Dust Velocity Research Articles

Maximum dust-to-gas mass flux ratio in spherically expanding dusty-gas flow

In this paper, we consider the motion of a solid spherical particle in a spherically expanding gas flow as an elementary model of the gas-dust atmosphere of a comet. Based on the results of numerical simulations we propose an approximation for the terminal dust velocity and an estimate of the maximum dust-to-gas mass flux ratio (in a dusty-gas flow with the dust size distribution given by a power law) which is consistent with assumption of negligible impact of dust on the gas flow (frequently used in simulations of dusty gas flows).

The effect of dust on the propagation of a hydromagnetic solitary wave along the magnetic field in a cold collision-free plasma

The effect of dust is studied on the parallel propagation of a solitary hydromagnetic wave in a magnetized, cold, collision-free plasma. The fully nonlinear analysis is based on the Adlam–Allen method. The system of nonlinear differential equations was derived using the assumption of massive dust, namely, that the dust velocity is constant and parallel to the background magnetic field. Self-consistent solutions obtained from the model for the lighter particles dynamics and for the resulting electric and magnetic fields are presented, together with the validity range of Mach numbers as a function of dust parameters. In particular, supersonic solutions are possible in scenarios tending to two-component plasmas (positively charged ions and negatively charged dust). The stationary solitary pulse in terms of particle densities, magnitude of transverse magnetic field, transverse electron–ion velocities, and bipolar electric field is presented. The magnitude of these amplitudes is maximum at the center of wave and minimum at the boundary. Furthermore, it is shown that all the solitary wave amplitudes are decreases with dust parameter.

Direct Measurements of Dust Settling Velocity Under Low‐Density Atmospheres Using Time‐Resolved Particle Image Velocimetry

AbstractDust dynamics influence planetary atmospheres. However, the settling velocity of dust—and thus its residence time in the atmosphere—is often mispredicted. Challenging, indirect experiments involving few ideal particles revealed that dust settling velocity deviates from Stokes' law under rarefied atmospheres. While useful, such experiments are inadequate to simulate more complex scenarios, including variable particles sizes and shapes. Here, we present direct measurements of settling velocity for spherical particles under Earth‐to‐Mars atmospheric pressures using time‐resolved particle image velocimetry (TR‐PIV), and validate their robustness with existing models. Our results demonstrate that TR‐PIV provides a relatively simple approach to quantifying dust settling velocity from direct observations of over 10,000 particles, enabling systematic investigations of dust settling under realistic scenarios. Such experiments will have significant implications for our understanding of Mars' past, present, and future ‐ from providing a tool to decipher its sedimentary record to enhancing predictive capabilities of atmospheric models.

Investigation into the ignition sensitivity and detonation kinetics of Al/RDX energetic dust

Given the prevalence of Al/RDX energetic dust in industrial production, this study investigates their ignition safety and explosion hazards using Hartmann tubes and 20 L spherical explosion containers. The minimum ignition energy (MIE) increases from 20 mJ to 55 mJ as RDX content increases, indicating that adding RDX enlarges the effective particle size of the dust, thereby reducing its ignition sensitivity. A logistic regression model was used to develop a fitting equation for ignition probability, correlating dust concentration and ignition energy. The flame propagation velocity and explosion pressure of the energetic dust initially increase and then decrease with increasing RDX content. Optimal combustion characteristics were observed at 20 % RDX, with the maximum flame propagation velocity of 101 m s−1. However, the peak flame temperature decreases with increasing RDX content. The maximum explosion pressure and maximum explosion index at 1.77 MPa and 186.99 MPa m s−1 respectively, at 40 % RDX content. These findings highlight that 20 % RDX content yields the best combustion characteristics, while 40 % RDX content offers the maximum explosive potential, providing valuable insights for enhancing safety measures in industrial applications involving energetic dusts.

Imaging-based measurement of lunar dust velocity and particle size.

This paper introduces an optical-mechanical system designed for the dynamic detection and analysis of lunar dust, typically characterized as particles under 20micrometers on the lunar surface. The system's design is both compact and lightweight, aligning with the payload constraints of lunar exploration missions. It is capable of real-time tracking and recording the motion of lunar dust at various altitudes, a crucial capability for understanding the environmental dynamics of the lunar surface. By capturing images and applying sophisticated algorithms, the system accurately measures the velocity and size of dust particles. This approach significantly advances the quantitative analysis of lunar dust, especially during agitation events, filling a critical gap in our current understanding of lunar surface phenomena. The insights gained from this study are not only pivotal for developing theoretical models of lunar surface air flow disturbances and dust movement but also instrumental in designing effective dust mitigation and hazard avoidance strategies for future lunar missions, thereby enhancing both scientific knowledge and the engineering applications in lunar exploration.

