Motion Of Dust Particles Research Articles

A Note on the Significance of Quartic Autocatalysis Chemical Reaction on the Motion of Air Conveying Dust Particles

Abstract Little is known on the significance of fluid–particle interaction for velocity and temperature as in the case of centrifuge for separating particles of different types, launching of rockets, and motion of space shuttle through the air when there exist chemical reactions between the flow and the wall. The aim of this study is not only to explore the significance of quartic autocatalytic chemical reaction on the flow of dusty fluid in which the transmission of energy in form of electromagnetic is nonlinear but also to unravel the effects of buoyancy on the velocity of the dust and temperature of the dust. The nonlinear partial differential equations that model the transport phenomenon was transformed, nondimensionalised, and parameterised using suitable variables. The corresponding boundary value problems were converted to an initial value problem using the method of superposition and solved numerically. The outcome of the study indicates that enhancement of buoyancy is a yardstick to increase the vertical velocity, horizontal velocity, and shear stress within the fluid domain; increase the velocity of the dust particles; increase the temperature distribution across the flow of dusty fluid; increase the concentration of dusty fluid; and decrease the concentration of the catalyst. It is worth noticing that utmost velocity of the dust occurs at a minimum value of fluid–particle interaction for velocity in the flow over a larger thickness of paraboloid of revolution.

Research on dust concentration measurement device based on spiral flow

Based on the principle of electrostatic induction, a dust detection device is designed in this paper, aiming at the problems of insensitive detection and slow movement of dust particles in the existing dust measuring devices. Its shape structure is improved on the basis of the existing straight pipe. The air inlet is arranged on the side of the cylindrical pipe wall so that the particles flow through the pipe in a double helix way and the diameter of the main pipe is changed to make the middle part of the pipe shrink. The 3D model of pipeline was established by gambit2.4 and simulated in Fluent6.3. In the improved device, the movement speed of dust particles increases. With the increase of velocity, the probability of friction and collision of dust particles in the side-entry tube is increased, and the induced charge is increased.Therefore, the improved device can effectively improve the accuracy of dust measurement under the condition of low concentration and small particle size.

Dynamics and transport of magnetized two-dimensional Yukawa liquids

Laboratory dusty plasma typically refers to a collection of micron-sized solid dust particles immersed in the plasma environment, as a result, these dust particles are negatively charged to thousands of elementary charges. Due to the electrical shielding provided by free electrons and ions, the interaction between these dust particles can be modeled as the Yukawa potential. These dust particles are strongly coupled due to their high charges, so that they exhibit collective behaviors of solids and liquids. Magnetic fields are often experimentally introduced in the modulation of dusty plasmas, and later the equivalent “magnetized” dusty plasma experiment is performed, so that magnetized Yukawa systems can be experimentally achieved now. Here, we review a series of results of collective behaviors and different transport processes of magnetized two-dimensional (2D) Yukawa liquids from Langevin dynamical simulations. From the obtained spectra of the simulation results, the vibrational density of states has only one dominant peak frequency, which can be analytically expressed as a function of the cyclotron and plasma frequencies, suggesting that the cyclotron motion of dust particles has been coupled with their thermal motion. It is also found that the statistics of particle motion with a strong magnetic field tend to deviate from the classical Maxwellian distribution. When the ratio of the cyclotron and plasma frequencies for dust particles is around the order of unity, the motion of dust particles tends to be superdiffusive. As the magnetic field increases, the shear viscosity increases with the magnetic field when the Yukawa liquid is cold; however, when the Yukawa liquid is hot, the variation trend of shear viscosity is reversed. It is also found that the structural relaxation time and the diffusion coefficient can be described as a power law relationship with two distinct values of the exponent at low and high temperatures, respectively.

Neutral gas in complex plasmas causes friction and affects the dynamics of dust particle systems

Particle simulations of a dust-infused plasma show how friction affects the motion of dust particles in the plasma and highlight regimes that are most affected by dissipation.Particle simulations of a dust-infused plasma show how friction affects the motion of dust particles in the plasma and highlight regimes that are most affected by dissipation.

