Numerical Simulation Of Particle Transport Research Articles

Numerical research on the particle transport and deposition in the impingement-film cooling passage

With the aim of exploring the particle transport and deposition characteristics in the internal cooling channel of turbine blades, the computational fluid dynamics-discrete element method is used to implement the numerical simulation of particle transport and deposition in the impingement-film cooling passage. First, the unsteady development process of the particle transport and deposition with the increase in injection particle mass is obtained. Then, the effect of jets Reynolds number, particle Stokes number, and initial particle volume fraction on the particle deposition characteristics is presented. Finally, the particle deposition mechanism in the impingement-film cooling passage of turbine blades is revealed. The results show that the conical-shape particle deposition layer is formed at the impingement stagnation point region and the banded-shape particle deposition layer is formed between adjacent impingement holes. The cooling gas carrying particles is injected from the impact hole and subjected to the fluid shear force. Then, the cooling gas carrying particles gradually developed into the conical-shape free jets. In addition, the symmetrical vortex structure is formed due to the collision of the adjacent jets. Therefore, the particle deposition layer is formed on the impingement target surface, which is caused by the energy attenuation due to the continuous collision of the particle with the particle and the particle with the wall. The increase in the jets Reynolds number inhibits the particle deposition behavior, and the increase in the Stokes number accelerates the particle deposition behavior.

A high fidelity general purpose 3-D Monte Carlo particle transport program JMCT3.0

JMCT is a large-scale, high-fidelity, three-dimensional general neutron–photon–electron–proton transport Monte Carlo software system. It was developed based on the combinatorial geometry parallel infrastructure JCOGIN and the adaptive structured mesh infrastructure JASMIN. JMCT is equipped with CAD modeling and visualizes the image output. It supports the geometry of the body and the structured/unstructured mesh. JMCT has most functions, variance reduction techniques, and tallies of the traditional Monte Carlo particle transport codes. Two energy models, multi-group and continuous, are provided. In recent years, some new functions and algorithms have been developed, such as Doppler broadening on-the-fly (OTF), uniform tally density (UTD), consistent adjoint driven importance sampling (CADIS), fast criticality search of boron concentration (FCSBC) domain decomposition (DD), adaptive control rod moving (ACRM), and random geometry (RG) etc. The JMCT is also coupled with the discrete ordinate SN code JSNT to generate source-biasing factors and weight-window parameters. At present, the number of geometric bodies, materials, tallies, depletion zones, and parallel processors are sufficiently large to simulate extremely complicated device problems. JMCT can be used to simulate reactor physics, criticality safety analysis, radiation shielding, detector response, nuclear well logging, and dosimetry calculations etc. In particular, JMCT can be coupled with depletion and thermal-hydraulics for the simulation of reactor nuclear-hot feedback effects. This paper describes the progress in advanced modeling, high-performance numerical simulation of particle transport, multiphysics coupled calculations, and large-scale parallel computing.

Phase‐resolving direct numerical simulations of particle transport in liquids—From microfluidics to sediment

AbstractThe article describes direct numerical simulations using an Euler–Lagrange approach with an immersed‐boundary method to resolve the geometry and trajectory of particles moving in a flow. The presentation focuses on own work of the authors and discusses elements of physical and numerical modeling in some detail, together with three areas of application: microfluidic transport of spherical and nonspherical particles in curved ducts, flows with bubbles at different void fraction ranging from single bubbles to dense particle clusters, some also subjected to electro‐magnetic forces, and bedload sediment transport with spherical and nonspherical particles. These applications with their specific requirements for numerical modeling illustrate the versatility of the approach and provide condensed information about main findings.

Numerical Simulation of Axisymmetric Plasma Plume Based on Gas–Surface Interaction/Electric Field Coupling

Simulation of the transport of ions and neutral particles is important for studies of the flow field and working characteristics of jet flow plasma devices. The spatiotemporal evolution of plasma plumes in the small space within such devices is complex. To realize numerical simulations of particle transport in this situation, a variety of complex effects need to be considered, such as collisions between particles, chemical reactions, gas–surface interaction, and the electric field. In this study, five types of particles (H <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> , H, metal atoms, <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\text{H}_{2}^{+}$ </tex-math></inline-formula> , and H <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">+</sup> ) are injected into a double-cylinder calculational domain. The direct simulation Monte Carlo (DSMC) method is used to simulate the spatiotemporal evolution of particles in the Maxwell and Cercignani–Lampis–Lord model with different accommodation coefficients. The particle accumulation phenomenon is explained, and the influence of the accommodation coefficient is elucidated. Wall chemical reactions are then introduced to make the gas–surface coupling more realistic. These reactions are found to have a great influence on the particle number density of H <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">+</sup> , H <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> , and H, while the flow field structure has little influence, which is due to the small differences in the particle velocity distributions of each component. Finally, a DSMC/particle-in-cell method is used to simulate a simple axisymmetric example, and the influence of gas–surface interaction, wall chemical reactions, and the electric field on the spatiotemporal evolution of H <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> , H <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">+</sup> , and H in the flow field is demonstrated.

