Consider the unsteady incompressible dusty gas to be confined in the space y >0 and the flow is produced by the motion of the finite flat plate moving with the velocity ϑe −λ 2 t in x direction. The gas has small electrical conductivity and the electromagnetic force produced is also very small. According to Saffman (1962) the equation of motion of the dust gas and the dust particles along x−axis are given by
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Abstract: This paper concerns the propagation of shock waves in an enclosure filled with dusty gas. The main motivation for this problem is to probe the effect on such dynamics of solid particles dispersed in the fluid medium. This subject, which has attracted so much attention over recent years given its important implications in the study of the structural stability of systems exposed to high- energy internal detonations, is approached here in the framework of a hybrid numerical two-way coupled Eulerian-Lagrangian methodology. In particular, insights are sought by considering a relatively simple archetypal setting corresponding to a shock wave originating from a small spherical region initialized on the basis of available analytic solutions. The response of the system is explored numerically with respect to several parameters, including the blast intensity (via the related value of the initial shock Mach number), the solid mass fraction (mass load), and the particle size (Stokes number). Results are presented in terms of pressure-load diagrams. Beyond practical applications, it is shown that a kaleidoscope of fascinating patterns is produced by the “triadic” relationships among multiple shock reflections events and particle-fluid and particle-wall interaction dynamics. These would be of great interest to researchers and scientists interested in fundamental problems relating to the general theory of pattern formation in complex nonlinear multiphase systems.
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In a companion paper we have shown how the equations describing gas and dust as two fluids coupled by a drag term can be re-formulated to describe the system as a single-fluid mixture. Here, we present a numerical implementation of the one-fluid dusty gas algorithm using smoothed particle hydrodynamics (SPH). The algorithm preserves the conservation properties of the SPH formalism. In particular, the total gas and dust mass, momentum, angular momentum and energy are all exactly conserved. Shock viscosity and conductivity terms are generalized to handle the two-phase mixture accordingly. The algorithm is benchmarked against a comprehensive suit of problems: DUSTYBOX , DUSTYWAVE , DUSTYSHOCK and DUSTYOSCILL ,
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were not related to SPH but inherent to the two-fluid formalism. First, if dust particles concentrate below the resolution length of the gas phase, they tend to become trapped there, since they no longer feel any differential forces from the gas (see Ayliffe et al. 2012 for a discussion of this issue in SPH simulations; and Price & Fed- errath 2010 for the same issue in a grid-based context). Secondly, when handling the specific problem of strong drag regimes (cor- responding to small grains), we found two limitations which lead to a prohibitive computational cost: (1) the drastically small time steps required for the numerical stability of explicit schemes or the complexity of the implicit schemes involved, and less trivially (2) a high spatial resolution required to resolve the differential velocity between the gas and the dust in order to simulate the correct physi- cal dissipation rate. The latter occurs because even if the differential velocity between the fluids is damped after a few stopping times t s ,
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equilibrium is frequently limited by gas transport through the porous adsorbant. Additional examples are found in cases of non-catalytic gas/solid reactions where the solid reactant or product is a porous solid and the reactant and product gases must be transported into and out of this solid. Fre quently, such reactions as ,for example ,the reduction of iron oxide, the roasting of the sulphide ores, etc involves the formation of solid product layers on the outside of the original solid particles. Gas diffusion is also important in other technical fields such as vapour penetration into foundry sands, outgassing of powder metal compacts, drying e t c .
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Very recently, Gangwar  has studied theoretically the effect of overtaking disturbances on adiabatic propagation of cylindrical strong shock waves in mixture of small spherical inert dust particles and a real gas having power varying initial density distribution. He found that the consideration of flow behind the shock has a significant effect on the flow variables of shock propagation. The aim of the present study is to investigate the motion of cylindrical imploding shock in a real dusty gas having uniform initial density distribution by using CCW (Chester-Chisnell-Whitham) method, The effect of overtaking disturbances (EOD) on the freely propagation of shock is included using a technique developed by Yadav. The strength of overtaking waves is estimated under the assumption that both C + and C - disturbances propagate in the medium of same density distribution. It is assumed
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Rao et al.  have studied dust acoustic (DA) waves propagating linearly as a normal mode and non- linearly as supersonic solitons of either positive or negative electrostatic potentials in a dusty plasma with inertial charged dusts and Boltzmann distributed electrons and ions. In the study of non-linear dust acoustic waves  in unmagnetized dusty plasma with the effects of vortex-like and non thermal ion distributions, large amplitude rarefactive as well as compressive solitons are reported to exist. In a similar approach with sufficient non thermality in the ions following Cairn’s distribution  , and sufficient negative charges on the dust along with electrons, Verheest and Pillay  have investigated the existence of both positive and negative solitary structures in some parameter space. Besides taking some non thermal parameter in the thermal distribution of ions as variable, DA solitary waves  are studied in dusty plasmas with the help of pseudo-potential method. The existence of rarefactive solitons in magnetized non thermal dusty electronegative plasma is also reported  in which width is shown to decrease at the increase of 𝐵 0 , whereas amplitude is shown to remain unaffected.
