlasák, and Bohuš Kysela. "Lattice Boltzmann method used to simulate particle motion in a conduit." Journal of Hydrology and Hydromechanics 65, no. 2 (June 1, 2017): 105–13. http://dx.doi.org/10.1515/johh-2017-0008.
Full textAbstract:
AbstractA three-dimensional numerical simulation of particle motion in a pipe with a rough bed is presented. The simulation based on the Lattice Boltzmann Method (LBM) employs the hybrid diffuse bounce-back approach to model moving boundaries. The bed of the pipe is formed by stationary spherical particles of the same size as the moving particles. Particle movements are induced by gravitational and hydrodynamic forces. To evaluate the hydrodynamic forces, the Momentum Exchange Algorithm is used. The LBM unified computational frame makes it possible to simulate both the particle motion and the fluid flow and to study mutual interactions of the carrier liquid flow and particles and the particle–bed and particle–particle collisions. The trajectories of simulated and experimental particles are compared. The Particle Tracking method is used to track particle motion. The correctness of the applied approach is assessed.
30
CHAN, TSAN UNG. "WHAT IS A MATTER PARTICLE?" International Journal of Modern Physics E 15, no. 01 (February 2006): 259–72. http://dx.doi.org/10.1142/s0218301306003916.
Full textAbstract:
Positive baryon numbers (A>0) and positive lepton numbers (L>0) characterize matter particles while negative baryon numbers and negative lepton numbers characterize antimatter particles. Matter particles and antimatter particles belong to two distinct classes of particles. Matter neutral particles are particles characterized by both zero baryon number and zero lepton number. This third class of particles includes mesons formed by a quark and an antiquark pair (a pair of matter particle and antimatter particle) and bosons which are messengers of known interactions (photons for electromagnetism, W and Z bosons for the weak interaction, gluons for the strong interaction). The antiparticle of a matter particle belongs to the class of antimatter particles, the antiparticle of an antimatter particle belongs to the class of matter particles. The antiparticle of a matter neutral particle belongs to the same class of matter neutral particles. A truly neutral particle is a particle identical with its antiparticle; it belongs necessarily to the class of matter neutral particles. All known interactions of the Standard Model conserve baryon number and lepton number; matter cannot be created or destroyed via a reaction governed by these interactions. Conservation of baryon and lepton number parallels conservation of atoms in chemistry; the number of atoms of a particular species in the reactants must equal the number of those atoms in the products. These laws of conservation valid for interaction involving matter particles are indeed valid for any particles (matter particles characterized by positive numbers, antimatter particles characterized by negative numbers, and matter neutral particles characterized by zero). Interactions within the framework of the Standard Model which conserve both matter and charge at the microscopic level cannot explain the observed asymmetry of our Universe. The strong interaction was introduced to explain the stability of nuclei: there must exist a powerful force to compensate the electromagnetic force which tends to cause protons to fly apart. The weak interaction with laws of conservation different from electromagnetism and the strong interaction was postulated to explain beta decay. Our observed material and neutral universe would signify the existence of another interaction that did conserve charge but did not conserve matter.
31
Moreno-Casas, Patricio A., Juan Pablo Toro, Sebastián Sepúlveda, José Antonio Abell, Eduardo González, and Joongcheol Paik. "The Effect of Particle Concentration on Bed Particle Diffusion in Dilute Flows." Water 14, no. 19 (October 2, 2022): 3105. http://dx.doi.org/10.3390/w14193105.
