Spherical Dust Research Articles

Exploring the potential of heat transfer and entropy generation of generalized dusty tetra hybrid nanofluid in a microchannel

Caputo–Fabrizio time-fractional derivatives are the subject of this paper. This article generalizes the concept of dusty Tetra hybrid nanofluid moving freely via convection between infinite vertical parallel static plates. Free convection and buoyant force cause the flow and transmit the heat. In addition, there is a consistent distribution of spherical dust particles over the whole flow. It is the temperature difference between the two regions that sets off free convection. Free convection takes heat transfer into account. The dust Tetra hybrid nanofluid classical model employs non-dimensional variables to achieve a dimensionless form. We also convert the dimensionally-free model into a fractional generalized dusty Tetra hybrid nanofluid model. In this paper, we use the finite sine approach to analytically solve the governing equations of the generalized Dusty Tetra hybrid nanofluid model. In this article, we generalize the concept of a dust-filled Tetra hybrid nanofluid freely flowing between infinite vertical parallel plates. We found an analytical solution to the governing equations for the generalized dusty Tetra hybrid nanofluid by combining the Finite Sine Fourier and Laplace transforms. Understanding the mechanics of velocity and temperature profiles requires the use of numerical computation for a variety of embedded factors. In-depth statistical analysis and charting of data are features of this investigation. Using Mathcad-15, we plot the profiles of the Tetra hybrid nanofluid, dust particles, and temperatures to see the findings physically. Also determined are the skin friction and Nusselt number. The rate of heat transfer decreases with time, as seen in Table 1. Similarly, as seen in Table 2, raising the fractional parameter results in a higher skin friction. In addition, the energy profile of both velocities increases with increasing tetra hybrid nano fluid volume percent, albeit the fraction's contribution decreases with time. Since the fractional models are more accurate, they also provide more potential outcomes. When all the facts are considered, these choices may out to be the best.

Charged dust in Einstein–Gauss–Bonnet models

We investigate the influence of the higher order curvature terms on the static configuration of a charged dust distribution in EGB gravity. The EGB field equations for such a fluid are generated in higher dimensions. The governing equation can be written as an Abel differential equation of the second kind, or a second order linear differential equation. Exact solutions are found to these equations in terms of special functions, series and polynomials. The Abel differential equation of the second kind is reducible to a canonical differential equation; three new families of solutions are found by constraining the coefficients of the canonical equation. The charged dust model is shown to be physically well behaved in a region at the centre, and dust spheres can be generated. The higher order curvature terms influence the dynamics of charged dust and the gravitational behaviour which is distinct from general relativity.

A review on recent advantages and evaluation of microparticles and their applications

Microparticles are free spherical dust between 1 and 1000 microns made of synthetic, non-biodegradable, and non-biodegradable polymers. There are two types of microparticles: microcapsules and micro matrix. The main types of microparticles are magnetic microparticles, polymer microparticles, bio-adhesive microparticles, biodegradable polymer microparticles, synthetic polymer microparticles, floating microparticles, and radioactive microparticles. The advantage of microcarriers over nanoparticles is that they do not cross the 100 nm interstitium during lymphatic transport and therefore act locally. Toxic substances can be solidified in the form of micro-encapsulated and dried particles. Moreover, methods to characterize numerous physicochemical parameters like drug release, thermal properties, and particle size are introduced, along with new tests like in vitro leaching tests and floating tests.

Dust-ion-acoustic shock waves in the presence of (r, q) distributed electrons

A three-component dusty plasma system, with non-Maxwellian electrons, is investigated. The ions are considered to be mobile, the (spherical) dust is assumed to be stationary with charge- fluctuations, and the electrons follow the generalized velocity distribution function (VDF). The respective Burger’s equation, which manifests a shock structure, is derived by employing a reductive perturbation technique (RPT). It is deduced that dust charge fluctuations induce shock potential in a collisionless plasma system. The resultant perturbed potential is evaluated as affected by different plasma parameters, e.g. the ratios of electron to ion temperature (σ i ) and equilibrium densities (μ), and the non-thermal indices r and q. The shock amplitude is seen to decrease when the value of σ i is increased, and vice versa, whereas an opposite trend is observed for μ. It is found that for r = 0 and increasing values of spectral index q, amplitude of the potential distribution enhances while its width decreases. It is further noted that non-Maxwellian VDF significantly modifies the potential distribution. For the limiting case, namely, r = 0 and q → ∞ , the corresponding Maxwellian results are retrieved which benchmarks our findings. Present work will be useful in understanding the nonlinear propagation of dust-ion-acoustic shock waves in system where non-thermal population—as caused by various physical processes—of electrons are observed.

