Symmetry

Editorial

Jump to: Research, Review

3 pages, 179 KiB

Open AccessEditorial

Plasma and Thermal Physics

by Sergei V. Ryzhkov

Symmetry 2023, 15(6), 1180; https://doi.org/10.3390/sym15061180 - 1 Jun 2023

Viewed by 1030

Abstract

Symmetrically designed fusion and heat concepts, space propulsion, and energy conversion issues with a particular interest in kinetic analysis, plasma power balance, advanced fuels, and alternative systems as new trends in experiments and theory, in physics, power engineering, and in very specific related [...] Read more.

Symmetrically designed fusion and heat concepts, space propulsion, and energy conversion issues with a particular interest in kinetic analysis, plasma power balance, advanced fuels, and alternative systems as new trends in experiments and theory, in physics, power engineering, and in very specific related areas such as space processes, cosmology, and turbulence are very important in fundamental and applied science from an engineering physics perspective [...] Full article

(This article belongs to the Special Issue Plasma and Thermal Physics)

Research

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9 pages, 1403 KiB

Open AccessArticle

Effect of Symmetry/Asymmetry of Shear Rotation of a Plasma Column in a Radial Electric Field on the Level of Turbulent Density Fluctuations

by Dmitry N. Karbushev and Alexei Yu. Chirkov

Symmetry 2023, 15(4), 909; https://doi.org/10.3390/sym15040909 - 13 Apr 2023

Cited by 1 | Viewed by 1095

Abstract

The influence of the properties of the profile of a radial static electric field E(r) on the evolution of an unstable ion temperature–gradient (ITG) drift wave in a nonuniformly rotating plasma column in a magnetic field is studied. The effect [...] Read more.

The influence of the properties of the profile of a radial static electric field E(r) on the evolution of an unstable ion temperature–gradient (ITG) drift wave in a nonuniformly rotating plasma column in a magnetic field is studied. The effect of symmetry on the decrease in the level of turbulent fluctuations, which are associated with the limiting state of the ITG wave during its destruction, is discussed. The level of turbulence is estimated in the framework of approximation of finite amplitudes depending on the electric field structure. It is shown that the maximum decrease in the level of fluctuations occurs with a symmetrical configuration of the radial electric field. Full article

(This article belongs to the Special Issue Plasma and Thermal Physics)

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12 pages, 369 KiB

Open AccessFeature PaperArticle

On the Polarization Dependence of Two-Photon Processes including X-ray Scattering

by Nikolai L. Manakov and Alexei V. Meremianin

Symmetry 2023, 15(2), 422; https://doi.org/10.3390/sym15020422 - 5 Feb 2023

Cited by 1 | Viewed by 1365

Abstract

The polarization dependence of the cross sections of two-photon transitions including X-ray scattering was analyzed. We developed the regular approach to the derivation of the polarization parameters of photoprocesses. Our approach is based on the tensor representation of the photon density matrix, which [...] Read more.

The polarization dependence of the cross sections of two-photon transitions including X-ray scattering was analyzed. We developed the regular approach to the derivation of the polarization parameters of photoprocesses. Our approach is based on the tensor representation of the photon density matrix, which is written in terms of the unit vectors directed along the major axis of the polarization ellipse (

\hat{ϵ}

) and the photon propagation (

\hat{k}

). Explicit expressions for the product of two photon density matrices were derived. As an example, the parametrization of the polarization dependence of the X-ray scattering by closed-shell atoms is given both in terms of (i) scalar products of photon vectors

{\hat{ϵ}}_{1, 2}

,

{\hat{k}}_{1, 2}

and (ii) X-ray Stokes parameters. We discuss the applicability of the atomic scattering for the measurement of the polarization of X-rays. Full article

(This article belongs to the Special Issue Plasma and Thermal Physics)

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12 pages, 1326 KiB

Open AccessArticle

Ab Initio Calculations of Transport and Optical Properties of Dense Zr Plasma Near Melting

by Vladimir Fokin, Dmitry Minakov and Pavel Levashov

Symmetry 2023, 15(1), 48; https://doi.org/10.3390/sym15010048 - 24 Dec 2022

Cited by 5 | Viewed by 1621

Abstract

The dynamic electrical conductivity of dense Zr plasma near melting is calculated using ab initio molecular dynamics and the Kubo–Greenwood formula. The antisymmetrization of the electronic wave function is considered with the determinant of one-electron wave functions; exchange and correlation effects are treated [...] Read more.

