Compressive Dust Research Articles

Propagation of higher-order compressive dust–ion acoustic solitary waves in a dusty plasma with weak relativistic electrons

Propagation of higher-order compressive dust–ion acoustic solitary waves in a dusty plasma with weak relativistic electrons

Kelvin-Helmholtz instability in a compressible dust fluid flow

We report the first experimental observations of a single-mode Kelvin-Helmholtz instability in a flowing dusty plasma in which the flow is compressible in nature. The experiments are performed in an inverted Pi-shaped dusty plasma experimental device in a DC glow discharge Argon plasma environment. A gas pulse valve is installed in the experimental chamber to initiate directional motion to a particular dust layer. The shear generated at the interface of the moving and stationary layers leads to the excitation of the Kelvin-Helmholtz instability giving rise to a vortex structure at the interface. The growth rate of the instability is seen to decrease with an increase in the gas flow velocity in the valve and the concomitant increase in the compressibility of the dust flow. The shear velocity is further increased by making the stationary layer to flow in an opposite direction. The magnitude of the vorticity is seen to become stronger while the vortex becomes smaller with such an increase of the shear velocity. A molecular dynamics simulation provides good theoretical support to the experimental findings.

The Compressive and Rarefactive Dust Acoustic Solitary Waves with Two Different Temperatures for Both Electrons and Ions

The Compressive and Rarefactive Dust Acoustic Solitary Waves with Two Different Temperatures for Both Electrons and Ions

Cubic nonlinearity driven dust ion acoustic solitons with superthermal two-temperature electrons in the Saturn’s magnetosphere

Nonlinear propagation of electrostatic waves with cubic nonlinearity has been investigated in a multicomponent dusty plasma with inertial ions, superthermal two temperature electrons and stationary dust. In this regard, single and multi-soliton solutions of modified Korteweg–de Vries (mKdV) equation for dust ion acoustic waves (DIAWs) have been investigated implementing Hirota’s bilinear method. Plasma parameters affecting the amplitude of dust ion acoustic (DIA) mKdV single soliton have been thoroughly investigated based on the data from Saturn’s magnetosphere. The overtaking interaction of two mKdV solitons has been investigated by changing the percentage of propagation vectors to observe bipolar structure reducing to a single humped structure for a particular value of the ratio of propagation vectors. The most significant outcome of this study has been the investigation of interaction of a compressive and rarefactive dust ion acoustic soliton forming a peculiar composite shape at the interaction point.

Physical and Mechanical Properties of Eco-Friendly Composites Made from Wood Dust and Recycled Polystyrene

The development of alternative wood composites based on the use of waste or recycled materials can be beneficial due to over exploitation of natural resources. Under this frame, an option for the successful utilization of waste polystyrene which avoids environmental problems that formaldehyde adhesives cause and also reduces waste disposal, is its potential application as a binder for the production of value-added environmentally friendly and low cost wood composites. Two types of panel were successfully made, consisting of wood dust and two recycled polystyrene contents, namely, 15% and 30%. Both physical properties, water absorption and thickness swelling, and mechanical properties, modulus of rupture, shear strength parallel in the plane of the board and glue line shear strength, were significantly improved as the recycled polystyrene content increased from 15% to 30%. Water absorption and thickness swelling after 24 h immersion in water were improved by 165% and 750% as the recycled polystyrene content increased from 15% to 30%. The magnitude of the improvement in mechanical properties however, was less pronounced than of the physical properties since modulus of rupture, shear strength parallel in the plane of the board and glue line shear strength were increased by 43.6%, 50% and 61.5%, respectively. The low viscosity of the recycled polystyrene caused more mobility inside the panel matrix and therefore, an improved penetration took place into adequate depth of the compressed dust particles. It is concluded that boards can be successfully produced using these waste raw materials, wood dust and recycled polystyrene in organic solvent as a binder, and therefore it can reduce waste disposal and provide cleaner production for the development of wood-based boards.

The tensile strength of compressed dust samples and the catastrophic disruption threshold of pre-planetary matter

ABSTRACT During the planetary formation process, mutual collisions among planetesimals take place, impacting on their porosities. The outcome of these collisions depends, among other parameters, on the tensile strength of the colliding objects. In the first stage of this work, we performed impact experiments into dust samples, assembled with material analogous to that of the primitive Solar System, to obtain highly compressed samples that represent the porosities measured in chondritic meteorites. In the second stage, we obtained the tensile strengths of the compressed dust samples by the Brazilian Disc Test. We found a correlation between the tensile strength and the volume filling factor of the compressed dust samples and obtained the corresponding critical fragmentation strength in mutual collisions and its dependence on the volume filling factor. Finally, we give prescriptions for the catastrophic disruption threshold as a function of the object size, for different values of the volume filling factor.