Enhancement of the electric field in electrodynamic screen using helix electrodes

The effect of electric fields on electrodynamic screen is very important for dust removal from solar cell screen. In this paper, we first analyzed and studied electrodynamic screen and examined the results in comparison with other reports in the literature. Also, simulation was done using the COMSOL Multiphysics software using the finite element analysis (FEA). The simulation results were compared with the results of analytical method (ANA), which are in good agreement with each other. Then, it is proposaled to using the structure of spring-shaped electrodes and the properties of Helix antennas, the electric field at the surface of electrodynamic screen was studied and amplified. In this system, the wired circles are located around the cylindrical electrodes. Found, when the voltage circulates inside these electrodes and wires in the frequency range of 5 to 100 Hz, it increases the electric field by about 50%. The amplification of the electric field leads to a more powerful electric force and a faster movement of dust particles, which speeds up the cleaning of electrodynamic screen.

Micro-dynamics of neutral flow induced dusty plasma flow

We present a detailed experimental study of gas flow induced motion of dust particles in a DC glow discharge plasma. The characteristics of the dust dynamics are investigated as a function of the differential gas flow rate, the background neutral pressure, the dust particle size, and the neutral species of the gas. The experiments have been carried out in the table top Dusty Plasma Experimental (DPEx) device in which a plasma is created between a disk shaped anode and a grounded cathode in a Π-shaped Pyrex glass tube. The asymptotic steady state flow velocity of the injected micron sized dust particles is found to increase with an increase in neutral flow velocity and decrease with an increase in the background pressure. Furthermore, this velocity is seen to be independent of the size of the dust particles, but decreases with an increase in the mass of the background gas. A simple theoretical model, based on estimates of the various forces acting on the dust particles, is used to elucidate the role of neutrals in the flow dynamics of the dust particles. Our experiments thus provide a detailed microscopic understanding of some of the past phenomenological observations of dust flows in the DPEx device and can prove useful in future experimental implementations of dust flow experiments.

Numerical Simulation of Transport and Deposition of Dust Particles in Human Tracheobronchial Airways

Dust is a common pollutant of the air we breath. If dust particles are inhaled and deposited in human airways, they can cause a variety of respiratory disorders. The inhaled dust particles motion in human airways goes along with the airflow. The transport process can be considered as a two-phase flow of a gas phase and a particle phase. In this study, we investigated the airflow and dust particles transport and deposition in human tracheobronchial airways using computational fluid dynamics (CFD) techniques. A steady simulation was performed in asymmetric tracheobronchial airway mode consisting of 19 outlets to observe the characteristics of airflow fields. The discrete phase model (DPM) was employed to predict the particle trajectories and deposition in the airway model. Deposition resulted from inertial impaction and gravitational sedimentation was considered. In the simulation, the airflow characteristics differences in the right and left bronchial trees were observed. The influence of secondary flow on dust particles motion was great. More dust particles were deposited in the right bronchial tree than in the left. The deposition fraction of dust particles in human tracheobronchial airways was high. This study can provide awareness on deposition of dust particles passing beyond the larynx and enhance prevention of their entry into the respiratory system. It can also contribute a convenient way on the location of deposition of particles of a given type in human respiratory tract to be used for respiratory disease preventions.

Investigation of the Dynamics of Solid Particles Moition Into the Ventilated Air Gap of the Cladding Façade Systems

All articles must coTheatmospheric air in cities contains a large number of pollutants in the form of solid particlesand dust. One of the most dangerous not only for humans, but also for building structures, are the particles smaller than 10 microns. They penetrate into the structures of cladding façade systems, fall and settle on the surface ofa insulation made of mineral wool, as well as on metal elements of the façade cladding system, facedinto the ventilated air layer. The author carried out a large number of experimental studies of structures of façade cladding systems, which made it possible to choose the following parameters and characteristics when performing this work.The article deals with the dynamics of the motion of dust particles with a size from 1 to 5 microns in the air interlayer of the claddingfaçade system with the Reynolds number Re ≤ 1. An equation is obtained for calculating the velocity of dust particles in a size of 10-50 µm in the air stream at its rate of 0.1-0.0, 8 m/s at various outside air temperatures, as well as the conditions under which dust particles “levitate” in the air gap are determined. At the same time, “levitating” dust particles settle on the surface of a mineral wool insulation from a stone fibber and penetrate into the thickness of the fibrous insulation, causing a change in its thermal and sorption characteristics.

