Ionized Gas Flow Research Articles

NON-EQUILIBRIUM SUPERSONIC FLOW AROUND A BLUNT

The computational model designed for studying the processes of non-equilibrium physicochemical gas dynamics in supersonic rarefied-air flow past a blunt plate of finite dimensions under the laboratory experiment conditions is formulated. The computational model is based on the two-dimensional Navier–Stokes equations, the energy conservation laws for the translational degrees of freedom of atoms and molecules and the vibrational degrees of freedom of diatomic molecules, and the chemical kinetics and diffusion equations for individual components of partially ionized gas flow. The basic gas dynamic and kinetic processes in flow past a blunt plate are analyzed at the Mach numbers M = 10 and 20. It is shown that regions of thermal nonequilibrium are formed.

Non-Equilibrium Supersonic Flow Past a Blunt Plate at High Angle of Attack

The computational model designed for studying the processes of non-equilibrium physicochemical gas dynamics in supersonic rarefied-air flow past a blunt plate of finite dimensions under the laboratory experiment conditions is formulated. The computational model is based on the two-dimensional Navier–Stokes equations, the energy conservation laws for the translational degrees of freedom of atoms and molecules and the vibrational degrees of freedom of diatomic molecules, and the chemical kinetics and diffusion equations for individual components of partially ionized gas flow. The basic gas dynamic and kinetic processes in flow past a blunt plate are analyzed at the Mach numbers M = 10 and 20. It is shown that regions of thermal nonequilibrium are formed.

On the calculation of the electron temperature flowfield in the DSMC studies of ionized re-entry flows

Currently available procedures of electron temperature calculations in studying ionized flows around reentry spacecraft by the direct simulation Monte Carlo (DSMC) method are analyzed. It is shown that the heat conduction of electrons is not taken into account in these procedures. The contributions of various effects to the electron energy balance are calculated by an example of the RAM-C II capsule, and a numerical solution of the electron energy conservation equation is obtained, which refines the electron temperature distribution used in the DSMC computations. A method of coupled calculation of the electron temperature within the framework of the continuum approach and modelling of ionized gas flow by the DSMC method is proposed.

Study of the ionizing gas flow in the channel of plasma accelerator with different ways of gas inflow at the inlet

Numerical studies of the ionization process are presented for various ways of the gas supplying at the inlet of the coaxial channel of the quasi-stationary plasma accelerator. Simulation of two-dimensional axisymmetric flows of ionizing gas was carried out on the basis of the equations of radiation magnetic gas dynamics taking into account radiation transport. The approximation of local thermodynamic equilibrium in three-component medium consisting of atoms, ions, and electrons was used in the MHD model. It was determined that non-uniform gas inflow at the channel inlet leads to even greater instability of the pulsating unsteady flows of the ionizing gas in the plasma accelerator. The method of long characteristics was used in the 3D model of radiation transport, including the basic mechanisms of emission and absorption for different portions of the spectrum. The radiation field in the ionizing gas flow was determined, including the integral radiation characteristics and the spectral radiation intensities in the narrow ranges of frequencies or photon energies.

Experimental study of high-speed ionized gas flow around plate and wedge model

In the development of magneto-plasma methods for controlling the aerodynamics of promising high-speed aircraft, an important place is occupied by studies of the interaction of ionized gas flows with a shock-wave flow structure. In this work, the flow near a model (a wedge and a plate) by a pulsed stream of air plasma is investigated. As a result of the work, it was shown that a change in the local Mach number in the stream ionized by an electric discharge leads to a change in the shape of the shock wave generated by the leading edge of the model. The temperature of the discharge plasma was estimated, which showed the predominance of the thermal effect on the flow structure.

Radiation transport in ionizing gas flow within the quasi-steady plasma accelerator

Investigation of the radiation transport in the ionizing gas flow in the channel of the quasi-steady plasma accelerator is presented. The model is based on the magnetohydrodynamic (MHD) equations and equation of the radiation transport. In theMHD model the approximation of the local thermodynamic equilibrium was used in the three-component medium consisting of atoms, ions and electrons. The model of the radiation transport includes the basic mechanisms of emission and absorption for different portions of spectrum.