Near-Field Single-Scattering Calculations of Aerosols: Sensitivity Studies

We model the effects of the photosensitive parameters of aerosols on their optical properties to provide a solid framework for further experimental and theoretical studies. A spherical dust particle is used to study the effects of the ambient medium, size, surface roughness, wavelength, and imaginary part of the complex refractive index. Five Gaussian random spheres with different aspect ratios are simulated to study the dependence of aerosol light scattering properties on particle shape distribution. To investigate the influence of composition, we model two typical kaolinite-like particles (pure and composite) collected from Southwest Sahara, with 0 and 2% hematite at different mixing states. Using the method of discrete-dipole approximation in DDSCAT, a comparative study is performed with the Mueller matrix elements, scattering, absorption, extinction efficiencies, single scattering albedo, and linear depolarization ratio as indicators. For single, microscopic dust particles, near-field calculations are carried out. The results show that the intensity of backscattering and the scattering efficiency decreases in water compared to dry air. Light in the visible range is more efficient for aerosol scattering experiments. A small number of impurities in the sample will increase its absorbing properties, but, in general, the scattering efficiencies strongly depend on the single-particle mixing state. Smaller particles with a diameter comparable to the wavelength of incident light show higher scattering efficiencies but lower backscattering intensities than larger particles, while surface roughness is shown to strongly alter the polarizability of the particle but has a negligible effect on its single-scattering albedo. Moreover, different shapes have a strong effect on the degree of linear polarization, but, in general, using the spherical over elliptic shape model can underestimate the scattering efficiencies by up to 4%. Finally, variation in the imaginary part of the complex RI can underestimate the single scattering albedo by up to 35.8%.

Sources, transport pathways and radiative effects of BC aerosol during 2018–2020 at a receptor site in the eastern Indo-Gangetic Plain

This study reports black carbon (BC) characteristics and climate effects for a 22-month period during 2018–2020 at a receptor location in the eastern Indo-Gangetic Plains (IGP). The overall averaged BC mass concentration was 7.8 ± 4.7 μg m−3, and the nighttime average (9.1 ± 6.1 μg m−3) was nearly double that of the daytime (5.8 ± 3.5 μg m−3). BC was most enhanced during winter, with mean concentration (14.3 ± 3.8 μg m−3) higher by 4 times as compared to summer. A two-component mixing model, frequency distribution of the Angstrom exponent, and a simultaneous increase in brown carbon (BrC) absorption coefficient suggested that this enhancement was mostly due to the biomass burning (BB) fraction of BC. CALIPSO-derived products showed that the extinction coefficient was highest at 0.62 ± 0.31 km−1 in winter and lowest at 0.12 ± 0.05 km−1 in summer. Backscatter plots and particle depolarization ratios indicated presence of spherical dust particles during summer and smoke plumes during post-monsoon and winter. Concentration-weighted trajectories (CWTs) helped in quantifying significant contributions of the IGP outflow to BC, BC-BB and BrC absorption. Finally, a large direct radiative forcing of the atmosphere by BC (37 ± 22 W m−2) was estimated via the radiative transfer model SBDART, with an associated atmospheric heating rate of 1.02 K d−1.

Spectral Simulation and Error Analysis of Dusty Leaves by Fusing the Hapke Two-Layer Medium Model and the Linear Spectral Mixing Model