Electrostatic Dust Analyzer for Dust Transport Measurements on the Lunar Surface

Lunar dust charging and transport is a more than five-decade-old problem. A high-fidelity and flight-qualified Electrostatic Dust Analyzer (EDA) has been developed to measure the charge, velocity, mass (size), and flux of electrostatically lofted dust particles on the lunar surface. Recent laboratory findings have greatly advanced our fundamental understanding of the dust-charging and -lofting mechanisms, providing critical constraints to the design of the EDA instrument. EDA consists of two identical dust trajectory sensor (DTS) units on both ends of the instrument with a deflection field electrode (DFE) unit lying in between. When a dust particle enters the instrument, charge signals induced on four arrays of wire electrodes in the two DTS units determine the total charge of the dust particle and its trajectory passing through the instrument from which the dust velocity vector is measured. The mass (size) is derived from the deflection of the dust trajectory by the DFE. A dust campaign was performed to characterize the instrument’s performance. The results meet or exceed the requirements. EDA has achieved high Technology Readiness Level 6. EDA measurements are important for assessing the dust environment on the lunar surface and its subsequent impact on crew safety and the operation of exploration systems. Additionally, EDA measurements are expected to have important implications for the surface evolution of all airless bodies, including the Moon and asteroids, in the solar system.

Analytic description of the gas flow around planets embedded in protoplanetary disks

Context. A growing planet embedded in a protoplanetary disk induces three-dimensional gas flow, which exhibits a midplane outflow that can suppress dust accretion onto the planet and form global dust substructures (rings and gaps). Aims. Because analytic formulae for the planet-induced outflow are useful for modeling its influences on local and global dust surface densities and planet accretion, we derived analytic formulae that describe the morphology and velocity of the planet-induced outflow. Methods. We first performed three-dimensional, nonisothermal hydrodynamical simulations of the gas flow past a planet, which enabled us to introduce a fitting formula that describes the morphology of the outflow. We then derived an analytic formula for the outflow speed using Bernoulli’s theorem. Results. We successfully derived a fitting formula for the midplane outflow morphology (the shape of the streamline), which is valid when the dimensionless thermal mass falls below m ≲ 0.6. The obtained analytic formulae for the outflow, such as the maximum outflow speed and the velocity distributions of the outflow in the radial and vertical directions to the disk, show good agreement with the numerical results. We find the following trends: (1) the maximum outflow speed increases with the planetary mass and has a peak of ~30–40% of the sound speed when the dimensionless thermal mass is m ~ 0.3, corresponding to a super-Earth mass planet at 1 au for the typical steady accretion disk model, and (2) the presence of the headwind (namely, the global pressure force acting in the positive radial direction of the disk) enhances (reduces) the outflow toward the outside (inside) of the planetary orbit. Conclusions. The planet-induced outflow of the gas affects the dust motion when the dimensionless stopping time of dust falls below St ≲ min(10 m2, 0.1), which can be used to model the dust velocity influenced by the outflow.

An exact solution for unsteady three-dimensional magnetohydrodynamic Casson flow of dusty nanofluid over a porous stretching sheet

The unsteady three-dimensional (3D) Casson flow of a nanofluid containing dust particles over a porous, linearly stretching sheet in the presence of an external magnetic field is studied. It is assumed that the sheet is stretched in both directions along the xy plane. The governing equations of the two-phase model are partial differential equations that are transformed into ordinary equations using similarity transforms. The nanofluid is a suspension of water-based nanoparticles. In this study, we look at how nanoparticle size affect the properties of dusty nanofluid flow. The mathematical model contains the basic equations for the fluid and dust phases in the form of three-dimensional partial differential equations, which are transformed into dimensionless ordinary-dimensional equations using an appropriate similarity transformation. An exact analytical solution to this boundary value problem is obtained. The effects of various physical values on dust and nanofluid velocities are discussed in detail, including the Casson parameter, magnetic parameter, porosity parameter, fluid-particle interaction parameter, mass concentration of dust particles, and nanoparticle size. In a few specific instances, the current analytical solution demonstrates a good agreement with previously published numerical investigations.