The dynamic electrical conductivity of dense Zr plasma near melting is calculated using ab initio molecular dynamics and the Kubo–Greenwood formula. The antisymmetrization of the electronic wave function is considered with the determinant of one-electron wave functions; exchange and correlation effects are treated via an exchange–correlation functional. Optical properties are restored using the Kramers–Kronig transformation. The influence of computational parameters and inner shell electrons on the results is thoroughly investigated. We demonstrate the convergence of our computations and analyze comparison with experimental data. Full article

(This article belongs to the Special Issue Plasma and Thermal Physics)

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11 pages, 1733 KiB

Open AccessArticle

Modification of Vibrational Parameters of a D_∞h-Symmetric Triatomic Molecule in a Laser Plasma

by Aleksei S. Kornev, Vladislav E. Chernov, Petr Kubelík and Martin Ferus

Symmetry 2022, 14(11), 2382; https://doi.org/10.3390/sym14112382 - 11 Nov 2022

Cited by 3 | Viewed by 1451

Abstract

We estimate theoretically the strong-field-modified vibrational parameters of three-atomic

A B A

molecules with

D_{\infty h}

symmetry in a laser-induced plasma. The linear CO

_{2}

and CS

_{2}

molecules in the

X^{1} Σ_{g}

state are considered as examples. We show [...] Read more.

We estimate theoretically the strong-field-modified vibrational parameters of three-atomic

A B A

molecules with

D_{\infty h}

symmetry in a laser-induced plasma. The linear CO

_{2}

and CS

_{2}

molecules in the

X^{1} Σ_{g}

state are considered as examples. We show that double degeneracy of the

Π_{u}

mode is removed due to reduction of the

A B A

molecule symmetry by the laser field. The linear form of

A B A

molecule is preserved, the bond length being elongated. Full article

(This article belongs to the Special Issue Plasma and Thermal Physics)

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14 pages, 2566 KiB

Open AccessArticle

Probe Diagnostics and Optical Emission Spectroscopy of Wave Plasma Source Exhaust

by Andrei I. Shumeiko, Viktor D. Telekh and Sergei V. Ryzhkov

Symmetry 2022, 14(10), 1983; https://doi.org/10.3390/sym14101983 - 22 Sep 2022

Cited by 13 | Viewed by 1747

Abstract

Wave plasma sources (WPSs) were first proposed in the 1970s for electric propulsion (EP), and these research and development processes culminated in the flight test in 2021 of the WPS-based thruster REGULUS. Recently, new approaches to WPS use have emerged—multiple schemes of EPs [...] Read more.

Wave plasma sources (WPSs) were first proposed in the 1970s for electric propulsion (EP), and these research and development processes culminated in the flight test in 2021 of the WPS-based thruster REGULUS. Recently, new approaches to WPS use have emerged—multiple schemes of EPs that can generate propelling forces in multiple directions within a single thruster head, regarded as a breakthrough technology for in-space propulsion systems (PSs). One of the concepts is the bi-directional wave plasma thruster that is based on the open-ended gas discharge chamber—the symmetrical system. Up to now, the WPSs based on the open-ended chambers have not been widely studied. In this paper, the plasma flow formed by the WPS based on the open-ended chamber was axially characterized using a retarding potential analyzer (RPA), Langmuir probe (LP), and optical emission spectroscopy (OES). The presence of the double-layer (DL) was confirmed by a drastic change in the plasma potential along the axis, and a specific impulse of 1100 s was indirectly measured. The measurement results show the potential of the WPS based on the open-ended chamber for efficient operations. Full article

(This article belongs to the Special Issue Plasma and Thermal Physics)

