Particle Paths Research Articles

Calculation of flow in incompressible regenerative turbo-machines with bucket form blades based on the geometry of flow path

Purpose Regenerative flow pumps are dynamic machines with the ability to develop high heads at low flow rates. Simplicity, compactness, stable features and low manufacturing costs make them interesting for many applications in industries. The purpose of this study is to present a new method for calculating the flow through regenerative pumps with bucket form blades to predict the performance curves by a cheap and easy-to-use way. Design/methodology/approach The analysis was carried out based on the geometric shape of a fluid particle trajectory in a regenerative turbomachine. The fluid particle path was assumed to be a helix wrapped into a torus. Loss models were considered and the results of predictions were compared with computational fluid dynamics (CFD) data. Findings The overall trend of performance curves resulted from presented model looked consistent with CFD data. However, there were slight differences in high and low flow coefficients. The results showed that the predicted geometric shape of the flow path with the presented model (a helix wrapped into a torus) was not consistent with CFD results at high flow coefficients. Due to the complexity and turbulence of the fluid flow and errors in the calculation of losses, as well as slip factor, there was a discrepancy between the results of the presented model and numerical simulation, especially in high and low flow coefficients. Originality/value The analysis was carried out based on the geometric shape of a fluid particle trajectory in a regenerative turbomachine with bucket form blades. The fluid particle path was assumed to be a helix wrapped into a torus.

DETECTION AND DISCRIMINATION BETWEEN ALPHA PARTICLES AND PROTONS BASED ON PHONONIC CRYSTALS MATERIALS

Ionizing particles detection based on phonons counting are considered as a growing research point of great interest. Phononic crystal (PnC) detectors have a higher resolution than other detectors. In the present work, we shall prepare a setup of a radiation detector based on a 1D PnC. The PnC detector can be used in detection and discrimination between protons and alpha particles with incident energy 1[Formula: see text]MeV. We have proposed a model capable of filtering the energies of two different ionizing particles (proton and alpha particle) of specific lattice frequencies in steps. Firstly, the high probability of phonons production was found at transmitted energy 5[Formula: see text]KeV from the whole path of protons and alpha particles through a vertical thin sheet made from Mylar and Polymethyl methacrylate (PMMA), respectively. The outgoing elastic waves are subjected to propagate through the proposed PnCs structure (Teflon-Polyethylene)2 that shows the different transmission percentage to each particle. Therefore, the detection and discrimination between ionizing ions were achieved.

Optimization and experimental research on process parameters of the softness consolidation abrasive particles

SCA (softness consolidation abrasive) finishing is a new type of machining method. The dilatancy effect of abrasive particles during processing causes the local accumulation of abrasives particles and leads to scratches on the surface of the workpiece, which in the meantime decreases finishing efficiency. So, microscopic contact mechanic model of abrasive particles is established to analyze the force chain transfer phenomenon. A microscope constitutive model of abrasive particles is established to reflect the microscopic force-displacement relationship between abrasive particles. The force chains net evolution of the abrasive particles with different porosity and the surface stress distribution of workpieces are simulated by PFC3D.The results show that when the porosity exceeds 44%, the internal force chain transmission path of the abrasive particles disappears; the surface stress of workpieces exhibits a periodic distribution. As the porosity increases, the stress amplitude decreases. Finally, the test platform is set up and the laws of porosity and abrasive’s size on surface roughness of workpieces can be concluded after a series of polishing experiments by pneumatic wheels with softness consolidation abrasive. The experiments results show that when the abrasive’s size is 800 and the porosity is 24%, the surface roughness of workpieces is small, and the surface average roughness of workpieces can decrease from 313.744 to 67.11 nm.