Thermal conductivity and coordination number of compressed dust aggregates

Understanding the heat transfer mechanism within dust aggregates is of great importance for many subjects in planetary science. We calculated the coordination number and the thermal conductivity through the solid network of compressed dust aggregates. We found a simple relationship between the coordination number and the filling factor and revealed that the thermal conductivity through the solid network of aggregates is represented by a power-law function of the filling factor and the coordination number.

Effect of ion nonthermality on nonlinear dust acoustic wave propagation in a complex plasma in presence of secondary electron emission

In this paper we have investigated the effect of ion nonthermality on nonlinear dust acoustic wave propagation in a complex plasma in presence of secondary electron emission considering equilibrium dust charge positive. In space and astrophysical plasmas presence of nonthermal ions have been detected by satellite observations. This ion nonthermality modifies propagation characteristics of dust acoustic waves when dust grains are charged by secondary electron emission mechanism. In case of dust charging by secondary electron emission process two stable equilibrium dust charge states exist out of which one is negative and the other is positive. Here we have considered positive equilibrium dust charge state and both adiabatic and nonadiabatic dust charge variation. Our investigation shows that characteristics of both dust acoustic soliton and dust acoustic shock depend on the strength of the ion nonthermality along with secondary electron yield. Increase in both ion nonthermality and secondary electron yield help to retain the shape of compressive dust acoustic soliton when dust charge variation is adiabatic and to maintain oscillation of the dust acoustic shock when dust charge variation is nonadiabatic.

Effect of secondary electron emission on nonlinear dust acoustic wave propagation in a complex plasma with positive equilibrium dust charge

In this paper, we have investigated the effect of secondary electron emission on nonlinear propagation of dust acoustic waves in a complex plasma considering equilibrium dust charge positive and compared the results with those obtained in our recently published paper [Bhakta et al., Phys. Plasmas 24, 023704 (2017)] where the equilibrium dust charge was negative. In both papers, primary and secondary electrons are assumed to follow Boltzmann distribution with separate electron temperatures, ions are also Boltzmann distributed, and charged dust grains are inertial. Change in the nature of dust charge (negative to positive) gives rise to some opposite behaviour of wave propagation characteristics in dusty plasma when dust grains are charged by secondary electron emission mechanism. Both adiabatic and nonadiabatic dust charge variations have been separately considered in both the papers. The investigation in this paper shows that compressive dust acoustic soliton propagates in case of adiabatic dust charge variation whose amplitude increases and width decreases with an increase in the strength of the secondary electron emission. This is in contrast to the case of negative equilibrium dust charge which confirms the existence of rarefied dust acoustic soliton with decreasing amplitude and increasing width for an increase in the strength of the secondary electron emission. Nonadiabaticity of dust charge variation in both cases generates dust acoustic shock wave which is oscillatory for weak nonadiabaticity and monotonic for strong nonadiabaticity. For positive equilibrium dust charge, the amplitude of both oscillatory and monotonic shocks increases and oscillation of the oscillatory shock persists longer for stronger secondary electron emission. On the other hand for negative equilibrium dust charge, the amplitude of both the oscillatory and monotonic shocks diminishes with increasing secondary electron emission.

Effect of Non-Uniform Coal Dust Distribution in a Gaseous-Dusty Premixed Environment on Flame Acceleration due to Wall Friction

While a premixed flame front would consume an unburnt matter with a constant speed SL, such a flame occurs extremely seldom in the reality, where flames are curved and characterized by another velocity, Sw, and it is oftentimes conventionally assumed that the ratio Sw/SL is proportional to the corrugated flame surface area scaled by the planar one. However, the thermal-chemical parameter SL may experience spatial and temporal variations; in particular, due to the combustible (coal) dust impurities. The present study initiates a systematic investigation of the influence of local variations of the thermal-chemical flame properties on the global flame dynamics. This particular work focuses on the effects of SL-variations on flame acceleration due to wall friction in a gaseous-dusty premixture. Specifically, we performed the computational simulations of the reacting flow equations, with compressible hydrodynamics and combustible coal dust particles incorporated into the original (gaseous) computational platform by replacing an “effective fluid” with the locally-modified, dust-induced flow and flame parameters. Keeping in mind a coalmine passage, we employed a channel with a large aspect ratio. Various spatial distributions of the coal dust concentration are studied, namely: homogenous, linear, cubic and parabolic. As a result, the similarity and differences in the evolutions of the flame shape and velocity have been identified for each distribution. It is shown that the non-uniform distributions may result in an extra distortion or a local stabilization of the flame front, which promotes or reduces the flame surface area, thereby facilitating or moderating flame acceleration due to wall friction.