Numerical Investigation of Two-Phase Mixed Convection Flow of Particulate Oldroyd-B Fluid with Non-Linear Thermal Radiation and Convective Boundary Condition

The present investigation addresses the mixed convection two-phase flow of dusty Oldroyd-B fluid towards a vertical stretching surface in the presence of convective boundary condition and nonlinear thermal radiation. The fluid and dust particles motion is coupled only in the course of drag and heat transfer between them. The Stokes linear drag theory is employed to model the drag force. The numerical solutions based on the Runge-Kutta-Fehlberg 45 scheme with shooting method are presented for both fluid and particle phase velocity and temperature fields. Further, numerical results are obtained for skin friction factor and local Nusselt number of prescribed values of pertinent parameters. The results are presented graphically and the physical aspects of the problem are analyzed. The obtained results are validated with existing results and found to be in good agreement. It is found that the mass concentration of the dust particle parameter plays a key role in controlling flow and thermal behaviour of non-Newtonian fluids.

IMPROVING THE EFFICIENCY OF THE VORTEX DUST COLLECTORS

It is proposed to use a modernized “wet” vortex dust collector for cleaning ventilation emissions from non-adhering dust. The design of the vortex dust collector contributes to its effi ciency by installing irrigation nozzles in the primary and secondary air connections made in the form of a Venturi tube, which allows reducing energy consumption during the cleaning of dusty air. Due to the multidirectional movement of dust particles and splashed water, active coagulation of dust particles and water particles occurs, as well as a liquid fi lm is formed on the inner surface of the separation chamber, which prevents the dust particles from rebounding from the separation chamber and facilitates their collection and washing into a collecting bin.

Large-Scale Transport of Charged Macroparticles Induced by Dust–Acoustic Solitons

We have studied experimentally the oscillatory process in the dusty plasma in the glow discharge stratum. It is shown that the oscillations are induced by the dust–acoustic instability, as a result of which dust–acoustic solitons are excited. The motion of dust particles in the electric field of solitons has been analyzed. It has been established that a soliton leads to a large-scale unidirectional transport of charged particles in the direction of its motion. The experimental results have been interpreted theoretically using the MHD model of the plasma.

Dynamics of Dust Particles of Different Structure: Application to the Modeling of Dust Motion in the Vicinity of the Nucleus of Comet 67P/Churyumov–Gerasimenko

We consider the estimates of the main forces acting on dust particles near a cometary nucleus. On the basis of these estimates, the motion of dust particles of different structure and mass is analyzed. We consider the following forces: (1) the cometary nucleus gravity, (2) the solar radiation pressure, and (3) the drag on dust particles by a flow of gas produced in the sublimation of cometary ice. These forces are important for modeling the motion of dust particles relative to the cometary nucleus and may substantially influence the dust transfer over its surface. In the simulations, solid silicate spheres and homogeneous ballistic aggregates are used as model particles. Moreover, we propose a technique to build hierarchic aggregates—a new model of quasi-spherical porous particles. A hierarchic type of aggregates makes it possible to model rather large dust particles, up to a millimeter in size and larger, while no important requirements for computer resources are imposed. We have shown that the properties of such particles differ from those of classical porous ballistic aggregates, which are usually considered in the cometary physics problems, and considering the microscopic structure of particles is of crucial significance for the analysis of the observational data. With the described models, we study the dust dynamics near the nucleus of comet 67P/Churyumov–Gerasimenko at an early stage of the Rosetta probe observations when the comet was approximately at 3.2 AU from the Sun. The interrelations between the main forces acting on dust aggregates at difference distances from the nucleus have been obtained. The dependence of the velocity of dust aggregates on their mass has been found. The numerical modeling results and the data of spaceborne observations with the Grain Impact Analyzer and Dust Accumulator (GIADA) and the Cometary Secondary Ion Mass Analyzer (COSIMA) onboard the Rosetta probe are compared at a quantitative level.