Yazd is one of arid areas in Iran and constantly prone to floating dust particles in the air. This is important regarding environmental issues and human health. In this paper a day when due to the amount of dust particles visibility reduces to 5,000 m is considered the dusty day. In this research dusty days and wind speed of 4 synoptic stations were studied during 2008-2010.wind speed and directions were correlated with dust occurance. Table (1) indicates that 16 days of 22 selected days of study have experienced dustystorms. This shows a significant correlation between wind speed and direction. Almost in all cases this significance is up to 99% confidence level. It means that there is a direct relation between wind speed and wind direction, getting more nearer to 360° (north), wind speed increases, so severe winds blow from north.
Nowadays, dusty, both in space and under laboratory conditions are the object of numerous investigations [1-6]. Besides traditional investigation of dusty plasmas in connected with it influence to communication, flights of airplanes and people living near volcano and another eruptions. There are also the artificial dust clouds in the atmosphere caused by industrial pollutions, very danger for communication and for flights. An attractive property of dusty plasmas is supporting various oscillations and waves, both linear and nonlinear [2,3,7-11]. There are a lot of papers devoted to the waves in bounded or inho- mogeneous plasmas, where some types of surface plasma waves can exist and the presence of the dust component can affect essentially their characteristics [5-12]. A dis- tinctive property of the dust component is a possibility to get plasmas with dust particles of various properties in different parts of the system [1-3,5]. For instance, it is
This paper presents the study of stagnation point of hydromagnetic flow of dusty fluid over a stretching sheet with the bottom surface of sheet heated by convection from hot fluid. The governing partial differential equations are transformed into a system of nonlinear ordinary differential equations using similarity transformation. These resulting nonlinear ordinary differential equations are solved numerically by using Runge-Kutta Fehlberg fourth-fifth order method (RKF45 Method). The characteristics of velocity and temperature profiles of hydromagnetic fluid flow of dusty fluid are analyzed and discussed for different parameters of interest such as convective Biot number, fluid-particle interaction parameter, magnetic parameter, ratio of free stream velocity parameter and Prandtl number on the flow. The numerical results are compared with previous published results for validation.
Some polluted white dwarfs are dynamically active and they vary on short timescales. For example, the infrared ﬂ ux of SDSS J0959 − 0200 dropped by 35% between two observations in 2010 and then remained at the same level until at least 2014 ( Xu & Jura 2014 ) . The gas emission lines around WD J1617 + 1620 disappeared within a few years ( Wilson et al. 2014 ) . Most gas disks show gradual variations over a few years ( Wilson et al. 2015; Manser et al. 2016a, 2016b; Red ﬁ eld et al. 2017; Dennihy et al. 2018 ) . Recently, transits from an actively disintegrating asteroid were detected around WD 1145 + 017 ( Vanderburg et al. 2015 )— a white dwarf that is also heavily polluted, has an infrared excess from a dust disk, and displays absorption lines from circumstellar gas ( Xu et al. 2016 ) . The optical light curve of WD 1145 + 017 is changing on a daily basis, likely due to the vigorous nature of tidal disruption ( e.g., Gänsicke et al. 2016; Gary et al. 2017 ) .
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This work aims to quantify the effect of solid contaminants getting into the lubricant from the polluted and dusty ambient. The cement factory is a case study in this work as the environment in such factories is extremely polluted and dusty because of the cement manufacturing plant. The raw materials for cement (sand clay, iron ore and lime stone), are the main reason for dust. Additionally, this work aims to determine the most suitable lubricant additives that can reduce the contamination effects on wear rates of mechanical parts. This work was limited according to the time loose to carry out the experiment.
Abstract :- The present paper deals with the study of an unsteady laminar flow of an electrically conducting dusty visco-elastic fluid between oscillating plates in presence of an uniform magnetic field. The flow is due to the influence of pulsatile pressure gradient, oscillations of plates, and the presence of an uniform magnetic field. The flow analysis is carried out in Frenet frame field system. The solutions of the problem are obtained in two different cases by applying Laplace transform technique. Skin-friction at the boundaries in each cases are also calculated. Further, graphs are drawn for different values of Hartmann number, number density of the dust particles, and time.