Electrostatic compressive and rarefactive dust ion-acoustic solitons in four component quantum plasma

Electrostatic compressive and rarefactive dust ion-acoustic solitons in four component quantum plasma

PIC simulation of compressive and rarefactive dust ion-acoustic solitary waves

The nonlinear propagations of dust ion-acoustic solitary waves in a collisionless four-component unmagnetized dusty plasma system containing nonextensive electrons, inertial negative ions, Maxwellian positive ions, and negatively charged static dust grains have been investigated by the particle-in-cell method. By comparing the simulation results with those obtained from the traditional reductive perturbation method, it is observed that the rarefactive KdV solitons propagate stably at a low amplitude, and when the amplitude is increased, the prime wave form evolves and then gradually breaks into several small amplitude solitary waves near the tail of soliton structure. The compressive KdV solitons propagate unstably and oscillation arises near the tail of soliton structure. The finite amplitude rarefactive and compressive Gardner solitons seem to propagate stably.

Predictive scenario for methane- air-dust fires in a mining passage: Effect of compressibility and non- homogeneous dust distributions.

Accidental gas/dust explosions constitute a tremendous hazard for personnel and equipment in industries, such as coal mining industry that has one of the highest occupational fatality and injury rates, claiming hundreds of lives annually. Among various factors driving fires in coal mines, such as turbulence, acoustics, wall friction and obstacles; combustion instabilities, dust impurities and a finger shape of the flamefront play the dominant role. Focusing on these acceleration mechanisms, a predictive scenario of a methane-air- dust fire in a mining passage is developed, and the characteristic stages of the flame evolution are identified. Starting with gaseous fuels, the formulation is then extended to dusty- gaseous medium, with combustible and inert dust as well as their mixture employed. Specifically, the effects of equivalence ratio as well as dust size and concentration on the flame evolution are systematically investigated. While initial formulations are assumed to be incompressible and distribution of gas-dust particles is homogeneous, later, formulations are separately extended to compressible and non-homogenous dust distribution scenarios.Acknowledgements: The authors would like to thank the National Science Foundation for funding this work (NSF CAREER Award #1554254).

Interlaboratory comparison on 137Cs activity concentration in fume dust

Abstract A comparison was conducted, between 11 European National Metrology Institutes and EC-JRC, on measurement of 137Cs activity concentration in fume dust. As test material an activity standard produced from real contaminated fume dust was used. The standard material consisted of 13 cylindrical samples of compressed fume dust. The material contained 137Cs and 60Co of reference activity concentrations of (9.72±0.10) Bq/g and (0.450±0.018) Bq/g, respectively, for the reference date of 1 June 2013, determined using the comparison results. The organization and results of the intercomparison, as well as the process of obtaining reliable reference values are presented.

Compressive and rarefactive dust ion-acoustic solitary waves with degenerate electron–positron–ion plasma

The nonlinear propagation of dust ion-acoustic (DIA) waves in a unmagnetized collisionless degenerate dense plasma (containing degenerate electron and positron, and classical ion fluids) has been theoretically investigated. The K-dV equation has been derived by employing the reductive perturbation method and by taking into account the effect of different plasma parameters in plasma fluid. The stationary solitary wave solution of K-dV equation is obtained, and numerically analyzed to identify the basic properties of DIA solitary structures. It has been shown that depending on plasma parametric values, the degenerate plasma under consideration supports compressive or rarefactive solitary structures. It has been also found that the effect of pressures on electrons, ions, and positrons significantly modify the basic features of solitary waves that are found to exist in such a plasma system. The relevance of our results in astrophysical objects such as white dwarfs and neutron stars, which are of scientific interest, is discussed briefly.

An investigation of the relationship between compressive strength and dust generation potential of magnetite pellets

Iron ore pellets should have sufficient mechanical strengths against degradation at all stages of pellet production in pelletizing plants. Besides the strength, pellets should have less dust emission during operation since the process efficiency and the pelletizing equipments are adversely affected by dust. Dust is also a problem for sintered (product) pellets since they abrade during transportation from pellet production site to the reduction facilities. Sufficient mechanical strength and low dust emission of pellets are necessary for better operation and handling of pellets. In this study, dust emission mechanism of sintered magnetite pellets produced with different binders was comparatively studied. The results showed that the dust is not produced by pellet breakdown for sintered pellets with sufficient strength. It was found that dust generation of sintered pellets is not directly dependent on the mechanical strength. One of the dust generation mechanisms of sintered pellets with sufficient strength is the roughness of pellet surfaces. The attrition and impact forces during transportation cause dust generation from pellet surfaces. The surface smoothness is more important since the pellets with high strength and rough surfaces produced more dust than those with smooth surfaces and low strength. Half of the fines generated due to pellet attrition or impact forces during handling of sintered pellets will become airborne and are considered as loss and operational/environmental problem. The percentage of particulate matter (PM10) which is significant in health risk lied between 30% and 40% by weight of airborne pellet dust.