Microscopic deposition-property relationships in microbial-induced consolidation of coal dusts

In recent years, the preparation of new microbial dust suppressants based on microbial induced carbonate precipitation (MICP) technology through enriched urease-producing microbial communities has become a new topic in the field of coal dust control. The deposition of CaCO3 was the key to suppress coal dust. However, deposition characteristics in the field is not sufficient and the relationship between deposition characteristics and erosion resistance is not clear, which hinders the development of engineering application of new microbial dust suppressant. Therefore, based on X-CT technology, this paper observed and quantified micro-deposition of bio-consolidated coal dust with different calcium sources. Furthermore, a conceptual framework for deposition was proposed and its correlation with erosion resistance was revealed. The results showed that CaCO3 induced by calcium chloride and calcium lactate was aggregate deposited. Aggregate deposited CaCO3 was small in volume, showed the distribution of aggregation in the central area and loose outside, and mosaiced pores. CaCO3 induced by calcium nitrate was surface deposition due to attached biomass. Surface deposition was mostly large volume CaCO3 expanding from the inside out, which could cover coal dust to a high degree and completely cemented pores. In addition, the threshold detachment velocity of coal dust cemented by surface deposition was increased by 17.6–19.1% compared to aggregate deposition. This depended on the abundance and strength of CaCO3 bonding between coal dust particles under different deposition. The two-factor model based on porosity and CaCO3 coverage can well express relationship between erosion resistance and depositional characteristics. Those results will help the engineering application of MICP technology in coal dust suppression.

Predictive atmospheric dispersion and deposition characteristics of activated tungsten dust

Tungsten is considered to be the most promising material for plasma-facing components of fusion reactors in addition to other industrial and military uses. Activated tungsten dust produced by plasma-wall interaction and released under accidental conditions would be the emerging environmental pollutant with both chemical and radiation toxicity. For the first time, atmospheric dispersion and deposition characteristics were investigated for tungsten dust with various particle size spectrum similar as generated in fusion reactors. Euler-Lagrange approach was adopted to describe parcels motion and deposition behaviors. Proper numbers of parcels were determined for the atmospheric dispersion and various parcel diameters scale. Near-surface concentration distribution and dry deposition velocity were predicted for tungsten dust with both single size dust and realistic particle size spectrum dust. Influences of chemical forms and release factors on atmospheric dispersion and deposition of tungsten dust were preliminary identified at last. It is indicated that 150 million parcels are needed for 10 μm dust under 5 km scale. Dry deposition velocity of tungsten dust is up to 11.3 cm s−1 and increase along with particle diameter because of its high density and gravitational deposition effect. The critical diameter judging whether gravitational deposition could appear for tungsten dust is 1 µm. Deposited particle size spectrum would be completely different along the downwind distance which would result in differences in subsequent behaviors in other environmental compartments.

Experimental investigation on the explosion characteristics and flame propagation behavior of aluminum hydride dust

Aluminum hydride (AlH3) dust is a high-capacity hydrogen storage material but is prone to explosion. In this paper, explosion characteristics and flame propagation behavior of AlH3 dust are investigated. The results indicate that the exposure of bare aluminum and the increase of specific surface area lead to the maximum explosion pressure of AlH3 dust being 4 times higher than that of Al dust. The enhancement of heat transfer by hydrogen combustion causes a higher combustion rate, leading to a higher maximum explosion pressure rise rate and flame propagation velocity of AlH3 dust. The thermo-diffusive instabilities and the evolution of hydrogen result in a pulsation flame propagation velocity of AlH3 dust. Combining the explosion temperature calculated by NASA CEA with the explosion residues analysis, the explosion mechanism of AlH3 dust is further revealed. The break of the oxide film and the combustion of hydrogen result in a different explosion mechanism.

A comparative investigation of the explosion mechanism of metal hydride AlH3 dust and Al/H2 mixture

Aluminum hydride (AlH3) is an excellent hydrogen storage material, whereas hydrogen is easily released because of the low-temperature dehydrogenation characteristic. Therefore, the explosion mechanism of AlH3 dust is explored by comparison with the Al/H2 mixture. The findings indicate that since the residual aluminum after hydrogen evolution combusts more completely, AlH3 has a higher explosion pressure value than Al/H2 mixture. However, the explosion pressure rise rate and average flame propagation velocity of AlH3 dust are lower than those of Al/H2 mixture. It is attributed to the initial free hydrogen state and initial higher hydrogen concentration of Al/H2 mixture. The key radicals that generate main explosion residues Al2O3 are AlO and O. AlH3(+M) ≤> AlH + H2(+M) has the greatest sensitivity on the formation of O and AlO. Hydrogen combustion expedites the phase transition process of aluminum dust, while their competition for oxygen is not conducive to the formation of Al2O3.