Full textAbstract:
In this paper, we present the simulation results of a Lagrangian particle tracking model that computes the motion of saltating sediment particles, which is considered the most important mode of bedload transport in rivers and channels. The model is one-way coupled to a validated turbulent LES-WALE (Large Eddy Simulation – Wall-Adapting Local Eddy-viscosity) channel flow, i.e., the particles do not affect the computation of the flow velocities and pressures, as suggested for dilute flows. The model addresses the particle trajectories, the collision of the particles with the bottom wall, and collision among particles. The focus of this work is placed on the effect of different particle concentrations and flow intensities (different flow shear stresses) on jump statistics and particle diffusion. Numerical results are validated with experimental laboratory data obtained from the literature for particle diameters in the range of sands. The present results indicate that, at particle concentrations up to 2%, the diffusion coefficients in the streamwise and spanwise directions, γx and γz, for the local range are nearly constants with a value close to one, corresponding to the ballistic regime. At a concentration of 4%, the largest concentration studied herein, values of γx and γz for the local range are slightly smaller, with a representative value of 0.9 regardless of flow intensities. For the intermediate regime, it was found that, on average, γx~1.2γz with γx ranging from 0.6 to 0.85 and γz within the range 0.45–0.70. For a fixed flow intensity, both diffusion coefficients increase with the particle concentration, which is an indication of the contribution of the collision among particles to particle diffusion. For highly controlled simulation conditions, the differences in particle velocity at a given concentration may change drastically, which should translate to important fluctuations in the computation of sediment transport rates. Finally, the employed computational resources are described as a function of particle concentration. Although the number of total collisions increases linearly with the number of particles, the number of collisions per particle reaches a plateau, thus indicating that there exists an upper limiting value for the number of collisions per particle.
32
Williams, Sarah G. W., and David J. Furbish. "Particle energy partitioning and transverse diffusion during rarefied travel on an experimental hillslope." Earth Surface Dynamics 9, no. 4 (July 14, 2021): 701–21. http://dx.doi.org/10.5194/esurf-9-701-2021.
Full textAbstract:
Abstract. Rarefied particle motions on rough hillslope surfaces are controlled by the balance between gravitational heating of particles due to conversion of potential to kinetic energy and frictional cooling of the particles due to collisions with the surface. Here we elaborate on how particle energy is partitioned between kinetic, rotational, and frictional forms during downslope travel using measurements of particle travel distances on a laboratory-scale hillslope, supplemented with high-speed imaging of drop–impact–rebound experiments. The drop–impact–rebound experiments indicate that particle shape has a dominant role in energy conversion during impact with a surface. Relative to spherical and natural rounded particles, angular particles give greater variability in rebound behavior, resulting in more effective conversion of translational to rotational energy. The effects of particle shape on energy conversion are especially pronounced on a sloping sand-roughened surface. Angular particles travel shorter distances downslope than rounded particles, though travel distance data for both groups are well fit by generalized Pareto distributions. Moreover, particle–surface collisions during downslope motion lead to a transverse random-walk behavior and transverse particle diffusion. Transverse spreading increases with surface slope as there is more available energy to be partitioned into the downslope or transverse directions during collision due to increased gravitational heating. Rounded particles exhibit greater transverse diffusion than angular particles, as less energy is lost during collision with the surface. Because the experimental surface is relatively smooth, this random-walk behavior represents a top-down control on the randomization of particle trajectories due to particle shape, which is in contrast to a bottom-up control on randomization of particle trajectories associated with motions over rough surfaces. Importantly, transverse particle diffusion during downslope motion may contribute to a cross-slope particle flux and likely contributes to topographic smoothing of irregular hillslope surfaces such as scree slopes.
33
Jackson, Dane N., and Barton L. Smith. "Theoretical Parameter Study of Aerodynamic Vectoring Particle Sorting." Journal of Fluids Engineering 129, no. 7 (January 10, 2007): 902–7. http://dx.doi.org/10.1115/1.2742732.