The Hapke two-layer medium model is an efficient way of simulating the spectra of dusty leaves. However, the simulation accuracy is low when the amount of dustfall is small. To solve this problem, we introduced the dust coverage factor and the linear spectral mixing model, to improve the accuracy of the Hapke two-layer medium model. Firstly, based on the assumption of spherical dust particles, the arrangement and accumulation mode of the particles were set, and the coverage factor and accumulation thickness of particles in the leaf area were calculated. Then, the coverage factor was used as an abundance. Endmembers were the spectra of dust-free leaves (measured) and dust-covered leaves (simulated by model), and the final simulated spectra were calculated using linear spectral mixing theory. This study presents the following findings: (1) When the coverage factor was calculated using the exponential model, the maximum difference between the corrected simulated spectra and the measured spectra was 3.4%, and the maximum difference between the original simulated spectra and the measured spectra was 15.2%. The accuracy of the corrected spectra is much higher than that of the original simulated spectra. (2) In this study, the physical thickness and optical thickness calculated by the Hapke two-layer medium model are equivalent, which is quite different from the actual dust accumulation. When the linear spectral mixing model is introduced, to modify the simulation value when the number of dust particles accumulated is less than one layer, the spectral endmember value of the simulated dust leaf is replaced by the simulation spectrum when the number of dust particles accumulated is exactly one layer. The calculated cor-rection spectrum has high rationality and credibility. This finding may be beneficial for monitoring amounts of dustfall accurately using remote sensing in mining areas.

3D Active Brownian Motion of Single Dust Particles Induced by a Laser in a DC Glow Discharge.

The active Brownian motion of single dust particles of various types in the 3D electrostatic DC discharge trap under the action of laser radiation is studied experimentally. Spherical dust particles with a homogeneous surface, as well as Janus particles, are used in the experiment. The properties of the active Brownian motion of all types of dust particles are studied. In particular, the 3D analysis of trajectories of microparticles is carried out, well as an analysis of their root mean square displacement. The mean kinetic energy of motion of the dust particle of various types in a 3D trap is determined for different laser powers. Differences in the character of active Brownian motion in electrostatic traps with different spatial dimensions are found.

Determination of the lifting height of dust particles after a mass explosion in an iron ore open pit

Open pit mining is accompanied by emissions of fine dust and hazardous gases into the atmosphere. This is related to the operation of open pit transport, drilling and blasting operations. The release of harmful components into the quarry space and the increase in their concentrations has a negative impact on the health of working personnel and leads to pollution of the environment. In doing so, the nature of fine dust and gases pollution depends on the mining technology and meteorological factors. The problem of reduced effectiveness of dust suppression methods after mass explosions in open pits is relate to insufficient research into the formation of dust and gas cloud. Additional theoretical and experimental research into the dust dynamics of blasting operations is therefore need. The article discusses the stages of formation of the dust and gas cloud after a mass explosion in an iron ore open pit. The results of experimental studies of the evolution of the dust and gas cloud at different points in time after the detonation of borehole charges are presented. Relations for determination of density and dynamic viscosity of gases, gas mixture and gas-dust aerosol are given. A formula for determining the time and height of ascent of spherical dust particles at the dynamic stage of dust and gas cloud formation is obtain. In this case, the assumption is madid that there is no mutual influence of the dynamic and thermal factors after detonation of the charges. The elevation of dust particles due to temperature differences during the heat stage of dust and gas cloud formation is determined. Based on the analysis of the calculation results, the duration of the dynamic stage of cloud formation is determined. It is established that, following the release of solid and gaseous detonation products into the atmosphere, a height distribution of dust particles is observed as a function of their diameter. That said during, the dynamic stage of dust and gas cloud formation, the height of dust particle lift is directly proportional to their diameter, while during the heat stage the inverse relationship is observe. That at the beginning of the thermal stage the deposition of coarse dust particles takes place are established. In this process, fine dust particles rise to a maximum height and are then carried outside the open pit by the airflow.

EmulART: Emulating radiative transfer—a pilot study on autoencoder-based dimensionality reduction for radiative transfer models

Dust is a major component of the interstellar medium. Through scattering, absorption and thermal re-emission, it can profoundly alter astrophysical observations. Models for dust composition and distribution are necessary to better understand and curb their impact on observations. A new approach for serial and computationally inexpensive production of such models is here presented. Traditionally these models are studied with the help of radiative transfer modelling, a critical tool to understand the impact of dust attenuation and reddening on the observed properties of galaxies and active galactic nuclei. Such simulations present, however, an approximately linear computational cost increase with the desired information resolution. Our new efficient model generator proposes a denoising variational autoencoder (or alternatively PCA), for spectral compression, combined with an approximate Bayesian method for spatial inference, to emulate high information radiative transfer models from low information models. For a simple spherical dust shell model with anisotropic illumination, our proposed approach successfully emulates the reference simulation starting from less than 1% of the information. Our emulations of the model at different viewing angles present median residuals below 15% across the spectral dimension and below 48% across spatial and spectral dimensions. EmulART infers estimates for sim 85% of information missing from the input, all within a total running time of around 20 minutes, estimated to be 6times faster than the present target high information resolution simulations, and up to 50times faster when applied to more complicated simulations.