Numerical simulation of particle transport in the urban boundary layer with implications for SARS-CoV-2 virion distribution

This paper presents a description, verification, and application of a model simulating the transport of aerosol particles with different properties in the urban boundary layer by using a Lagrangian approach. The model takes input fields of air flow characteristics from arbitrary external models or analytical solutions and allows estimating the movement, sedimentation, and decay of particles. In this paper, the accuracy of the model is successfully estimated on the basis of exact analytical solutions. Simulations are made for a series of urban canyons under different conditions of stratification and wind speed to assess the effects of these meteorological parameters on particle transport in urban areas. Under similar conditions, the transport of particles simulating SARS-CoV-2 coronavirus particles is calculated.

Upscaling of Anomalous Pore-Scale Dispersion

We study the upscaling of advective pore-scale dispersion in terms of the Eulerian velocity distribution and advective tortuosity, both flow attributes, and of the average pore length, a medium attribute. The stochastic particle motion is modeled as a time-domain random walk, in which particles move along streamlines in equidistant spatial steps with random velocities and thus random transition times. Particle velocities describe stationary spatial Markov processes, which evolve along streamlines on the mean pore length. The streamwise motion is projected onto the mean flow direction using tortuosity. This upscaled stochastic particle model predicts accurately the (non-Fickian) transport dynamics obtained from direct numerical simulations of particle transport in a three-dimensional digitized Berea sandstone sample. It captures all aspects of transport and sheds light on the dependence of the upscaled transport behavior on the flow heterogeneity and the initial particle distribution, which are critical for the accurate modeling of dispersion from the pre-asymptotic to asymptotic regimes.

Pore-scale direct numerical simulation of particle transport in porous media

A computational platform for direct numerical simulation of fluid-particle two-phase flow in porous media is presented in this study. In the proposed platform, the Navier-Stokes equations are used to describe the motion of the continuous phase, while the discrete element method (DEM) is employed to evaluate particle-particle and particle-wall interactions, with a fictitious domain method being adopted to evaluate particle-fluid interactions. Particle-wall contact states are detected by the ERIGID scheme. Moreover, a new scheme, namely, base point-increment method is developed to improve the accuracy of particle tracking in porous media. In order to improve computationally efficiency, a time splitting strategy is applied to couple the fluid and DEM solvers, allowing different time steps to be used which are adaptively determined according to the stability conditions of each solver. The proposed platform is applied to particle transport in a porous medium with its pore structure being reconstructed from micro-CT scans from a real rock. By incorporating the effect of pore structure which has a comparable size to the particles, numerical results reveal a number of distinct microscopic flow mechanisms and the corresponding macroscopic characteristics. The time evolution of the inlet to outlet pressure-difference consists of large-scale spikes and small-scale fluctuations. Apart from the influence through direct contacts between particles, the motion of a particle can also be affected by particles without contact through blocking a nearby passage for fluid flow. Particle size has a profound influence on the macroscopic motion behavior of particles. Small particles are easier to move along the main stream and less dispersive in the direction perpendicular to the flow than large particles.

Three-Dimensional Numerical Study of Particle Trajectory in Particle Charge and Size Analyzer Considering the Effects of System Parameters

In this study, for the purpose of the optimization of the measurement system performance, a three-dimensional numerical model of the particle charge and size analyzer (PCSA) is presented. The PCSA is capable of simultaneous particle size and charge measurement using phase Doppler anemometry. Numerical simulations of particle transport under the influence of the square-wave excitation field have been carried out to identify the optimal PCSA system configurations, improve the particle detection rate, and minimize the measurement bias due to experimental conditions. For the first time, the three-dimensional (3-D) numerical model was used to study the effects of excitation frequency, magnitude of the electric field, and particle inlet velocity on the particle detection rate and charge and size measurement bias. The airflow and the particle motion in the measurement cell were investigated using commercial FLUENT 14.5 software and the particle detection and validation algorithm was implemented in MATLAB. The particle phase was modelled using the Lagrangian approach. The effect of the electric field on particle trajectories was analyzed by solving a coupled system of the electric field and particle transport equations using the User-Defined-Functions (UDFs) in FLUENT. The model was validated by comparing the numerical results with reported experimental data. This 3-D numerical simulation provides a valuable insight into various tradeoffs between the detection rate of particles with different electrical mobility levels and the PCSA parameters. The numerical simulation results demonstrate that the reduction of the measurement bias of particle charge and size distribution can be achieved while maintaining high particle detection percentage by an appropriate selection of system parameters, leading to a more representative profile of measured aerosols. It is shown that the optimal ranges of the excitation frequency, magnitude of electric field, and particle velocity at inlet are between 40 – 50 Hz, 0.3 – 0.4 MV/m, and 0.01 – 0.03 m/s, respectively.