Full textAbstract:
A new particle sorting technique called aerodynamic vectoring particle sorting (AVPS) has recently been shown to be effective at sorting particles without particles contacting surfaces. The technique relies on turning a free jet sharply without extended control surfaces. The flow turning results in a balance of particle inertia and several forces (pressure, drag, added mass, and body forces) that depend on particle size and density. The present paper describes a theoretical study of particle sorting in a turning flow. The purpose of this study is to extend AVPS to parameter spaces other than those that are currently under investigation. Spherical particles are introduced into a turning flow in which the velocity magnitude increases like r. The trajectory of each particle is calculated using the particle equation of motion with drag laws that are appropriate for various Knudsen number regimes. Large data sets can be collected rapidly for various particle sizes, densities, turning radii, flow speeds, and fluid properties. Ranges of particle sizes that can be sorted are determined by finding an upper bound (where particles move in a straight line) and a lower bound (where particles follow flow streamlines). It is found that the size range of particles that can be sorted is larger for smaller turning radii, and that the range moves toward smaller particles as the flow speed and the particle-to-fluid density ratio are increased. Since this flow is laminar and 2-D, and particle loading effects are ignored, the results represent a “best case” scenario.
34
Schneiders, Lennart, Konstantin Fröhlich, Matthias Meinke, and Wolfgang Schröder. "The decay of isotropic turbulence carrying non-spherical finite-size particles." Journal of Fluid Mechanics 875 (July 22, 2019): 520–42. http://dx.doi.org/10.1017/jfm.2019.516.
Full textAbstract:
Direct particle–fluid simulations of heavy spheres and ellipsoids interacting with decaying isotropic turbulence are conducted. This is the rigorous extension of the spherical particle analysis in Schneiders et al. (J. Fluid Mech., vol. 819, 2017, pp. 188–227) to $O(10^{4})$ non-spherical particles. To the best of the authors’ knowledge, this represents the first particle-resolved study on turbulence modulation by non-spherical particles of near-Kolmogorov-scale size. The modulation of the turbulent flow is precisely captured by explicitly resolving the stresses acting on the fluid–particle interfaces. The decay rates of the fluid and particle kinetic energy are found to increase with the particle aspect ratio. This is due to the particle-induced dissipation rate and the direct transfer of kinetic energy, both of which can be substantially larger than for spherical particles depending on the particle orientation. The extra dissipation rate resulting from the translational and rotational particle motion is quantified to detail the impact of the particles on the fluid kinetic energy budget and the influence of the particle shape. It is demonstrated that the previously derived analytical model for the particle-induced dissipation rate of smaller particles is valid for the present cases albeit these involve significant finite-size effects. This generic expression allows us to assess the impact of individual inertial particles on the local energy balance independent of the particle shape and to quantify the share of the rotational particle motion in the kinetic energy budget. To enable the examination of this mechanistic model in particle-resolved simulations, a method is proposed to reconstruct the so-called undisturbed fluid velocity and fluid rotation rate close to a particle. The accuracy and robustness of the scheme are corroborated via a parameter study. The subsequent discussion emphasizes the necessity to account for the orientation-dependent drag and torque in Lagrangian point-particle models, including corrections for finite particle Reynolds numbers, to reproduce the local and global energy balance of the multiphase system.
35
Xu, Mindi, and Hwa-Chi Wang. "Minimum Sampling Time/Volume for Liquid-Borne Particle Counters and Monitors." Journal of the IEST 40, no. 6 (November 1, 1997): 29–34. http://dx.doi.org/10.17764/jiet.2.40.6.uh6153l0661882v5.
Full textAbstract:
A particle counter is an instrument that measures particles in all the fluid passing through its sensor, and a particle monitor measures particles only in a portion of the fluid. For liquid with an ultralow particle concentration, particles may not disperse uniformly in the liquid. Therefore, the concentrations may vary significantly from measurement to measurement if the sample volume is not large enough. To achieve the same precision, a minimum sampling time or minimum sample volume for a particle instrument needs to be specified. A Poisson distribution was used to describe the distribution of particle counts. Testing included a series of particle concentration measurements. Minimum sampling time or sample volume at a given average concentration with different error levels was determined for selected commercial particle instruments. At the same flow rate, a particle monitor always requires a longer sampling time than a particle counter to achieve a specific precision for a given concentration. The minimum sampling time also varies among instruments because of the difference in sample volume in which the particles are counted. Experiments with a particle monitor have been conducted to thest the changes in average particle concentration and the standard deviation at different operating conditions.