Magnetic Field Mapping of the CLAS12 Torus—A Comparative Study Between the Engineering Model and Measurements at JLab

This paper provides an overview of the magnetic field measurement and subsequent electromagnetic re-modeling of the CLAS12 torus during the commissioning of the magnet in the fall of 2016. The CLAS12 detector in Hall B is part of the 12 GeV Accelerator Upgrade project at Jefferson Lab. The torus magnet allows precise determination of particle momenta within a cone ~ (5°-40°) in the forward direction. The ability to do this requires that we know the ∫B·dl of the torus to within an accuracy of 0.5% or better. To achieve this, an accurate model of the field along the particle path is required. The TOSCA code is used to generate a full three-dimensional (3-D) simulation of the magnetic envelope of the magnet as designed. Experimentally, the actual magnetic field within the magnet was surveyed to confirm the model design and to measure the deviation from the ideal case. The magnetic field deviations are attributed to manufacturing variability and assembly tolerances. A final model was created with allowances for these deviations guided by the survey data to create a more precise field integral model, which greatly improves the momentum resolution capability, allowing it to deliver the required specifications.

Influence of Harmonic Perturbation on Speed of Billiard Particle as Combination of Deterministic Acceleration and White Noise

Chaotic system under influence of harmonic force is considered. Namely, the motion of Fermi-accelerated billiard particles interacting with scatterers with harmonically oscillating boundaries is investigated. The domain of main parameters in which the acceleration of particles does not depend on the period of scatterers oscillations is found. In this domain, the effect of such oscillations can be considered as an impact of white Gaussian noise whose intensity depends only on the amplitude of velocity of scatterer oscillations and the mean free path of particles. The results of numerical simulations are in good agreement with the results of analytical considerations.

Ghostpeakons and Characteristic Curves for the Camassa-Holm, Degasperis-Procesi and Novikov Equations

We derive explicit formulas for the characteristic curves associated with the multipeakon solutions of the Camassa-Holm, Degasperis-Procesi and Novikov equations. Such a curve traces the path of a fluid particle whose instantaneous velocity equals the elevation of the wave at that point (or the square of the elevation, in the Novikov case). The peakons themselves follow characteristic curves, and the remaining characteristic curves can be viewed as paths of 'ghostpeakons' with zero amplitude; hence, they can be obtained as solutions of the ODEs governing the dynamics of multipeakon solutions. The previously known solution formulas for multipeakons only cover the case when all amplitudes are nonzero, since they are based upon inverse spectral methods unable to detect the ghostpeakons. We show how to overcome this problem by taking a suitable limit in terms of spectral data, in order to force a selected peakon amplitude to become zero. Moreover, we use direct integration to compute the characteristic curves for the solution of the Degasperis-Procesi equation where a shockpeakon forms at a peakon-antipeakon collision. In addition to the theoretical interest in knowing the characteristic curves, they are also useful for plotting multipeakon solutions, as we illustrate in several examples.

Particles in the lungs of patients with chronic bronchitis—part 1: deposition modeling

Background: Chronic bronchitis represents a lung disease which is characterized by a non-reversible reduction of the airway calibers and, as a consequence of that, by a continuous widening of the terminal lung structures. In the present contribution the behavior of inhaled particles in bronchitis lungs is submitted to a detailed theoretical investigation, thereby using a well-validated deposition model. Methods: Any changes of the bronchial airway architecture and alveolar region were modeled by application of well-defined scaling procedures, where random reductions of tubular and spherical diameters are considered. Transport and deposition of particles were simulated by using a random-walk approach including the Monte Carlo method. For the computation of random particle paths a stochastic lung architecture was assumed. Particle deposition was modeled with the help of empirical and analytical formulae describing the physical mechanisms exerting on the particulate substances. Simulations were carried out for male adult lungs and two different breathing conditions. Results: With regard to submicron particles differences of total deposition between bronchitis patients and healthy controls range from 5% to 10%. In the case of particles exceeding a size of 1 µm these discrepancies may be increased to 20%. For most particle sizes chronic bronchitis results in a significant enhancement of tubular (= bronchial + ductal) and alveolar deposition. A change of the breathing conditions from sitting inhalation to light-work inhalation has only minor consequences for total and regional deposition, whereby small particles ( Conclusions: Based on the theoretical results presented in this study it may be concluded that particle deposition is remarkably increased in bronchitis patients with respect to healthy controls. Detailed knowledge of these modifications may be regarded as essential basis for the optimization of inhalation therapies, where high amounts of inhaled aerosol particles have to be delivered to respective target regions.