The Second Galactic Center Black Hole? A Possible Detection of Ionized Gas Orbiting around an IMBH Embedded in the Galactic Center IRS13E Complex

Abstract The Galactic Center is the nuclear region of the nearest spiral galaxy, the Milky Way, and contains the supermassive black hole with , Sagittarius A* (Sgr A*). One of the basic questions about the Galactic Center is whether or not Sgr A* is the only “massive” black hole in the region. The IRS13E complex is a very intriguing infrared (IR) object that contains a large dark mass comparable to the mass of an intermediate mass black hole (IMBH) from the proper motions of the main member stars. However, the existence of the IMBH remains controversial. There are some objections to accepting the existence of the IMBH. In this study, we detected ionized gas with a very large velocity width ( km s−1) and a very compact size ( au) in the complex using the Atacama Large Millimeter/submillimeter Array (ALMA). We also found an extended component connecting with the compact ionized gas. The properties suggest that this is an ionized gas flow on the Keplerian orbit with high eccentricity. The enclosed mass is estimated to be by the analysis of the orbit. The mass does not conflict with the upper limit mass of the IMBH around Sgr A*, which is derived by the long-term astrometry with the Very Long Baseline Array (VLBA). In addition, the object probably has an X-ray counterpart. Consequently, a very fascinating possibility is that the detected ionized gas is rotating around an IMBH embedded in the IRS13E complex.

Influence of Ionizing Gas Flow on Structural Homogeneity of Type IV Silica Glass

Type IV silica glass is the key material in inertial navigation and optical field due to its high purity and unbroken structural network. Structural homogeneity of type IV silica glass, which is mainly affected by producing process, is one of the most important properties and determines its usability. The influence of ionizing gas flow of plasma was studied in this paper. Flow rate of working gas and protecting gas was changed and the depositing temperature field was measured. Structural homogeneity of deposited silica glass was discussed by optical homogeneity, fictive temperature and stress birefringence. Results show that more uniform temperature field can be obtained with higher working gas flow and lower protecting gas flow, and the structural homogeneity of type IV silica glass is better. But the proportion of working gas and protecting gas should not be larger than 2. When the working gas and protecting gas are 5 m3/h and 2.5 m3/h respectively, the structural homogeneity of type IV silica glass is the best.

Analysis of the axisymmetrical ionized gas boundary layer adjacent to porous contour of the body of revolution

The ionized gas flow in the boundary layer on bodies of revolution with porous contour is studied in this paper. The gas electroconductivity is assumed to be a function of the longitudinal coordinate x. The problem is solved using Saljnikov's version of the general similarity method. This paper is an extension of Saljnikov?s generalized solutions and their application to a particular case of magnetohydrodynamic (MHD) flow. Generalized boundary layer equations have been numerically solved in a four-parametric localized approximation and characteristics of some physical quantities in the boundary layer has been studied.

IONIZED GAS KINEMATICS AT HIGH RESOLUTION. V. [Ne ii], MULTIPLE CLUSTERS, HIGH EFFICIENCY STAR FORMATION, AND BLUE FLOWS IN HE 2–10

We measured the $12.8\mu$m [NeII] line in the dwarf starburst galaxy He 2-10 with the high-resolution spectrometer TeXeS on the NASA IRTF. The data cube has diffraction-limited spatial resolution $\sim1^{\prime\prime}$ and total velocity resolution including thermal broadening of $\sim5$km/s. This makes it possible to compare the kinematics of individual star-forming clumps and molecular clouds in the three dimensions of space and velocity, and allows us to determine star formation efficiencies. The kinematics of the ionized gas confirm that the starburst contains multiple dense clusters. From the $M/R$ of the clusters and the $\simeq30-40$% star formation efficiencies the clusters are likely to be bound and long lived, like globulars. Non-gravitational features in the line profiles show how the ionized gas flows through the ambient molecular material, as well as a narrow velocity feature which we identify with the interface of the HII region and a cold dense clump. These data offer an unprecedented view of the interaction of embedded HII regions with their environment.

Numerical simulations of turbulent ionized gas flows in the circumsolar protoplanetary disk

An axisymmetric protoplanetary disk model that takes into account the interaction of turbulent gas flows with the magnetic field is considered. A closed system of equations of homogeneous compressible magnetohydrodynamics in the regime of developed turbulence in the gravitational and magnetic fields of a star has been constructed. Apart from the traditional probability-theoretical averaging of the MHD equations, the weighted Favre averaging is used. The approach by A.V. Kolesnichenko and M.Ya. Marov to modeling the turbulent transport coefficients in a weakly ionized disk has been implemented. It allows the inverse effects of the generated magnetic field on a turbulent gas flow and the dissipation of turbulence through kinematic and magnetic viscosities to be taken into account. A parallel code for numerically solving the system of averaged MHD equations has been developed. The averaged gas density and velocity distributions as well as the configuration of the disk’s intrinsic magnetic field at a distance of 1 AU from the star have been obtained through numerical simulations. The assumption that the vertical (parallel to the disk’s rotation axis) magnetic induction component changes much more profoundly in height than in radius and, hence, gives grounds to take into account its gradient in the model of the turbulent kinematic viscosity coefficient has been confirmed.