Large-scale coherent structures of suspended dust concentration in the neutral atmospheric surface layer: A large-eddy simulation study

Dust particles can remain suspended in the atmospheric boundary layer, motions of which are primarily determined by turbulent diffusion and gravitational settling. Little is known about the spatial organizations of suspended dust concentration and how turbulent coherent motions contribute to the vertical transport of dust particles. Numerous studies in recent years have revealed that large- and very-large-scale motions in the logarithmic region of laboratory-scale turbulent boundary layers also exist in the high Reynolds number atmospheric boundary layer, but their influence on dust transport is still unclear. In this study, numerical simulations of dust transport in a neutral atmospheric boundary layer based on an Eulerian modeling approach and large-eddy simulation technique are performed to investigate the coherent structures of dust concentration. The instantaneous fields confirm the existence of very long meandering streaks of dust concentration, with alternating high- and low-concentration regions. A strong negative correlation between the streamwise velocity and concentration and a mild positive correlation between the vertical velocity and concentration are observed. The spatial length scales and inclination angles of concentration structures are determined, compared with their flow counterparts. The conditionally averaged fields vividly depict that high- and low-concentration events are accompanied by a pair of counter-rotating quasi-streamwise vortices, with a downwash inside the low-concentration region and an upwash inside the high-concentration region. Through the quadrant analysis, it is indicated that the vertical dust transport is closely related to the large-scale roll modes, and ejections in high-concentration regions are the major mechanisms for the upward motions of dust particles.

On interstellar light polarization by diamagnetic silicate and carbon dust in the infrared

The motion of diamagnetic dust particles in interstellar magnetic fields is studied numerically with several different sets of parameters. Two types of behavior are observed, depending on the value of the critical number $R$, which is a function of the grain inertia, the magnetic susceptibility of the material and of the strength of rotation braking. If $R\leq10$, the grain ends up in a static state and perfectly aligned with the magnetic field, after a few braking times. If not, it goes on precessing and nutating about the field vector for a much longer time. Usual parameters are such that the first situation can hardly be observed. Fortunately, in the second and more likely situation, there remains a persistent partial alignment which is far from negligible, although it decreases as the field decreases and as $R$ increases. The solution of the complete equations of motion of grains in a field helps understanding the details of this behavior. One particular case of an ellipsoidal forsterite silicate grain is studied in detail and shown to polarize light in agreement with astronomical measurements of absolute polarization in the infrared. Phonons are shown to contribute to the progressive flattening of extinction and polarization towards long wavelengths. The measured dielectric properties of forsterite qualitatively fit the Serkowski peak in the visible.

Behaviour of two‐dimensional liquid dusty plasmas under perpendicular magnetic fields

The collective behaviour of two‐dimensional (2D) liquid dusty plasmas under perpendicular magnetic fields is studied using Langevin dynamic simulations. Based on the positions and velocities of the simulated dust particles, the dynamic parameters of intermediate scattering functions and probability distribution functions are calculated. It is found that, under different 2D liquid dusty plasma conditions, the motion of individual dust particles tends to be more super‐diffusive under stronger perpendicular magnetic fields, well consistent with the previous finding using a different diagnostic technique.

Analysis of influence factors on dust removal efficiency for novel photovoltaic lunar dust removal technology

The deposition of lunar dust on the surface of a lunar probe has an adverse effect on the performance of the equipment. This paper proposes novel lunar dust removal technology, which is triggered by UV light isolated from sunlight, to clean the adhered dust using the high voltage produced by the anomalous photovoltaic effect of lanthanum modified lead zirconate titanate. Based on the equivalent electrical model, the mathematical model of electrostatic field force used for removing lunar dust particles is established. Based on the mathematical model the influencing factors of dust removal efficiency are proposed and analyzed by experiments. To improve the dust removal efficiency, a conductive dust removal electrode is designed, coated with a layer of insulating film to avoid the reciprocating motion of dust particles, and the feasibility of the configuration is proved by experiments.