Time fractional model of free convection flow and dusty two‐phase couple stress fluid along vertical plates

AbstractCouple Stress Fluid (CSF) incorporates a new material constant whose, in contrast to a Newtonian fluid, regulates both couple stress and lubricant viscosity. Due to the fourth‐order spatial derivative term that this material constant introduces into the momentum equation, this fluid (CSF), even for classical fluid problems, has received limited research. The aim of this article is to examine the joint impact of heat transmission and magnetic field on a time‐fractional model of two‐phase free convection flow of dusty fluid that is electrically conducting. Among parallel plates, one of which is stationary and the other of which is oscillating with constant velocity, the CSF is supposed to flow. Heat is transferred by free convection and buoyant force, which generates the flow. Furthermore, all spherical dust particles are uniformly dispersed through the fluid. The flow is modeled mathematically in terms of PDEs. The provided derived system of PDEs is generalized by applying a recently invented fractional derivative, the Caputo‐Fabrizio fractional derivative. Finite sine Fourier and Laplace transformations are jointly applied to handle the problem. The velocity and temperature profiles have closed form solutions. The CSF outcomes for stimulating fluid parameters are shown in numerous graphs for CF time fractional derivatives. Additionally, the influence of various parameters has been discussed. Mathcad‐15 is used to plot the graphical outcomes for the CSF, dust particle, and temperature profiles. Furthermore, the skin friction and Nusselt number are calculated. Table 1 demonstrates how the rate of heat transmission reduces as the Peclet number's value rises. Similarly, Table 2 demonstrates that the skin friction increases as the magnetic parameter and couple stress parameter are raised. Table 3 and 4, shows the Regression analysis that the variation in the velocity for Couple stress and dusty fluid parameter are statistically significant. By increasing the couple stress parameter λ, retarde the both velocities profile.

Experimental study on the suppression of coal dust explosion by silica aerogel

Silica aerogel (SiA) is prepared using environmentally friendly material diatomaceous earth and its effect on coal dust explosion is studied. The coal dust explosion characteristics experiments are carried out in a 20 L spherical explosion tank and dust explosion flame propagation experimental system, and the coal dust explosion products are analyzed by FTIR and XPS test methods. The results showed that after adding 50% SiA, the maximum explosion pressure of coal samples decreased from 0.3813 MPa to 0.1854 MPa, (dp/dt)max decreased from 10.955 Mpa/s to 4.082 Mpa/s, weakening by 62.74%, and the flame propagation height decreased from 567.57 mm to almost no flame propagation observed; using the Coats- Redfern method to calculate the activation energy of coal and SiA in the slow reaction stage of 30.353 kJ/mol and 21.159 kJ/mol, indicating that SiA preferentially consumes oxygen in the confined space, slowing down the oxidative pyrolysis of coal; SiA attenuates the impact energy generated by the explosion, protects part of the functional groups of coal from being destroyed, and inhibits the decomposition of some C elements in coal; proposes reduce the thermal radiation effect and decompression deceleration coupling effect to describe the inhibition mechanism of SiA on coal dust explosion.

Spatially resolved mid-infrared observations of the circumstellar environment of the born-again object FG Sge