36
AL-DEAIBES, MUTASIM. "The Morpho-Syntax of Clausal Negation in Rural Jordanian Arabic." JOURNAL OF ADVANCES IN LINGUISTICS 5, no. 3 (March 7, 2015): 750–60. http://dx.doi.org/10.24297/jal.v5i3.2860.
Full textAbstract:
In this paper, I argue that the Neg particles head their projections, and the negation in a hierarchical representation occurs between TP and VP. In future tense, I argue that the Aux can move to the Neg head just to pick the negation and then the negative particle and the Aux moves to T. I also show that speakers of RJA use different negation constructions depending on the structure and tense of the sentence. For example, the negative particle ma is a preverbal particle used with present and past verbs evenly. The negative particle ma¦-ƒ is a pre and post-verbal particle where ma is a proclitic and -ƒ is an enclitic. This particle is used with present verbs and past verbs. However, when used with present tense verbs, the proclitic ma becomes optional, whereas with past tense verbs the deletion of the proclitic ma results in an ungrammatical sentence. As for copular sentences, the particle miƒ is used to negate verbless copular sentences where there is a covert present tense verb. But, when the copular sentence is formed via a past tense verb, miƒ is no longer used. Instead, the negative construction maâ¦-ƒ is used.
37
Liu, Liming, Mengqin Zhan, Rongtao Wang, and Yefei Liu. "Three-Dimensional VOF-DEM Simulation Study of Particle Fluidization Induced by Bubbling Flow." Processes 12, no. 6 (May 21, 2024): 1053. http://dx.doi.org/10.3390/pr12061053.
Full textAbstract:
The bubbling flow plays a key role in gas–liquid–solid fluidized beds. To understand the intrinsic fluidization behaviors at the discrete bubble and particle scale, coupled simulations with the volume of fluid model and the discrete element method are performed to investigate the effects of the gas inlet velocity, particle properties and two-orifice bubbling flow on particle fluidization. Three-dimensional simulations are carried out to accurately capture the dynamic changes in the bubble shape and trajectory. A bubbling flow with a closely packed bed is simulated to study the onset of particle fluidization. The obvious phenomena of particle fluidization are presented by both the experiment and simulation. Although an increasing gas inlet velocity promotes particle fluidization, the good fluidization of particles cannot be achieved solely by increasing the gas inlet velocity. When the channel is packed with more particles, the bubbles take a longer time to pass through the higher particle bed, and the bubbles grow larger in the bed. The increase in particle density also extends the time needed for the bubbles to escape from the bed, and it is more difficult to fluidize the particles with a larger density. Even if more particles are added into the channel, the percentage of suspended particles is not significantly changed. The percentage of suspended particles is not increased with a decrease in the particle diameter. The particle suspension is not significantly improved by the bubbling flow with two orifices, while the particle velocity is increased due to the more frequent bubble–particle collisions. The findings from this study will be beneficial in guiding the enhancement of particle fluidization in multiphase reactors.
38
Schanz, D., T. Jahn, and A. Schröder. "3D Particle Position Determination And Correction At High Particle Densities." Proceedings of the International Symposium on the Application of Laser and Imaging Techniques to Fluid Mechanics 20 (July 11, 2022): 1–17. http://dx.doi.org/10.55037/lxlaser.20th.214.