Effectiveness of melting phenomenon in two phase dusty carbon nanotubes (Nanomaterials) flow of Eyring-Powell fluid: Heat transfer analysis

Present research explores the thermal outcomes of Eyring Powell material with decomposition of dusty particles. The heat transfer observations are assessed with carbon nanotubes. The single walled carbon nanotubes (SWCNs) are used to improve the thermal exploration of Eyring Powell dusty material. The problem is further studied with implementation of magnetic force. The expressions of dust particles and Eyring Powell nonlinear model are used to construct the mathematical model. The simulations are justified numerically with shooting method. The graphical impact of parameters is tested. The results show that both phase and dust velocity profile increases for interaction velocity constant and Eyring fluid parameter. The lower variation in phase fluid temperature profile is claimed temperature interaction constant.

Ice, Ice, Maybe? Investigating 46P/Wirtanen’s Inner Coma for Icy Grains

The release of volatiles from comets is usually from direct sublimation of ices on the nucleus, but for very or hyperactive comets other sources have to be considered to account for the total production rates. In this work, we present new near-IR (NIR) imaging and spectroscopic observations of 46P/Wirtanen taken during its close approach to Earth on 2018 December 19 with the MMIRS instrument at the MMT Observatory to search for signatures of icy or ice-rich grains in its inner coma that might explain its previously reported excess water production. The morphology of the images does not suggest any change in grain properties within the field of view, and the NIR spectra do not show the characteristic absorption features of water ice. Using a new Markov Chain Monte Carlo–based implementation of the spectral modeling approach of Protopapa et al., we estimate the areal water ice fraction of the coma to be <0.6%. When combined with slit-corrected Af ρ values for the J, H, and K bands and previously measured dust velocities for this comet, we estimate an icy grain production rate of less than 4.6 kg s−1. This places a strict constraint on the water production rate from pure icy grains in the coma, and in turn we find that for the 2018–2019 apparition approximately 64% of 46P’s surface was actively sublimating water near perihelion. We then discuss 46P’s modern properties within the context of other (formerly) hyperactive comets to understand how these complex objects evolve.

Impact of turbulence intensity and fragmentation velocity on dust particle size evolution and non-ideal magnetohydrodynamics effects

ABSTRACT We investigate the influence of dust particle size evolution on non-ideal magnetohydrodynamic (MHD) effects during the collapsing phase of star-forming cores, taking both the turbulence intensity in the collapsing cloud core and the fragmentation velocity of dust particles as parameters. When the turbulence intensity is small, the dust particles do not grow significantly, and the non-ideal MHD effects work efficiently in high-density regions. The dust particles rapidly grow in a strongly turbulent environment, while the efficiency of non-ideal MHD effects in such an environment depends on the fragmentation velocity of the dust particles. When the fragmentation velocity is small, turbulence promotes coagulation growth and collisional fragmentation of dust particles, producing small dust particles. In this case, the adsorption of charged particles on the dust particle surfaces becomes efficient and the abundance of charged particles decreases, making non-ideal MHD effects effective at high densities. On the other hand, when the fragmentation velocity is high, dust particles are less likely to fragment, even if the turbulence is strong. In this case, the production of small dust particles becomes inefficient and non-ideal MHD effects become less effective. We also investigate the effect of the dust composition on the star and disc formation processes. We constrain the turbulence intensity of a collapsing core and the fragmentation velocity of dust for circumstellar disc formation due to the dissipation of the magnetic field.

Study on the dust migration law and a spray dust suppression scheme in transportation roadway

To solve the problem of excessive dust concentration in the belt transportation roadway of the mine. Numerical simulations were used to study the dust migration in the belt transportation roadway under 1.5m/s ventilation conditions. The simulation results show the process of dust ejection from the inflow chute to contamination of the whole belt transportation roadway, and the spatial distribution of dust velocity. A comprehensive dust reduction scheme of "central suppression and bilateral splitting" was designed according to the dust distribution, with simultaneous control of the infeed chute and the roadway. In practical application, pneumatic spraying greatly reduces the amount of dust in the guide chute. The misting screen has a significant effect on dust collection and segregation. The solution effectively controls the dust in the space of 20m on both sides of the transfer point, and the dust removal efficiency reaches more than 90%.