Divergence-free condition in transport simulation

Abstract In this work, two adaptations of the particle method allowing one to reduce the numerical errors induced by the non-zero divergence of flow fields in the numerical simulations of particle transport are presented. The first adaptation is based on the renormalization method allowing one to use an irregular distribution of particles induced by the non-zero divergence of flow fields. The second adaptation consists in applying a correction on the weight of the particles by using the relation between the divergence of flow fields and the particles' volume evolution. This adaptation may be considered as a relaxation method. The accuracy of both methods is evaluated by simulating the transport of an inert tracer by the flow of a jet in crossflow whose concentration fields were measured experimentally. The comparison between the numerical and experimental results shows clearly that the two adaptations of the particle method correct efficiently the effect of a non-zero divergence velocity field on the computed concentration.

Effective dispersion and separation resolution in continuous particle fractionation

Theoretical models and experiments suggest that the transport of suspended particles in microfluidics-based sorting devices can be modeled by a two-dimensional effective advection-diffusion process characterized by constant average velocity, $$\mathbf {W}$$ , and a typically anisotropic dispersion tensor, $$\mathbb {D}$$ , whose principal axes are slanted with respect to the direction of the effective velocity. We derive a closed-form expression connecting the effective transport parameters to separation resolution in continuous particle fractionation. We show that the variance of the steady-state particle concentration profile at an arbitrary cross-section of the device depends upon a scalar dispersion parameter, $$D_\mathrm{eff}$$ , which is primarily controlled by the projection of the dispersion tensor onto the direction orthogonal to $$\mathbf {W}$$ . Numerical simulations of particle transport in a Deterministic Lateral Displacement device, here used as a benchmark to illustrate the practical use of the effective transport approach, indicate that sustained dispersion regimes typically arise, where the dispersion parameter $$\mathcal {D}_\mathrm{eff}$$ can be orders of magnitude larger than the bare particle diffusivity.

Numerical Simulation of Particle Transport and Deposition in the Pulmonary Vasculature

To quantify the transport and adhesion of drug particles in a complex vascular environment, computational fluid particle dynamics (CFPD) simulations of blood flow and drug particulate were conducted in three different geometries representing the human lung vasculature for steady and pulsatile flow conditions. A fully developed flow profile was assumed as the inlet velocity, and a lumped mathematical model was used for the calculation of the outlet pressure boundary condition. A receptor-ligand model was used to simulate the particle binding probability. The results indicate that bigger particles have lower deposition fraction due to less chance of successful binding. Realistic unsteady flow significantly accelerates the binding activity over a wide range of particle sizes and also improves the particle deposition fraction in bifurcation regions when comparing with steady flow condition. Furthermore, surface imperfections and geometrical complexity coupled with the pulsatility effect can enhance fluid mixing and accordingly particle binding efficiency. The particle binding density at bifurcation regions increases with generation order and drug carriers are washed away faster in steady flow. Thus, when studying drug delivery mechanism in vitro and in vivo, it is important to take into account blood flow pulsatility in realistic geometry. Moreover, tissues close to bifurcations are more susceptible to deterioration due to higher uptake.

Model order reduction for numerical simulation of particle transport based on numerical integration approaches

In this article, we present a non-linear model order reduction (MOR) method based on a linearization technique for a model of particle transport. Historically, non-linear differential equations have been applied to model particle transport. Such non-linear differential equations are expensive and time-consuming to solve. This is a motivation for reducing such a model, based on molecular collisions for heavy particle transport in plasma reactors. Here, we reduce the order by linearization with numerical integration approaches and obtain a controllable and calculable transport–reaction model.We linearize the transport model of the heavy particles with numerical fixed point schemes to a general linear control systems (GLCSs); see M.A. Lieberman and A.J. Lichtenberg [Principle of Plasma Discharges and Materials Processing, 2nd ed., Wiley-Interscience, 2005]. Such linearization allows modelling the collision of the plasma reactor by a system of ordinary differential equations; see the models in M. Ohring [Materials Science of Thin Films, 2nd ed., Academic Press, San Diego, CA, 2002]. Because of their non-linearity, we extend the linear splitting methods with linearization techniques to solve these non-linear equations. Numerical simulations are used to validate this modelling and linearization approach.The contribution is to reuse linear reaction models without neglecting the delicate extension to non-linear reaction models. With the help of higher-order quadrature rules, e.g. Simpson’s rule, we obtain sufficient accuracy and replace the non-linear models by a simpler lower-order linear model.Numerical simulations are presented to validate the coupling ideas of the linearized model.