Full textAbstract:
The method of Iterative Particle Reconstruction (IPR), introduced by Wieneke in 2013, constitutes a major step towards high-density 3D Lagrangian Particle Tracking. It reconstructs 3D particle positions from their projections onto several cameras. In the first part of this work, we present several approaches to enhance the original IPR working principle which, in combination, nearly triple the processable particle image densities, allowing complete and ghost-free reconstructions on a single snapshot from a four-camera system at up to 0.14 particles-per pixel (ppp). The updated method is proven to be fast, accurate and robust against image noise and other imaging artifacts. A central piece of the IPR functionality is a position optimization algorithm, using the difference of the local re-projected and original images (the residual images) as a cost function and displacing particles along its steepest gradient ('shaking' of the particles). The same approach is used within the Shake-The-Box (STB) Lagrangian Particle Tracking (LPT) scheme to correct predicted particle positions. The positional errors to be corrected during IPR-processing are typically in the sub-pixel range, however larger errors can occur at the prediction stage of STB. The second part of this manuscript quantifies the ability of the position optimization to successfully correct misplaced particles and proposes a method to further increase this range. Cost-function-gradient based methods require a certain overlap of the re-projected image with the original image for any given particle. Still, a misplacement of 2-3 pixels - depending on its direction relative to the camera positions - is shown to be reliably correctable. As seen by statistics from a DNS of a turbulent cylinder flow, such high accelerations (and therefore mispredictions) are rare at typical sampling rates. Therefore, most particle predictions can be successfully optimized to the correct position. In order to additionally handle rare events of large acceleration and misplacement, an iterative grid-search is applied specifically to particles not being optimally placed yet ('Variable Space step', VS). Such particles are identified using the local shape of the cost-function gradient. Using synthetic data, it is demonstrated that this method is able to correct even large prediction errors with high reliability. Applying a low temporal sampling on the test case of turbulent cylinder flow results in 20.8 px average particle shift. In this case, using noisy image data at a particle image density of 0.1 ppp, approx. 95.3% of the particle predictions can be corrected by pure position optimization, while around 99.5 % are achieved by additionally applying VS. Transferring this approach to experimental data could further improve tracking fidelity and would allow relaxing on the temporal resolution demands.
39
Ju, Hongling, Fanquan Bian, and Mingrui Wei. "Modeling of soot particle collision and growth paths in gas-solid two-phase flow." Thermal Science, no. 00 (2020): 215. http://dx.doi.org/10.2298/tsci191110215j.
Full textAbstract:
Particle collision is an important process in soot particle growth. In this research, based on gas-solid two-phase flow, particle trajectory was traced by the Lagrange approach with periodic boundaries. Trajectory intersection, collision probability, and critical velocity were considered, and the growth path of each particle was traced. The collision frequency (fc), agglomeration frequency (fa), and friction collision frequency (ffc) were calculated, and the main influence factors of particle collision were analyzed. The results showed that fc, fa, fa/fcincreased with the increase of the particle volume fraction and gasphasevelocity(v), but the particle initial diameter (dpi) andvhad the great influence on fa/fc. fa/fcobviously decreased with the increase of dpiand v.The statistical analysis of fa/fcand Stokes number showed that fa/fcdecreased with the increase of Stokes number, especially when stokes number was extremely small, fa/fcdecreased rapidly. Using the trajectory analysis of each particle, the particle growth process could be classified in three types: firstly, the particles that did not agglomerate with any particles during the entire calculation process; secondly, the particles that continually agglomerated with small particles to generate larger ones; and finally, the particles that were agglomerated by larger particles at some calculation moment.
40
Alireza Ghasemi, S., Alexey Neelov, and Stefan Goedecker. "A particle-particle, particle-density algorithm for the calculation of electrostatic interactions of particles with slablike geometry." Journal of Chemical Physics 127, no. 22 (December 14, 2007): 224102. http://dx.doi.org/10.1063/1.2804382.
Full text
41
Dodds, David, Abd Alhamid R. Sarhan, and Jamal Naser. "CFD Investigation into the Effects of Surrounding Particle Location on the Drag Coefficient." Fluids 7, no. 10 (October 17, 2022): 331. http://dx.doi.org/10.3390/fluids7100331.