Collapse of particle-laden buoyant plumes

Particle loading affects the dynamics of buoyant plumes, since the difference between particle and fluid densities is much greater than that in the fluid alone. In stratified environments, plume rise is density limited; after initial overshoot, the plume reaches a terminal level and spreads radially. Particles dropping from this horizontal intrusion may be re-entrained. This recycling of dense matter reduces plume buoyancy and intrusion height and, for sufficient load, can lead to plume collapse. Entrainment-based formulae yield a steady-state plume rise. We identify a new conserved quantity for such plumes. Integrating paths of particles dropping from the intrusion yields the fraction re-entrained. A simple mathematical model predicts from buoyancy ratio at source ($P=$ negative particle buoyancy divided by positive fluid buoyancy) whether a particle-laden plume will collapse. Under this model, for small settling velocity, a particle-laden plume will not collapse if $P<0.368$. Above this, collapse depends also on the amount of particle-free ambient fluid entrained in the overshoot region. For pure plumes, experimental evidence suggests that this is small. For forced plumes, more substantial overshoot and entrainment is shown to increase the critical ratio. An extension, based on successive recycling, estimates time to collapse. To investigate further we develop a simple computational model, coupling a ‘top-hat’ plume model, an analytical formula for radially decaying concentrations in the intrusion and an axisymmetric finite-volume solution for time-dependent settling and entrainment. The model can predict the impact of particle load on final rise, as well as the occurrence and time scales of plume collapse.

Colloid transport and distribution in the hyporheic zone

AbstractColloids moving from the stream into the hyporheic zone may have a negative impact on aquatic ecosystems as they are potential contaminants or carriers of contaminants. Moreover, retained colloids in the hyporheic zone could not only reduce the exchange flux between the stream and streambed but also change the conditions of the bed, affecting the habitats for aquatic organisms. Previous studies focused on the exchange flux across the sediment–water interface, but the colloid transport processes and distribution of retained colloids in the streambed have received little attention. We conducted experiments within a laboratory flume to examine these processes in a streambed driven by bedform‐induced hyporheic flow. Retained colloids measured in the bed at the end of the experiments revealed colloid retention mainly in the shallow layer of hyporheic zone (0–5 cm below the interface). The results demonstrated significant effects of particle trapping and settling on the colloid transport and distribution in the streambed. Retention leads to the formation of a colloid‐filled shallow layer in the bed. Particle paths based on model simulations showed that colloid settling in pore water modifies the direction of colloid transport and allows the colloid particles to move more deeply in the bed.

A Comprehensive Study and Optimization of Magnetic Nanoparticle Drug Delivery to Cancerous Tissues via External Magnetic Field

Abstract Magnetic drug delivery to cancerous tissue as a noninvasive method is a promising cancer therapy. Several complex phenomena and parameters are involved in guiding nanoparticles to the targeted tissue and guaranteeing a predetermined distribution. A comprehensive Euler–Lagrangian method is utilized to simulate a realistic process of nanoparticle delivery and deposition in a cancerous tissue. Non-Newtonian and conductive blood flow in a typical vessel through a cancerous tissue in the presence of an external magnetic field is numerically modeled (both Lorentz and magnetization forces are considered). The cancerous tissue is assumed to be a multizone region with necrotic and live cell blocks. The effect of blood delivery to tissue cells via capillary vessels and blood drainage by the lymphatic system is taken into account. Particle paths and deposition are obtained using the contribution of all forces involved. The effects of Reynolds number (Re), magnetic number, addition of second magnetic source, and distribution of particles are also investigated. For all investigated conditions, the optimum magnetic number to maximize deposition is obtained.