Direct numerical simulation of particle transport by hairpin vortices in a laminar boundary layer

The transport of solid particles by coherent wall structures is studied here. This phenomenon is present in numerous environmental and engineering flows. The flow above a wall-mounted hemisphere is used for generating hairpin vortices in a laminar boundary layer in a controlled way. By means of direct numerical simulation (DNS) of the fluid flow and simultaneous Lagrangian tracking of particles, the influence of hairpin vortices on solid particles released in the wake of the obstacle is analyzed.

Simulated radiation effects in the superinsulating phase of titanium nitride films

This paper investigates possible effects of alpha particle and ion beam irradiation on the properties of the superinsulating phase, recently observed in titanium nitride films, by using numerical simulation of particle transport. Unique physical properties of the superinsulating state are considered by relying on a two-dimensional Josephson junction array as a model of material structure. It is suggested that radiation-induced change of the Josephson junction charging energy would not affect the current-voltage characteristics of the superinsulating film significantly. However, it is theorized that a relapse to an insulating state with thermally activated resistance is possible, due to radiation-induced disruption of the fine-tuned granular structure. The breaking of Cooper pairs caused by incident and displaced ions may also destroy the conditions for a superinsulating phase to exist. Finally, even the energy loss to phonons can influence the superinsulating state, by increasing the effective temperature of the phonon thermostat, thereby reestablishing means for an energy exchange that can support Cooper pair tunneling.

Direct numerical simulations of particle transport in a model estuary

We investigate numerically the mixing of freshwater with ambient saltwater in a model estuary along with associated particle settling processes. We first discuss and specify two numerical setups that consider several relevant features to study the particle settling. The first configuration is a large rectangular basin with a small inlet for the (particle-laden) freshwater; the second is geometrically identical to the first except that the flow is laterally confined to the narrow inlet width. The two flows are computed until a statistically stationary solution is reached. We perform highly resolved direct numerical simulations using a high-order finite difference approach to yield reliable and accurate results. Accordingly, all relevant turbulent scales are resolved and turbulence modeling is not needed. The main target of this study is to describe and illustrate the fluid dynamics and the particle settling processes under the influence of turbulence arising in the freshwater/saltwater-stratified mixing la...

Particle Network Model for Simulating the Filtration of a Microfine Cement Grout in Sand

This paper describes the application of a quasi-one-demensional (1D) network, bubble model to simulate the filtration of a microfine cement suspension injected through a column of sand. The bubble model represents the soil column as a series of homogeneous sites linked through bundles of cylindrical bonds that characterize the distribution of pores. The model captures mechanisms of particle sieving at the inlet sites and infiltration within each of the bonds under the action of hydrodynamic and gravitational forces. The behavior of each bond is based on numerical simulations of particle transport, collection, mounding, and clogging within a cylindrical model pore. Two empirical parameters are introduced to account for uncertainties in particle attachment at the pore wall and observed mechanisms of resuspension of hindered particles. In principal, these parameters can be calibrated from measurements of effluent concentrations. The bubble model provides useful physical insights to explain the transient dyna...

Numerical Simulation of Particle Transport in a Drift Ratchet

The directed transport of microparticles depending on their size is the basis for particle sorting methods that are of utmost importance in, for example, life sciences. A drift ratchet is a Brownian motor that allows for such a directed transport. Hereby, the particle motion is induced by a combination of the Brownian motion and asymmetries stemming, for example, from the domain's geometry, electrical fields, or transient pressure boundary conditions. We simulate a particular drift ratchet which consists of a matrix of pores with asymmetrically oscillating diameter wherein a fluid with suspended particles is pumped forward and backward, and where the particles' long-term transport direction depends on their size. Thus, this setup allows for continuous and parallel particle separation, which has been shown experimentally. However, for a deeper understanding and for an optimized parameters' choice, further investigations, i.e., simulations, are necessary. In this paper, we present first results achieved with our parallel three-dimensional simulation codes applied to a still simplified scenario. This simplification is necessary to isolate different phenomena (e.g., asymmetries and Brownian motion) to check their relevance for the particle transport. The simulation codes are based on (adaptive) Cartesian grids in combination with finite volume and finite element discretizations. Cartesian grids allow for a very efficient implementation of the solver algorithms and an efficient balanced parallelization via domain decomposition. The achieved simulation results show the effectiveness of our approach and give some strong hints on a directed particle transport already with the simplified model we used here.