Context. FG Sge has evolved from the hot central star of the young planetary nebula Hen 1–5 to a G–K supergiant in the last 100 yr. It is one of the three born-again objects that have been identified as of yet, and they are considered to have undergone a thermal pulse in the post-asymptotic giant branch evolution. Aims. We present mid-infrared spectro-interferometric observations of FG Sge and probe its dusty environment. Methods. FG Sge was observed with MIDI at the Very Large Telescope Interferometer at baselines of 43 and 46 m between 8 and 13 µm. Results. The circumstellar dust environment of FG Sge was spatially resolved, and the Gaussian fit to the observed visibilities results in a full width at half maximum of ~10.5 mas. The observed mid-infrared visibilities and the spectral energy distribution can be fairly reproduced by optically thick (τV ≈ 8) spherical dust shell models consisting of amorphous carbon with an inner radius rin of ~30 R★ (corresponding to a dust temperature of 1100 ± 100 K). The dust shell is characterized with a steep density profile proportional to r−3.5±0.5 from the inner radius rin to (5–10) × rin, beyond which it changes to r−2. The dust mass is estimated to be ~ 7 × 10−7 M⊙, which translates into an average total mass-loss rate of ~ 9 × 10−6 M⊙ yr−1 as of 2008 with a gas-to-dust ratio of 200 being adopted. In addition, the 8–13 µm spectrum obtained with MIDI with a field of view of 200 mas does not show a signature of the polycyclic aromatic hydrocarbon (PAH) emission, which is in marked contrast to the spectra taken with the Spitzer Space Telescope six and 20 months before the MIDI observations with wide slit widths of 3″.6–10″. This implies that the PAH emission originates from an extended region of the optically thick dust envelope. Conclusions. The dust envelope of FG Sge is much more compact than that of the other born-again stars’ Sakurai’s object and V605 Aql, which might reflect the difference in the evolutionary status. The PAH emission from the extended region of the optically thick dust envelope likely originates from the material ejected before the central star became H-deficient, and it may be excited by the UV radiation from the central star escaping through gaps among dust clumps and/or the bipolar cavity of a disk-like structure.

Dynamics of spherical charged dust shells in de Sitter space

We study the dynamics of charged, spherically symmetric dust shells in the presence of a positive cosmological constant. We find generalizations of the well-known solutions in asymptotically flat spacetime, in particular orbits into ``parallel universes,'' but also new solutions corresponding to a ``bounce'' of the shell before an event horizon has formed. We also discuss ``bubble'' solutions, in which a charged shell and an oppositely charged singularity are spontaneously created and annihilated.

Strong cosmic censorship conjecture at the dust black hole collapse

The cosmic censorship conjecture proposed by Penrose states that the singularity of a black hole is covered by the event horizon and is not naked. The first examples of violation of this conjecture are from the models of the spherical collapse of the perfect fluid black hole in the dust state. In this article, we examine an important class of LTB spherical dust collapse models in which there is a naked singularity. We will first show that the singularity of a black hole will be spacelike. We then show that the event horizon will be outside the singularity. We will also show that if the energy condition is met, the famous category of these models will not have a naked singularity. We will conclude that the strong cosmic censorship conjecture will be held

Study of generalized Lemaître–Tolman–Bondi spacetime in Palatini f(R) gravity

The objective of this paper is to investigate the continuation of Lemaître–Tolman–Bondi (LTB) space-time for dissipative dust configuration in the direction of Palatini f(R) theory. In this context, the generalized form of field and dynamical equations will be formulated. We explore the effects of kinematical variables and curvature invariant on our proposed fluid configuration. The significance of Palatini f(R) scalar variables computing through the orthogonal splitting of Riemann-tensor for dissipative dust spheres will be reported. Furthermore, two subcases of LTB space-time have been carried out to note down its symmetric aspects. It is revealed that extended LTB space-time has characteristics comparable to that of LTB and computed scalar variables in both situations have identical dependance on source profile even under the effects of Palatini technique.

Modeling of the electrical interaction between desert dust particles and the Earth’s atmosphere