Using 3D kinematic models in subduction channels. The case of the Chañaral tectonic mélange, Coastal Cordillera, northern Chile

The Chañaral tectonic mélange (northern Chile) is a local unit within the late Paleozoic accretionary complex formed at the southwestern margin of Gondwana. The structural characteristics of the studied mélange were mostly developed during a first deformation phase (D1) and include a block-in-matrix fabric, lineations (L1) and foliations (S1), tight to intrafoliar folds, S-C and S-C-C′ composite planar fabrics, and a conspicuous spatial separation of domains with predominantly linear and linear-planar fabrics. Folding during a second stage (D2) modified the orientation of the previous fabrics and structures. The eastern boundary of the Chañaral mélange is N-S to NNW-SSE oriented, moderately dipping to the east. Its western boundary is not exposed. The plane showing the maximum structural asymmetry (the vorticity normal section) is ENE-WSW directed, and sub-vertical. Kinematic criteria consistently reveal top-to-the-WSW displacement. A kinematic model of triclinic transpression with inclined extrusion has been applied to evaluate the D1 structural features of the Chañaral mélange. The pitch of the simple shear direction on the deformation plane ranged from 60°N to 90°. The pitch of the estimated extrusion direction was of 30°-40°S. The coaxial component was clearly constrictional (logarithmic K value of 2 to 5). The vorticity number has not been constrained by the model, but its spatial variation can explain the domainal distribution of the fabrics in the mélange. The simulated particle paths show the predominance of material displacement parallel to the margin, with low to moderate down-dip displacements, which is in accordance with the low-pressure metamorphic assemblages found in the mélange. The convergence direction between the blocks separated by the mélange unit was N50°-60°E. Kinematic blocking of the Chañaral mélange, probably related to the accretion of an oceanic volcanic domain, allowed the D2 folding of the previous structures, a process that, at least initially, proceeded without a change in the convergence direction.

The Effect of Diffusion on the Sedimentation Rate of Soil Microparticles

The submitted paper presents the results of the experiment aimed at quantifying the effect of diffusion on the sedimentation rate of soil microparticles of different fractions. The goal of the experiment was to specify the determination of the texture composition of soils. The textural composition of the soil gives basic information about its hydrophysical properties. Standard methods for determination of granulometric soil composition are based on sedimentation methods. Measuring errors occur in the measurement of the soil microparticle rate, which are usually made of clay particles. Their source is the effect of diffusion. In the settling process with the gradual formation of the colloidal dispersion system, the deposition rate decreases. The rate of sedimentation of the dispersion particles approaches the rate of the mean diffusion feed in the opposite direction. Gradually, the state of dynamic sedimentation equilibrium occurs. The dispersion ratio was in dispersed system formed by clay soil particles from the Senne site. The dispersed medium was distilled water. Grain analyzes were performed by a laser diffraction method on a Mastersizer 2000 from MALVERN Instruments. The soil microparticles’ rates were measured on the basis of the time and the path of particles with diameter d (90). The output of the experiment is the diffusion coefficient, diffusion average feed and sedimentation rate for soil particles of different sizes. The results of the work show that with size of sedimented soil particles, the effect of diffusion increased. On this basis, it is possible to verify the lower limit of the results of grain size analyzes based on the sedimentation method. The results of the work show that the reduction of the size of the settled soil particles increases the effect of diffusion. On this basis, it is possible to quantify the lower limit of the results of grain size analyzes based on the sedimentation method and the particle size at which dynamic sedimentation equilibrium occurs.

Unsupervised Learning Grouping-Based Resampling for Particle Filters

Conventional resampling for particle filters suffers from discarding much potentially useful information due to using less information of spatial distribution of sampling particles set. An unsupervised learning grouping based resampling for particles filter, which could further exploits the relevant spatial information hidden in sampling particles set, was proposed. The core of our approach is that the k-means clustering algorithm is used to automatically form clusters of similar particles, instead of simple heuristic partitioning of the particles set in the spatial domain. Based on the time series analysis between the particle path and observation path for all particles in each cluster, the particle called important particle that has highest temporal correlation is chosen. The diversity of resampling particles set is strengthened by adding important particles to improve the residual resampling. Additionally, by the Kolmogorov-Smirnov two-sample test, we proof that the particles set resampled by the proposed algorithm and the original particles set come from the same distribution function. Extensive experimental results on two numerical models show that the estimation accuracy of particle filter can be improved in this way.