A fully implicit scheme for simulating ionized gas flows using the gas dynamics electrodynamics coupled system

SUMMARYThe flow of ionized gases under the influence of electromagnetic fields is governed by the coupled system of the compressible flow equations and the Maxwell equations. In this system, coupling of the flow with the electromagnetic field is obtained through nonlinear and stiff source terms, which may cause difficulties with the numerical solution of the coupled system. The discontinuous Galerkin finite element method is used for the numerical solution of this system. For the magnetic field vector, discontinuous Galerkin discretization is performed using a divergence‐free vector base for the magnetic field to preserve zero divergence in the element and retain the implicit constraint of a divergence‐free magnetic field vector down to very low level both globally and locally. To circumvent difficulties resulting from the presence of the stiff source terms, implicit time marching is used for the fully coupled system to avoid wrong wave shapes and propagation speeds that are obtained when the coupling source terms are lagged in time or by using splitting iterative schemes. Numerical solutions for benchmark problems computed on collocated meshes for the flow and electromagnetic field variables with this fully coupled monolithic approach showed good agreement with other numerical solutions and exact results. Copyright © 2014 John Wiley & Sons, Ltd.

Radiation-pressure-driven dust waves inside bursting interstellar bubbles

Massive stars drive the evolution of the interstellar medium through their radiative and mechanical energy input. After their birth, they form bubbles of hot gas surrounded by a dense shell. Traditionally, the formation of bubbles is explained through the input of a powerful stellar wind, even though direct evidence supporting this scenario is lacking. Here we explore the possibility that interstellar bubbles seen by the Spitzer- and Herschel space telescopes, blown by stars with log(L/L_sun) < 5.2, form and expand due to the thermal pressure accompanying ionization of the surrounding gas. We show that density gradients in the natal cloud or a puncture in the swept up shell lead to an ionized gas flow through the bubble into the general interstellar medium, which is traced by a dust wave near the star, demonstrating the importance of radiation pressure during this phase. Dust waves provide a natural explanation for the presence of dust inside H II bubbles, offer a novel method to study dust in H II regions and provide direct evidence that bubbles are relieving their pressure into the ISM through a champagne flow, acting as a probe of the radiative interaction of a massive star with its surroundings. We create a parameter space connecting the ambient density, the ionizing source luminosity, and the position of the dust wave, while using the well-studied H II bubbles RCW 120 and RCW 82 as benchmarks of our model. Finally, we briefly examine the implications of our study for the environments of super star clusters formed in UltraLuminous InfraRed Galaxies (ULIRGs), merging galaxies and the early Universe, which occur in very luminous and dense environments and where radiation pressure is expected to dominate the dynamical evolution.

Analysis of the planar boundary layer of ionized gas adjacent to porous contour

Planar ionized gas (air) flow in the boundary layer under the conditions of the socalled equilibrium ionization is studied in this paper. The contour of the body within the fluid is porous. The ionized gas flows through the magnetic field of the power Bm =Bm(x)˙It is assumed that the ionized gas electro-conductivity is a function of the ratio of the longitudinal velocity and the velocity at the outer edge of the boundary layer. Using the general similarity method, the governing boundary layer equations are brought to a generalized form, and as such solved numerically. Some conclusions concerning behavior of the boundary layer physical quantities and characteristics of compressible fluid flow have been drawn.

Autowaves in a dc complex plasma confined behind a de Laval nozzle

Experiments to explore stability conditions and topology of a dense microparticle cloud supported against gravity by a gas flow were carried out. By using a nozzle-shaped glass insert within the glass tube of a dc discharge plasma chamber a weakly ionized gas flow through a de Laval nozzle was produced. The experiments were performed using neon gas at a pressure of 100 Pa and melamine-formaldehyde particles with a diameter of 3.43 μm. The capturing and stable global confining of the particles behind the nozzle in the plasma were demonstrated. The particles inside the cloud behaved as a single convection cell inhomogeneously structured along the nozzle axis in a tube-like manner. The pulsed acceleration localized in the very head of the cloud mediated by collective plasma-particle interactions and the resulting wave pattern were studied in detail.