Dynamics of non-spherical dust in the coma of 67P/Churyumov– Gerasimenko constrained by GIADA and ROSINA data

Among the comet 67P/Churyumov–Gerasimenko (67P/C-G) in situ measurements, the closest that have ever been performed at a comet nucleus, are also those of speed, mass, and crosssection of cometary grains performed by the Grain Impact Analyser and Dust Accumulator (GIADA) instrument. To interpret GIADA data, we performed dust dynamical numerical simulations with both spherical and non-spherical (spheroids) shapes. This allowed us to analyse howthe grain non-sphericity affects the data interpretation.We find that some measured dust speeds are unlikely reproducible when a spherical shape is considered.We considered two GIADA observational periods, 2015 February 19–27 and 2015 March 13–28. Gas parameters calibrated with the Rosetta Orbiter Spectrometer for Ion and Neutral Analysis (ROSINA) measurements have been used to retrieve the gas conditions to set up the dust particle motion. The dust grains are assumed to be out of the near nucleus coma, i.e. where the gas velocity is radial and constant, therefore they are either aligned or have random but constant orientation with respect to the gas drag. We reproduced the GIADA dust speeds, using spheres and two different spheroidal shapes. We find that the particle shapes that reproduce best the GIADA dust speeds are consistent with the particle shape constrained by the GIADA data. We obtain different terminal velocities for spherical and non-spherical particles of the same mass. The shape, which reproduces the GIADA data, is oblate rather than prolate spheroid. We obtain rotational frequencies of the spheroidal particles that best fit the GIADA measurements in these periods.

Flame propagation and dust transient movement in a dust cloud explosion process

In recent years, dust explosion accidents have been reported frequently. More and more studies on dust explosions have been published. However, there are few reports concerning flame propagation and dust particle movement of a large-scale dust explosion process in open space. In this study, a large-scale corn starch dust explosion was simulated using computational fluid dynamics software. Flame propagation and particle transient movement during the explosion were monitored. The initial dust cloud, with a concentration of about 300 g m−3, is approximately an ellipsoid with a 4 m major axis (horizontal) and a 3 m minor axis (vertical); its center is at about 1.5 m distance from the ground. At the time of 700 ms when the explosion process basically finishes, the dust cloud expands to a semi ellipsoid with a 14 m major axis (vertical) and a 10 m minor axis (horizontal). The dust cloud volume expands to 366.92 m3, which is 14.60 times of its initial value (25.13 m3). During the explosion, both the flame and the dust cloud expansion are first accelerated and then decelerated, but overall, variation of dust cloud expansion velocity lags behind the variation of flame velocity. Before 400 ms, dust cloud expansion velocity is notably lower than flame velocity, then dust cloud and flame expand outwards together basically at the same speed, and the distance between dust cloud boundary and flame boundary stabilizes at around 0.5 m.

Design features of vortex dust collectors

This article states that during the construction of industrial buildings it is necessary to provide engineering communications (including systems of supply and exhaust ventilation) which ensure uninterrupted production, its technological and environmental safety. It is necessary to use cleaning devices to remove pollutants from ventilation emissions in local exhaust systems. As for devices for removing highly disperse non-sticky dust, it is possible to offer vortex dust collectors, the efficiency of which depends on the design and operating mode. A method is proposed to increase the efficiency of a vortex dust collector, to improve the quality of the purified air, and to reduce energy consumption during air purification by installing watering nozzles in primary and secondary air pipes made in the form of a Venturi tube. In consequence of multidirectional movement of dust particles and sprayed water, active coagulation of dust particles takes place, as a result of which the separation increases. Apart from that, watering dusty air flows leads to the formation of a liquid film on the inner surface of the separation chamber, which prevents dust particles from rebounding off the separation chamber and facilitates their capture and flushing into the collecting hopper

Test of the Einstein Relation in Dusty Plasmas

We test the Einstein relation $D_{p} =\mu _{p} k_{B} T_{t}$ that connects the diffusion coefficient $D_{p}$ and mobility coefficient $\mu _{p}$ , where $T_{t}$ is the temperature of particles that cause the scattering. The test is performed for a 3-D dusty plasma, using results from a Langevin-Yukawa molecular dynamics simulation. The coefficients $D_{p}$ and $\mu _{p}$ describe the motion of projectile dust particles drifting through a cloud of target particles of a different size due to a constant force. The drift is opposed by collisions with target particles and neutral atoms. The Einstein relation is found to be violated at high driving forces of order $m_{p} \omega _{t}^{2} a$ or stronger, where $m_{p}$ is the projectile mass, while $\omega _{t}$ and $a$ are the plasma frequency and Wigner-Seitz radius of the target particles. Because the Einstein relation fails at high forces, another relation is needed to describe diffusion in terms of mobility. We present a generalized Einstein relation, which we find to be satisfied over a wide range of forces.