Brzine čestica praha u plazmi na niskom pritisku

Low pressure of inert gas in the vacuum chamber significantly affects the transfer of plasma particle velocity onto powder particles, residence time of powder particles in plasma and the kinetic energy of molten particles before the collision with the substrate. In addition to low pressure of inert gas in the vacuum chamber, the size and mass density of powder particles, together with plasma arc power, have the biggest impact on the average velocity of powder particles. To measure the velocity of powder particles in the vacuum chamber at low pressure, a laser speedometer is applied.The average velocity of molten powder particles V=s/t is calculated when the length of the path of powder particles that pass between two focus distances of the laser beam is divided by the time of particle passage between the two focuses. Measurements are done for vacuum chamber pressure, the values of which are usually from 6.7 to 80 kPa. The paper describes the relationship between the average velocity of Al2O3 and W powder particles and the vacuum chamber pressure, granulate distribution, mass density and plasma arc power. It was found that, for powder of lower mass density, the average velocity of particles can increase for 200 m/s with a decrease in chamber pressure.The effect of pressure on W particles of larger mass density is lower but still important, because a decrease in pressure increases the average velocity of particles up to 50%. Reducing plasma arc power reduces the maximum velocity of both types of powder particles. .

Silicon Nanoparticles in Graphene Sponge for Long-Cycling-Life and High-Capacity Anode of Lithium Ion Battery

A microwave plasma enhanced chemical vapor deposition (MPECVD) method is used to synthesize nanocarbon structures on silicon particles. The structure is analyzed by scanning electron microscope (SEM), Raman spectroscopy and X-ray diffractometer (XRD). The results show that silicon particles are surrounded by wall-like nanographite and multilayer graphene, also known as graphene nanowalls (GNWs). The nanocarbon structures provide excellent chemical and electrochemical properties and good electrical conductivity enabling much improved performance of lithium ion batteries (LIBs) anode made of nanocarbon coated silicon particles. LIBs maintain the high capacity of 2000 mAh/g for 100 cycles of charging and discharging exhibiting very little decrease in capacity. Graphene nanowalls provide multiple conductive paths for silicon particles to remain being electrically connected to the external circuits allowing lithium ions and electrons to enter and leave silicon particles for charging and discharging.

Exact Pollard-like internal water waves

In this paper we construct a new solution which represents Pollard-like three-dimensional nonlinear geophysical internal water waves. The Pollard-like solution includes the effects of the rotation of Earth and describes the internal water wave which exists at all latitudes across Earth and propagates above the thermocline. The solution is provided in Lagrangian coordinates. In the process we derive the appropriate dispersion relation for the internal water waves in a stable stratification and discuss the particles paths. An analysis of the dispersion relation for the constructed model identifies one mode of the internal water waves.

On an Elliptic Free Boundary Problem and Subsonic Jet Flows for a Given Surrounding Pressure

This paper concerns compressible subsonic jet flows for a given surrounding pressure from a two-dimensional finitely long convergent nozzle with straight solid wall, which are governed by a free boundary problem for a quasilinear elliptic equation. For a given surrounding pressure and a given incoming mass flux, we seek a subsonic jet flow with the given incoming mass flux such that the flow velocity at the inlet is along the normal direction, the flow satisfies the slip condition at the wall, and the pressure of the flow at the free boundary coincides with the given surrounding pressure. In general, the free boundary contains two parts: one is the particle path connected with the wall and the other is a level set of the velocity potential. We identify a suitable space of flows in terms of the minimal speed and the maximal velocity potential difference for the well-posedness of the problem. It is shown that there is an optimal interval such that there exists a unique subsonic jet flow in the space iff the length of the nozzle belongs to this interval. Furthermore, the optimal regularity and other properties of the flows are shown.