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The amplitudes of subsonic compressive and rarefactive DA solitons are found to be increased [Fig-2] when the direction of propagation is nearly in the perpendicular direction to the magnetic field. Otherwise in the magnetised dusty plasma, high amplitude subsonic compressive and rarefactice solitons are dependent on the direction of propagation and small Z d . The characteristic behaviour of the magnitude of soliton
There are other equipment used to assess the skidding property and the texture of a pavement. From a survey carried out by the Land Transport Safety of New Zealand, test methods used by 29 authorities for assessing the skidding property are SCRIM 35%, British Pendulum Tester 29%, Grip Tester 16% and Mu-Meter 3%. However, it appears that not much consideration have been made to assess the effect of fine loose particles on the pavement under dry condition. Skid property would be critical during the wet day with the present of thin film of water but, sand and dust would be detrimental in dry condition. It is necessary to provide a possible assessment on a dry dusty surface.
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Star formation (SF) history holds the key to understand- ing galaxy evolution, and—from a wider perspective—the nature of our Universe. One of the obstacles to observing starburst regions in galaxies using optical telescopes is dust. On the other hand, protostars form from dust clouds and molecular gas. Most of the dust in galaxies is quite cool ( ∼ 10–20 K), and its emission is visible only in the far in- frared (Glass, 1999). A warm dust component might be observable during starburst activity (Phillips, 2005). The newly born, blue massive stars are surrounded by gas and dust, which obscure the most interesting regions and, ad- ditionally, absorb a part of the ultraviolet (UV) light emit- ted by stars. Dust heated in this way re-emits the absorbed light in the infrared wavelengths, mostly in the far infrared. Even very careful observations in the UV and optical ranges of wavelengths cannot provide a detailed description of the SF processes in galaxies. The infrared (IR) emission, re- ﬂecting the dust-obscured SF activity of galaxies (Genzel and Cesarsky, 2000), combined together with UV and op- tical data, can give full information about the star forma- tion history and rate. Additionally, the ratio between the UV and far infrared (FIR) emission may serve as an indi-
Various modes of propagation in a dusty plasma arise from the fact that frequencies associated with dust particles are smaller than those for electrons and ions. These waves are ultra-low frequency dust modes (Rao, 1996) and are associ- ated with the dust particle inertia. Here, charged dust grains have a collective behavior and take part in the wave dynam- ics. As examples of these oscillation modes, we could men- tion dust acoustic waves (DAW) (Rao et al., 1990; D’Angelo, 1995) and electrostatic dust-cyclotron waves (EDCW) (Sora- sio and Rosenberg, 2001). Magnetized dusty plasmas support additional electrostatic low-frequency waves involving the dynamics of magnetized/unmagnetized dust grains and mag- netized electrons/ions, i.e., dust lower hybrid (DLH) waves with ω ω ci , which propagate nearly perpendicular to the
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On the other hand, the modelling of K-band Keck interferometric observations tracing the continuum and gas in the inner region of the disc results in an inclination angle of 75 ◦ (Eisner, Hillenbrand & Stone 2014, table 6) for an emitting region within a fraction of 1 au. This is a significantly higher inclination and closer to edge-on than for the outer disc. We note that some of the Keck interferometer data for RW Aur A was taken during the first eclipse in 2010/2011. The discrepancy in the inclinations between inner and outer disc may be evidence for a large-scale warp in the disc, possibly caused by interaction with the companion RW Aur B. Thus, RW Aur B may have an effect on the disc, but it is unlikely to be the direct cause of the feature that eclipses RW Aur A.
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Another important factor that came to our knowledge after carrying out this survey was that almost 60% of people having allergies are allergic to dust and dust particles, which is quite a large percentage of the total population. This maybe due to the fact that is an increased amount of dust in our surroundings whether it be from the wind, old furniture, frequent construction of roads and buildings or other such factors which are aggravating dust allergies amongst the population. This factor if not taken into serious consideration may result in the development of asthma. Hence if the government or building companies are not taking into consideration the health of their people we ourselves must practice self care and increase the use of masks when in a dusty surrounding.Concluding our results and survey we pray that we all work together to build a stable, healthy and safe environment for ourselves.
Figure 7. Left: SFE versus IR luminosities following the same symbols and colours shown in the left-hand panel of Fig. 5. Blue solid line is the best-fitting parametrization considering all the galaxy samples at z < 0.4 presented in the figure (see equation 7) while the light grey area is the region within a 1σ scatter of 0.5 dex. This parametrization suggests a break on the star formation efficiency at L IR = 10 11 − 12 L . Right: Molecular gas fraction (f M H2 ) versus redshift for different samples of SFGs. The upside down triangles are the average values from COLDGASS survey. The dashed and solid blue curves are the average behaviour for normal galaxies and the expected location for starburst galaxies by Bauermeister et al. (2013), respectively. The light grey area is the region of the ‘main-sequence’ for SFGs when adopting an average τ M H2 (MS) ∼ 2.2 Gyr (e.g. Bigiel et al. 2008; Leroy et al. 2008). The two black curves show semi-analytic prescriptions for galaxy formation by Lagos et al. (2011), which correspond to mass halo models of M h = 10 11 and 10 12 M h − 1 , from thinnest
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