Full textAbstract:
In the simulation of dilute gas-solid flows such as those seen in many industrial applications, the Lagrangian Particle Tracking method is used to track packets of individual particles through a converged fluid field. In the tracking of these particles, the most dominant forces acting upon the particles are those of gravity and drag. In order to accurately predict particle motion, the determination of the aforementioned forces become of the upmost importance, and hence an improved drag force formula was developed to incorporate the effects of particle concentration and particle Reynolds number. The present CFD study examines the individual effects of particles located both perpendicular and parallel to the flow direction, as well as the effect of a particle entrain within an infinite matrix of evenly distributed particles. Results show that neighbouring particles perpendicular to the flow (Model 2) have an effect of increasing the drag force at close separation distances, but this becomes negligible between 5–10 particle diameters depending on particle Reynolds number (Rep). When entrained in an infinite line of particles co-aligned with the flow (Model 1), the drag force is remarkably reduced at close separation distances and increases as the distance increases. The results of the infinite matrix of particles (Model 3) show that, although not apparent in the individual model, the effect of side particles is experienced many particle diameters downstream.
42
Yao, Xin, Chyi Huey Ng, Jia Rui Amanda Teo, Marcos, and Teck Neng Wong. "Slow viscous flow of two porous spherical particles translating along the axis of a cylinder." Journal of Fluid Mechanics 861 (December 28, 2018): 643–78. http://dx.doi.org/10.1017/jfm.2018.918.
Full textAbstract:
We describe the motion of two freely moving porous spherical particles located along the axis of a cylindrical tube with background Poiseuille flow at low Reynolds number. The stream function and a framework based on cylindrical harmonics are adopted to solve the flow field around the particles and the flow within the tube, respectively. The two solutions are employed in an iterated framework using the method of reflections. We first consider the case of two identical particles, followed by two particles with different dimensions. In both cases, the drag force coefficients of the particles are solved as functions of the separation distance between the particles and the permeability of the particles. The detailed flow field in the vicinity of the two particles is investigated by plotting the streamlines and velocity contours. We find that the particle–particle interaction is dependent on the separation distance, particle sizes and permeability of the particles. Our analysis reveals that when the permeability of the particles is large, the streamlines are more parallel and the particle–particle interaction has less effect on the particle motion. We further show that a smaller permeability and bigger particle size generally tend to squeeze the streamlines and velocity contour towards the wall.
43
Zhang, L. M., Y. Xu, R. Q. Huang, and D. S. Chang. "Particle flow and segregation in a giant landslide event triggered by the 2008 Wenchuan earthquake, Sichuan, China." Natural Hazards and Earth System Sciences 11, no. 4 (April 26, 2011): 1153–62. http://dx.doi.org/10.5194/nhess-11-1153-2011.
Full textAbstract:
Abstract. During the 12 May 2008 Wenchuan earthquake, a large landslide of approximately 30 million m3 occurred at Donghekou with a particle run-out distance of over 2000 m. This paper presents fascinating particle flow and segregation characteristics in the landslide process found through field investigation of changes in the soil particle size, density, and fabric along the particle movement paths. The soil particles experienced projection, long-distance flying, sliding, and rolling. Trajectory segregation, inverse grading, and particle crushing were found in the landslide event, which contributed to the heterogeneity of the soil deposits. In the initial deposition area, particles with larger diameters appeared to have flown longer. Materials from different sources mixed, forming more uniform debris. In the run-out area, the particle flow tended to cause large particles to travel further. However, particle disintegration and crushing led to more small particles along the movement paths and the observed characteristic flow distances of very large particles did not increase with the particle diameter, which is different from observations of an idealized granular mass flow.
44
Hruby, J., R. Steeper, G. Evans, and C. Crowe. "An Experimental and Numerical Study of Flow and Convective Heat Transfer in a Freely Falling Curtain of Particles." Journal of Fluids Engineering 110, no. 2 (June 1, 1988): 172–81. http://dx.doi.org/10.1115/1.3243531.