English

The regional ocean circulation along the Southern Senegal shelf is studied using a numerical model for varying forcing fields during the upwelling season (November-May). The main objective is to study the shelf circulation of the marine environment in the Southern Senegal Upwelling Shelf (SSUS), the Lagrangian pathways by which waters are transported to the surface in the upwelling tongue and the fate of these waters. Model results are compared with hydrographic measurements during UPSEN2-ECOAO survey and satellite images datasets. The upwelling source waters and also the warm nearshore waters are analyzed, from a Lagrangian point of view, by computing the paths of particles that are passively advected by the regional ocean model velocity field (ROMS). It was found that the model is capable of representing the main characteristics of the SSUS whose Sea Surface Temperature (SST) patterns and their variability have an important similarities but the assessment of the current simulated by the model is less obvious because of the few available observations. The present results suggest that high frequency of wind has a strong influence over the mesoscale patterns of the cross-shore circulation in association with local topography and the presence of the Cape Verde peninsula. These cross-shore circulations are dominated by an onshore flow around 14.5°N and an offshore flow around 14.1°N. The onshore flow is in agreement with the previous eulerian studies regarding the coastal divergence of the surface flow (upwelling) that was strongly localized within a few tens of kilometers south of the Cape Verde in the Hann Bight. Lagrangian experiments show also very clearly that coastal warm waters are upwelling waters that were advected from Hann Bight and underwent a strong warming by the heat flux from the atmosphere to the ocean in a shallow area (∼10 m); therefore, easy to warm up. All numerical solutions have shown a tendency of upwelling particles remaining on the shelf for more than a month. These results may explain the enrichment of water in the SSUS and suggest the need to consider the whole shelf as a retention area.   Key words: Upwelling, ocean circulation, modeling, coastal dynamics, shelf, ROMS. &nbsp

Measurement of the thickness of B4C layers deposited over metallic grids via multi-angle neutron radiography

At the present time, different kinds of thermal neutron detectors are under development at the European Spallation Source research facility, in order to overcome the well-known problem of the 3He shortage. One of these new systems relies on the use of a 3D neutron converter cathode that consists of a stack of aluminum grids, covered by a 0.9 µm 10B enriched boron carbide layer (10B4C). As the conversion efficiency is a function of the boron thickness and the mean free path of the charged particles produced in the neutron induced reaction, the characterization of the boron carbide layer uniformity over the grids becomes crucial. In this work, a non-destructive method to map the thickness distribution of the converter layer over the grids is shown. The measurements exploit the white-beam neutron radiography technique where the specimen is irradiated at different angles. This experiment has been performed at the IMAT beamline operating at the ISIS spallation neutron source (UK). The results confirm that this non-destructive, wide-ranging technique allows a reliable and fast sample characterization and that it may be exploited in similar analyses where equivalent requirements are requested.

Semi-analytical modeling of non-premixed counterflow combustion of metal dust

In this study, a semi-analytical model is developed for non-premixed combustion of metal dusts in counterflow configuration. Combustion domain is divided into three separate zones, each of which possesses corresponding mass and energy conservation equations as well as boundary and jump conditions. Metal dust, assumed to be aluminum, undergoes an Arrhenius-type reaction with oxidizer, when it is heated enough to reach the ignition temperature. Dimensionless forms of conservation equations are derived and utilized to elucidate the combustion characteristics. The effects of oxidizer Lewis number and fuel mass concentration on the flame position and temperature are discussed thoroughly. In addition, temperature distribution of the whole domain is calculated by numerically solving the system of partial differential equations. In order to track particles through combustion domain, Lagrangian equations of motion are solved either mathematically or numerically, considering thermophoretic, weight, buoyancy and drag forces. The effects of thermophoretic force on the particle path are investigated, and the deviation of particle from carrier neutral gas direction is obtained. The results showed a great agreement with the data reported in the literature highlighting the fact that the presented model is an efficient one to accurately model the non-premixed counterflow combustion of metal dust.