On the ionized gas boundary layer adjacent to the bodies of revolution in the case of variable electroconductivity

This paper studies the ionized gas i.e. air flow in an axisymmetrical boundary layer adjacent to the bodies of revolution. The contour of the body within the fluid is nonporous. The ionized gas flows under the conditions of equilibrium ionization. A concrete form of the electroconductivity variation law has been assumed and studied here. Through transformation of variables and introduction of sets of parameters, V. N. Saljnikov's version of the general similarity method has been successfully applied. Generalized equations of axisymmetrical ionized gas boundary layer have been obtained and then numerically solved in a three-parametric localized approximation.

Magnetogasdynamic flow and heat transfer in a microchannel with isothermally heated walls

The presence of ionized gas flow in an applied electric and magnetic field could result in an electromagnetic driving force and a joule heating. It is desirable to understand the causes of the two mechanisms and their roles on ionized gas microflow and heat transfer. In this study, a mathematical model is developed of the pressure-driven gas flow through a long isothermally heated horizontal planar microchannel under an applied electric and magnetic field. The fully developed solutions of the flow and thermal field distributions as well as the corresponding characteristics are derived analytically and presented in terms of dimensionless parameters. It is found that an electromagnetic driving force can be produced by a combined non-zero electric field and negative magnetic field and results in an additional velocity slip and an additional flow drag. Also, a joule heating can be produced only by an electric field and enhanced by a positive magnetic field and results in an additional temperature jump and an additional heat transfer. The effects of electromagnetic driving force and joule heating on velocity slip and temperature jump can be magnified by increasing the Knudsen number; however, the force and heating effects on flow drag and heat transfer rate are found to be diminished.

Energy and force prediction for a nanosecond pulsed dielectric barrier discharge actuator

A three-species physical model is presented for dielectric barrier discharge (DBD) actuator under atmospheric pressure. The governing equations are solved for temporal and spatial distribution of electric potential and charge species using the finite element based multiscale ionized gas flow code. The plasma model is loosely coupled with compressible Navier-Stokes equations through momentum and energy source terms. Two cases of rf powered and nanosecond pulsed barrier discharge actuators are simulated. Based on the imparted time average electrohydrodynamic force and power deposition to the neutral gas, the nanosecond pulsed DBD actuator creates significant pressure variations within few microseconds. These results are in reasonable agreement with recently reported experimental shadow images.

A brightz= 5.2 lensed submillimeter galaxy in the field of Abell 773

During our Herschel Lensing Survey (HLS) of massive galaxy clusters, we have discovered an exceptionally bright source behind the z = 0.22 cluster Abell 773, which appears to be a strongly lensed submillimeter galaxy (SMG) at z = 5.2429. This source is unusual compared to most other lensed sources discovered by Herschel so far, because of its higher submm flux (~200 mJy at 500 μm) and its high redshift. The dominant lens is a foreground z = 0.63 galaxy, not the cluster itself. The source has a far-infrared (FIR) luminosity of LFIR = 1.1 × 1014/μ L⊙, where μ is the magnification factor, likely ~11. We report here the redshift identification through CO lines with the IRAM-30 m, and the analysis of the gas excitation, based on CO(7–6), CO(6–5), CO(5–4) detected at IRAM and the CO(2–1) at the EVLA. All lines decompose into a wide and strong red component, and a narrower and weaker blue component, 540 km s-1 apart. Assuming the ultraluminous galaxy (ULIRG) CO-to-H2 conversion ratio, the H2 mass is 5.8 × 1011/μ M⊙, of which one third is in a cool component. From the C I(3P2-3P1) line we derive a C I/H2 number abundance of 6 × 10-5 similar to that in other ULIRGs. The H2Op(2,0,2−1,1,1) line is strong only in the red velocity component, with an intensity ratio I(H2O)/I(CO) ~ 0.5, suggesting a strong local FIR radiation field, possibly from an active nucleus (AGN) component. We detect the [NII]205 μm line for the first time at high-z. It shows comparable blue and red components, with a strikingly broad blue one, suggesting strong ionized gas flows.

Shadow method for measuring the electron density in a barrier discharge plasma on the Zhukovskii airfoil surface

We have measured the electron temperature and density distributions in an ionized gas flow initiated by a high-frequency barrier discharge on the Zhukovskii airfoil surface by the method of photometry of shadow patterns for two probe radiation wavelength λr = 0.675 μm and λb = 0.425 μm. The investigation was carried out in air at atmospheric pressure. The maximum value of the electron density was N e ∼ 2.2⋅1015 cm−3 with an insignificant change in the air temperature in the discharge gap.