In the current work, the two distinct charging mechanisms of spherical dust particles settling in the Earth’s atmosphere, i.e. ion attachment and contact electrification, are studied in parallel. A novel 1D numerical model has been developed that parametrizes the charging processes in the presence of a large scale electric field, under stagnant atmospheric conditions where wind contribution is neglected. The model is able to self-consistently calculate the modification of atmospheric ion densities and the subsequent alteration of the large scale electric field, when dust particles are present and atmospheric ions attach to them, and is further updated to account for the particle charging due to the efficient collisions between particles of sizes ranging from fine (less than 1μm in radius) to giant mode (larger than 50μm in radius). Due to a lack of a rigorous mathematical expression for the quantification of the particle collision process, the mechanical and electrostatic effects are modeled independently, based on works in the past literature, and then are combined by a simple superposition principle. Additionally, the electrostatic effects are studied in the presence of weak external electric fields (less than 1–2 kV/m). Moreover, for the same reasons a simple superposition principle has been applied for the quantification of the ion attachment process. All these assumptions lead to an approximation of the actual mechanisms quantification, but this method can lead to physically reasonable results, highlighting the impact of several processes to the eventual charging of the dust particles. By binning integration of a realistic particle size distribution in the model, the acquired electrical charge on the dust particles is calculated in the range of 0.5 to 2000 elementary charges. The particles become on average negatively charged, but under specific conditions giant mode particles can be locally and temporarily positive, congruently to previously reported laboratory experiments. Moreover, the electrical force that is applied on the particles by each mechanism individually and through the superposition of both, is extracted and compared to the gravitational force acting on each particle. However, the 1D results indicate that the electrical force is not enough to significantly influence the gravitational settling of the charged particles, as it is more than one order of magnitude less than gravity. This designates that although the electrical processes alone are accounted for, significant meteorological processes such as updrafts, wind shears, or horizontal winds need to be included in the model to accurately represent the modulation of particle electrification and so as to represent the impact of electricity on particle dynamics in a more realistic way.

Opposite Effects of Mineral Dust Nonsphericity and Size on Dust‐Induced Snow Albedo Reduction

AbstractWe quantified the combined effects of mineral dust nonsphericity and size on snow albedo reduction using the MOPSMAP (Modeled optical properties of ensembles of aerosol particles) package and SAMDS (Spectral Albedo Model for Dirty Snow) with the consideration of dust from Sahara, Greenland, San Juan Mountains, and Tibetan Plateau. Results indicate that the dust‐induced albedo reduction decreases by up to 30% as the effective radii of dust particles increase in 1–5 μm. Nonspherical dust enhances snow albedo reduction relative to spherical dust by up to 20%. Stronger enhancements are obtained for higher dust concentration and larger dust size. Furthermore, the dust nonsphericity‐induced enhancement of snow albedo reduction is more pronounced for more‐absorptive dust. Finally, we develop a new parameterization for quantifying the dependence of snow albedo reduction on dust nonsphericity and size, and provide a convenient way for assessing the climate impacts of dust in snow.

Study of cylindrical and spherical dust acoustic solitons and quasiperiodic structures in a quantum dusty plasma

The solitonic and quasiperiodic structures of dust acoustic (DA) waves are investigated in a three components quantum dusty plasma composed of mobile negative dust grains, ions, and inertialess electrons. The reductive perturbation method is employed to derive A deformed Korteweg–de Vries (dKdV) equation in planar and nonplanar geometries, and its numerical solutions are obtained using the two level finite difference approximation method. The influence of geometries on DA solitons is discussed. It is observed that in nonplanar geometries, DA solitons travel at different speeds in comparison to one-dimensional planar ones. Furthermore, in the planar geometry, the bifurcation of DA traveling waves has been analyzed on the framework of the dKdV equation. By adding an external periodic force to the derived dKdV equation, the quasiperiodic behaviors of DA waves are presented.

Calculation model for drag coefficient and multi-phase flow characteristics in dust removal process: Comparison between flake aluminum powder and spherical aluminum powder

It is of great significance to study the force model of flake and spherical particles in a two-phase flow system for reducing dust hazards. In present work, the correspondence between drag coefficient Cd and Re for spherical particle is specified by a new CFD method. Moreover, 144 kinds distribution states for flake particle with equal probability are summarized into 7 kinds stress state models with different occurrence probabilities, and the corresponding relationship between the equivalent drag coefficient Cd and the equivalent Reynolds number Re is further obtained. A series of ventilation and dust removal experiments and full-scale numerical simulation in a large space are carried out, and the maximum error of peak dust concentration between the simulation results and the experimental results for flake powder is 17.4%. In addition, the size effect of flake powder is more obvious than that of spherical powder, and the fluidity of flake powder with equal particle size is obviously better than that of spherical powder, so flake powder can be removed from the production workshop faster. However, in the process of ventilation and dust removal, the diffusion risk of spherical dust larger than 100 μm do not change much during the ventilation process.