Full textAbstract:
The flow characteristics and convective heat transfer in a freely falling curtain of spherical particles with an average diameter of 650 μm has been studied experimentally and numerically. Both heated and unheated particle flows have been considered. This work is part of a larger study to determine the feasibility of using particles to directly absorb the insolation in a solar central receiver for high temperature applications. The particles of interest are Norton Master Beads™ which are primarily aluminum oxide. Measurements have been made of particle velocity in heated and unheated particle flows, and particle temperature and air temperature in heated particle flows. Comparison of the measurements with calculations has been made for two particle mass flow rates at room temperature and at two initial elevated particle temperatures. Excellent agreement between numerical and experimental results is obtained for particle velocity in the unheated flow. For the heated particles, both data and predictions show the same trends with regard to particle velocity, particle temperature, and air temperature. However, the calculations of these quantities overpredict the data. The results suggest that the drag coefficient in flows where the particles are hot compared to the air is larger than predicted using conventional methods to account for nonisothermal effects. The prediction of particle temperature and air temperature attained with a drag coefficient that is larger than the standard drag coefficient agrees well with the data.
45
Farivar, Foad, Hu Zhang, Zhao F. Tian, Guo Q. Qi, and Stefan Lukas. "Capturing particle-particle interactions for cylindrical fibrous particles in different flow regimes." Powder Technology 330 (May 2018): 418–24. http://dx.doi.org/10.1016/j.powtec.2018.02.050.
Full text
46
Liu, S., L. M. Russell, D. T. Sueper, and T. B. Onasch. "Organic particle types by single-particle measurements using a time-of-flight aerosol mass spectrometer coupled with a light scattering module." Atmospheric Measurement Techniques 6, no. 2 (February 1, 2013): 187–97. http://dx.doi.org/10.5194/amt-6-187-2013.
Full textAbstract:
Abstract. Chemical and physical properties of individual ambient aerosol particles can vary greatly, so measuring the chemical composition at the single-particle level is essential for understanding atmospheric sources and transformations. Here we describe 46 days of single-particle measurements of atmospheric particles using a time-of-flight aerosol mass spectrometer coupled with a light scattering module (LS-ToF-AMS). The light scattering module optically detects particles larger than 180 nm vacuum aerodynamic diameter (130 nm geometric diameter) before they arrive at the chemical mass spectrometer and then triggers the saving of single-particle mass spectra. 271 641 particles were detected and sampled during 237 h of sampling in single-particle mode. By comparing timing of the predicted chemical ion signals from the light scattering measurement with the measured chemical ion signals by the mass spectrometer for each particle, particle types were classified and their number fractions determined as follows: prompt vaporization (46%), delayed vaporization (6%), and null (48%), where null was operationally defined as less than 6 ions per particle. Prompt and delayed vaporization particles with sufficient chemical information (i.e., more than 40 ions per particle) were clustered based on similarity of organic mass spectra (using k-means algorithm) to result in three major clusters: highly oxidized particles (dominated by m/z 44), relatively less oxidized particles (dominated by m/z 43), and particles associated with fresh urban emissions. Each of the three organic clusters had limited chemical properties of other clusters, suggesting that all of the sampled organic particle types were internally mixed to some degree; however, the internal mixing was never uniform and distinct particle types existed throughout the study. Furthermore, the single-particle mass spectra and time series of these clusters agreed well with mass-based components identified (using factor analysis) from simultaneous ensemble-averaged measurements, supporting the connection between ensemble-based factors and atmospheric particle sources and processes. Measurements in this study illustrate that LS-ToF-AMS provides unique information about organic particle types by number as well as mass.
47
Zeng, Zhuo Xiong, Zhang Jun Wang, and Yun Ni Yu. "Effect of Particle Finite Size on Gas Turbulent Flow." Advanced Materials Research 516-517 (May 2012): 752–57. http://dx.doi.org/10.4028/www.scientific.net/amr.516-517.752.