Study on the preparation of novel FR-245/MCM-41 suppressant and its inhibition mechanism on oil shale deflagration flame

Oil shale development is of great significance because oil and gas resources are scarce. Research on the prevention of oil shale dust explosion is particularly important for guaranteeing the safe development and utilization of oil shale resources. In this work, the flame morphology and velocity of oil shale dust with and without MCM-41 or FR-245 were compared. Furthermore, the novel green FR-245/MCM-41 inhibitor was prepared by jet mill method and used in oil shale dust explosion for the first time. The best ratio of FR-245/MCM-41 for flame inhibition was obtained, which was 9: 1. The pyrolysis oxidation behavior of oil shale before and after adding FR-245/MCM-41 was analyzed and compared by FWO and KAS methods, respectively. The results showed that the activation energy calculated by FWO and KAS methods greatly increased after adding FR-245/MCM-41, which increased by 95.36% and 115.15% than that before adding inhibitor, respectively. Significantly, the activation energy is particularly high for two methods when α between 0.2 and 0.6, due to that MCM-41 and FR-245 coexisted to limit the oxidation of oil shale. For α between 0.7 and 0.9, the activation energy is still high because of the existence of MCM-41. Combining the oil dust flame propagation behavior with the characterization results before and after explosion, the physical-chemical synergy mechanism of oil dust flame propagation inhibition was revealed.

Molecular dynamics simulation and modelling on the dust-wall interactions in tokamak

Dust velocity in fusion devices covers a wide range (several hundreds of m/s to over 10 km/s), which can cause various interactions between energetic dust grains and wall materials. Dust grain with low energy can influence the wall properties by deposition. Intense dust-wall interactions can cause serious wall damage such as sputtering, degradation, deformation and so on. As beryllium and tungsten are the material of the first wall and divertor, respectively, systematically molecular dynamics simulations have been performed to study the interactions between beryllium/tungsten dust and the beryllium/tungsten wall in the present study. A wide range of dust velocity has been considered to cover the velocity from experiments. Our result shows that the influences of dust on the wall are greatly affected by the impact velocity of dust grains and the properties of the wall material. A detailed analysis shows that the dust-wall interaction can be divided into four levels and an analytical model has been developed to explain the mechanism. Character velocities that separate the interaction levels are also provided by the model. The comparison between the MD result and the model shows a good agreement. Our result is helpful for the understanding of the mechanisms and the prediction of dust-wall interactions.

An exact solution of a Casson fluid flow induced by dust particles with hybrid nanofluid over a stretching sheet subject to Lorentz forces

The concept of a hybrid nanofluid has piqued the interest of numerous researchers due to its potential for increased thermal properties, which results in high transfer rates. Hybrid nanofluids are used in heat transport systems such as electronic cooling, and applications in biomedical and pharmaceutical relief. Thus, the present paper inspects the impact of Lorentz forces on the Casson fluid flow of water-based Fe3O4-MWCNT hybrid nanofluid induced by dust particles from a stretching sheet. The leading PDEs are changed into ODEs by employing similarity variables and then achieving an exact solution for these transformed ODEs. The impacts of distinct physical constraints including fluid interaction particle parameter, Casson parameter, and magnetic parameter on the dust velocity and fluid velocity for normal nanofluid (Fe3O4/H2O) and hybrid nanofluid (Fe3O4-MWCNT/ H2O) are addressed in detail. The present analytic solution shows a strong correlation with earlier published numerical studies in limited cases.

Experimental study on the minimum ignition energy of cornstarch particle-air flows in a horizontal pipeline

Pipelines and process equipment are commonly interconnected in a network of dust extraction or pneumatic conveying in lines industry. History has shown that the severity of a dust deflagration could be much accentuated if the initial fireball is allowed to propagate further through pipelines. However, less is known about the hazard of a primary ignition in a pipeline conveying system with combustible dust and high airflow velocity. This paper presents an experimental study on the ignitability of cornstarch particle-air flow in a lab-scale piping system. The results show that minimum ignition energy (MIE) of dried cornstarch flow at 12–28 m/s was less than 300 mJ, and the minimum explosible concentration (MEC) was less than 100 g/m3. An increase in airflow velocity increased both MIE and MEC, as well as stretching the spark plasma. Moisture in the dust significantly decreased its ignitability, with this being a more marked factor than airflow velocity in influencing the ignition hazard in a pipeline.