The Effect of Depletion Layer Thickness in Avalanche Photodiodes for Measurement of Low-energy Electrons

We have tested APDs (Type spl 3989 and Z7966, Hamamatsu Photonics K.K.) using an electron beam. The Z7966, which has a depletion layer of 10 μ m , is firstly focused on and tested in our former paper [K. Ogasawara, K. Asamura, T. Mukai, Y. Saito, Nucl. Instr. and Meth. A 545(3) (2005) 744] for the energy range of 5–20 keV. The result shows that the pulse height distribution of the APD signal exhibits a significant peak for electrons with energies above 8 keV, and positions of their peaks show a good linearity. The condition of the peak production at energies below 8 keV was attributed to the thickness of the dead layer on the surface of APDs. Now we have tuned up our electron acceleration system up to 40 keV, and tested Z7966 by electrons of higher energies. The result shows that the output pulse height distributions of this Z7966 were distorted over 30 keV. In order to examine the distortion of pulse height distributions, we have made a Monte Carlo numerical simulation of particle transport inside the APD. The result shows that the highest energy limit is expected to be determined by the thickness of the depletion layer inside the APD. Therefore, we have tried an APD type spl 3989, which has a thicker depletion layer ( 30 μ m ) and a thinner dead layer. As is expected, the spl 3989 responded to 2–40 keV electrons with fine peaks in the output pulse height distributions. The energy resolution was lower than 1 keV for 2–20 keV electrons, and 5 keV for 40 keV electrons. The linearity of the response was also good. According to the Monte Carlo simulation, electrons up to about 60 keV are expected to be well detectable.

Experimental measurements and numerical simulations of particle transport and distribution in ventilated rooms

Prediction of particle dispersion and distribution in a room is very important for creating and maintaining a healthy indoor environment. The present study used a CFD program with a Lagrangian particle tracking method to predict particle dispersion and concentration distribution in ventilated rooms. Since the Lagrangian method could generate great uncertainty in particle concentration calculations, this study first investigated such uncertainty using a statistical approach. It was found that the stability of the concentration solution became well controlled as a sufficient number of particles were analyzed. Although the overall computational cost was considerable, the numerical results agreed well with associated experimental data. In all cases studied, particle size distribution was monodisperse, and particle diameter ranged from 0.31 to 4.5 μm. Particle deposition rate was neglected, and particles were hence removed only by the ventilation system. Thus the particle removal performance of different ventilation systems can be evaluated. Three ventilation systems have been studied, including ceiling and side wall supply systems and an underfloor air distribution (UFAD) system. It was found that the UFAD system had a better particle removal performance than the ceiling and side wall supply systems in the study. However, resuspended particles at the floor level can still cause problems in an UFAD system.

Electron backscattering from surfaces: Azimuth-resolved distributions

The paper develops an invariant-embedding approach to calculate various distributions of particles reflected from a solid surface. The technique is most efficient for calculations resolving at once multiple variables; in particular, it represents a powerful tool for quantitative surface analysis utilizing reflection electron energy loss spectroscopy and elastic-peak electron spectroscopy data. Based upon deterministic equations, the approach involves no numerical simulations of particle transport and, though less generally applicable, offers significant advantages over the Monte Carlo method in computing speed, accuracy, and resolution. This work generalizes our recent treatment of azimuth-integrated distributions [Phys. Rev. B 68, 155409 (2003)] to those additionally resolved in azimuthal angles. It is a striking feature of the invariant-embedding approach that resolution in the extra variable, and thus much larger extent of the resulting data, require only a moderate (typically, less than a factor of 2) increase in the associated computing time. Within $\ensuremath{\sim}1\phantom{\rule{0.3em}{0ex}}\mathrm{min}$ on a PC, the scheme produces an extremely detailed description of electron backscattering for arbitrarily sophisticated scattering cross sections: various distributions (in the numbers of elastic and/or inelastic collisions, path lengths, polar and azimuthal angles, etc.) are determined for all incidence and emission directions at once. The paper outlines the analytical formalism and discusses specific features of an appropriate calculation scheme. Some of the capabilities and advantages of the present approach are illustrated by calculations of various distributions of 300 and 2000 eV electrons backscattered from Al and Au. Compared to the earlier results, the additional azimuth angle resolution and the possibility to calculate for non-normal electron incidence yield a greater variation in the observed distributions.