Kelvin–Helmholtz instability in a weakly coupled dust fluid

We present a non-local linear stability analysis of the shear flow driven Kelvin–Helmholtz (KH) instability in a weakly coupled dusty plasma fluid with particular emphasis on modifications arising from compressibility and dispersive effects. Unlike a neutral hydrodynamic fluid, the effect of compressibility in a dusty plasma originates from finite dust temperature as well as from the finite temperatures of electron and ion fluids which couple to the dust fluid through Coulomb interactions and this feature leads to a much stronger variability of the compressibility effect. Likewise, unlike a neutral fluid, a weakly coupled dust fluid supports compressible dust acoustic perturbations which are dispersive in nature. Our work investigates these issues in detail by carrying out analytical studies for simple forms of shear profiles and exact numerical evaluations for complex shear flows. A perturbative analytic treatment is also presented to elucidate the role of weak compressibility on the KH mode. The nonlinear regime of the instability has also been studied by evolving the equations governing the dynamics of the dusty plasma system. The nonlinear code is first validated against the linear results for the KH mode. Observations on the saturation of the instability in the nonlinear regime and the development of flow patterns during the course of evolution are presented. A comparison of the compressible case with the incompressible case has been provided.

Robotize Kinematics Modeling on the Loading Mechanism of Back-Loaded Compressed Dust Cart

The three-dimensional geometric kinematics model of the loading mechanism of back-loaded compressed dust cart is established based on the robot kinematics principle and Denavit-Hartenberg（D-H） method. In this paper, the loading mechanism's principle is discussed and it’s institutions simplified robotize model is established, coordinate transformation process and gesture of the skateboard and scraper of the loading mechanism have been studied in the D-H coordinate, has certain significance for improving the product design methods and the manufacturing quality.

Dust acoustic solitary waves in non-thermal plasmas consisting of negatively charged dust grains and isothermal electrons

AbstractA Korteweg–de Vries (KdV) equation is derived here, that describes the nonlinear behaviour of long-wavelength weakly nonlinear dust acoustic waves propagating in an arbitrary direction in a plasma consisting of static negatively charged dust grains, non-thermal ions and isothermal electrons. It is found that the rarefactive or compressive nature of the dust acoustic solitary wave solution of the KdV equation does not depend on the dust temperature if σdc < 0 or σdc > σd*, where σdc is a function of β1, α and μ only, and σd*(<1) is the upper limit (upper bound) of σd. This β1 is the non-thermal parameter associated with the non-thermal velocity distribution of ions, α is the ratio of the average temperature of the non-thermal ions to that of the isothermal electrons, μ is the ratio of the unperturbed number density of isothermal electrons to that of the non-thermal ions, Zdσd is the ratio of the average temperature of the dust particles to that of the ions and Zd is the number of electrons residing on the dust grain surface. The KdV equation describes the rarefactive or the compressive dust acoustic solitary waves according to whether σdc < 0 or σdc > σd*. When 0 ≤ σdc ≤ σd*, the KdV equation describes the rarefactive or the compressive dust acoustic solitary waves according to whether σd > σdc or σd < σdc. If σd takes the value σdc with 0 ≤ σdc ≤ σd*, the coefficient of the nonlinear term of the KdV equation vanishes and, for this case, the nonlinear evolution equation of the dust acoustic waves is derived, which is a modified KdV (MKdV) equation. A theoretical investigation of the nature (rarefactive or compressive) of the dust acoustic solitary wave solutions of the evolution equations (KdV and MKdV) is presented with respect to the non-thermal parameter β1. For any given values of α and μ, it is found that the value of σdc completely defines the nature of the dust acoustic solitary waves except for a small portion of the entire range of the non-thermal parameter β1.

Formation of large-amplitude dust ion-acoustic shocks in dusty plasmas

Theoretical and numerical studies of self-steepening and shock formation of large-amplitude dust ion-acoustic waves in dusty plasmas are presented. A comparison is made between the nondispersive two fluid model, which predicts the formation of large-amplitude compressive and rarefactive dust ion-acoustic shocks, Vlasov simulations, and recent laboratory experiments.