Full textAbstract:
Dynamic mesh and moving wall technique were employed to simulate the unsteady flow field of moving particle with finite size. For freely moving particle, it does not come into being particle wake. Middle particle can move straightforward outlet, but left and right particles move disorderly in a restricted region. Vortex location varies with the change of particle location. Turbulence energy and pressure is decreased gradually from inlet to outlet. But for moving particle with slip velocity between gas and particle, particle wake comes into being. Turbulence enhancement by particle wake effect is studied by numerical simulation of gas turbulent flows passing over particle under various particle sizes, inlet gas velocities, gas viscosity, gas density and the distance of particles.
48
al-Khayat, Omar, Are Magnus Bruaset, and Hans Petter Langtangen. "Particle Collisions in a Lumped Particle Model." Communications in Computational Physics 10, no. 4 (October 2011): 823–43. http://dx.doi.org/10.4208/cicp.290110.261110a.
Full textAbstract:
AbstractThis paper presents an extension of the lumped particle model in [1] to include the effects of particle collisions. The lumped particle model is a flexible framework for the modeling of particle laden flows, that takes into account fundamental features, including advection, diffusion and dispersion of the particles. In this paper, we transform a binary collision model and concepts from kinetic theory into a collision procedure for the lumped particle framework. We apply this new collision procedure to investigate numerically the role of particle collisions in the hindered settling effect. The hindered settling effect is characterized by an increase in the effective drag coefficient CD that influences each particle in the flow. This coefficient is given by , where ϕ is the volume fraction of particles, is the drag coefficient for a single particle, and n ≃ 4.67 for creeping flow. We obtain an approximation for CD/CD by calculating the effective work done by collisions, and comparing that to the work done by the drag force. In our numerical experiments, we observe a minimal value of n = 3.0. Moreover, by allowing high energy dissipation, an approximation for the classical value for creeping flow, n = 4.7, is reproduced. We also obtain high values for n, up to n = 6.5, which is consistent with recent physical experiments on the sedimentation of sand grains.
49
Ljunggren, M., and L. Jönsson. "Separation characteristics in dissolved air flotation - pilot and full-scale demonstration." Water Science and Technology 48, no. 3 (August 1, 2003): 89–96. http://dx.doi.org/10.2166/wst.2003.0169.
Full textAbstract:
This study presents practical implications for particle separation in Dissolved Air Flotation (DAF). The objectives were to localise where particles are separated from the water phase and to determine what particles, in terms of size, are removed by the DAF-process. Both pilot- and full-scale plants were investigated. Particle sizes were analysed with a light-blocking particle counter and an optical borescope was used for visualisation of particle-bubble aggregates. It was found that particles are preferably separated upstream in the process, i.e. close to the contact zone. Furthermore, separation efficiency for particles increased with increasing particle size.
50
Lv, Bei, Hao Lang, Yao Luo, Wei Zhang, Peize Shi, Bo Wang, Hui Kong, and Xiaodong Hu. "Experimental study on settlement law of multi-particle compound temporary plugging material in rough fracture." IOP Conference Series: Earth and Environmental Science 984, no. 1 (February 1, 2022): 012010. http://dx.doi.org/10.1088/1755-1315/984/1/012010.
Full textAbstract:
Abstract To study the migration and settlement law of temporary plugging particle in fractures, a set of fracture visualization device with controllable pumping rate was built. Based on the experimental device, the influence of the parameters such as pumping rate, particle size combination and adding sequence on the sedimentation and accumulation of temporary plugging particle was studied respectively. The experimental results show that the amount of particle deposition in the fracture is the largest when the pumping rate is 0.04 m3⋅min-1; Under different particle size combinations, 3 mm particles settle earlier than 1 mm particles and the volume of the accumulation is proportional to the proportion of 3 mm particles. The effect of the sequence of addition on the morphology of the particle accumulation is mainly reflected in the layering of the accumulation. When the 3 mm particles are added first and then the 1 mm particles are added, the accumulation volume is larger and the particles settle more. In summary, when a combination of 0.04 m3⋅min-1 rate and 3 mm: 1 mm=4:2 particle size is selected, and 3 mm is added first, and then 1 mm particles are added, the temporary plugging particle has a larger volume of sedimentation in the fracture.