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14 pages, 1223 KiB

Open AccessEditor’s ChoiceArticle

The Qualitative and Quantitative Study of Radiation Sources with a Model Configuration of the Electrode System

by Victor V. Kuzenov and Sergei V. Ryzhkov

Symmetry 2021, 13(6), 927; https://doi.org/10.3390/sym13060927 - 23 May 2021

Cited by 34 | Viewed by 3108

Abstract

This research is devoted to the calculation and theoretical analysis of physical processes in the powerful electric discharge sources of UV radiation and shock waves with required and controlled technical and physical characteristics. Based on the calculations, the processes of converting the initially [...] Read more.

This research is devoted to the calculation and theoretical analysis of physical processes in the powerful electric discharge sources of UV radiation and shock waves with required and controlled technical and physical characteristics. Based on the calculations, the processes of converting the initially stored electromagnetic energy into internal, kinetic, magnetic and radiation energy formed in the electro-discharge plasma sources of plasma formation were studied, and the interactions of discharged plasma and its radiation with matter in different aggregate states were also studied. All the main magneto-plasma dynamic and radiative parameters of plasma formation in the electric discharge sources of UV radiation and shock waves are obtained. Full article

(This article belongs to the Special Issue Plasma and Thermal Physics)

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22 pages, 1133 KiB

Open AccessArticle

Numerical Simulation of Heat Transfer Flow Subject to MHD of Williamson Nanofluid with Thermal Radiation

by Muhammad Amer Qureshi

Symmetry 2021, 13(1), 10; https://doi.org/10.3390/sym13010010 - 23 Dec 2020

Cited by 57 | Viewed by 3566

Abstract

In this paper, heat transfer and entropy of steady Williamson nanofluid flow based on the fundamental symmetry is studied. The fluid is positioned over a stretched flat surface moving non-uniformly. Nanofluid is analyzed for its flow and thermal transport properties by consigning it [...] Read more.

In this paper, heat transfer and entropy of steady Williamson nanofluid flow based on the fundamental symmetry is studied. The fluid is positioned over a stretched flat surface moving non-uniformly. Nanofluid is analyzed for its flow and thermal transport properties by consigning it to a convectively heated slippery surface. Thermal conductivity is assumed to be varied with temperature impacted by thermal radiation along with axisymmetric magnetohydrodynamics (MHD). Boundary layer approximations lead to partial differential equations, which are transformed into ordinary differential equations in light of a single phase model accounting for

C u

-water and

T i O_{2}

-water nanofluids. The resulting ODEs are solved via a finite difference based Keller box scheme. Various formidable physical parameters affecting fluid movement, difference in temperature, system entropy, skin friction and Nusselt number around the boundary are presented graphically and numerically discussed. It has also been observed that the nanofluid based on

C u

-water is identified as a superior thermal conductor rather than

T i O_{2}

-water based nanofluid. Full article

(This article belongs to the Special Issue Plasma and Thermal Physics)

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Review

Jump to: Editorial, Research

27 pages, 2335 KiB

Open AccessReview

Particle-Laden and Droplet-Laden Two-Phase Flows Past Bodies (a Review)

by Aleksey Yu. Varaksin and Sergei V. Ryzhkov

Symmetry 2023, 15(2), 388; https://doi.org/10.3390/sym15020388 - 1 Feb 2023

Cited by 12 | Viewed by 2701

Abstract

A review of computational–theoretical and experimental works devoted to the study of the flow of bodies by two-phase (dispersed) flows is carried out. The features of particle motion in the vicinity of bodies of various shapes, as well as the effect of the [...] Read more.

A review of computational–theoretical and experimental works devoted to the study of the flow of bodies by two-phase (dispersed) flows is carried out. The features of particle motion in the vicinity of bodies of various shapes, as well as the effect of the dispersed phase on resistance and heat transfer, are considered. Some consequences of the interaction of particles and droplets with the surface of streamlined bodies (erosive destruction, gas-dynamic spraying, icing, glowing) are analyzed. Full article

(This article belongs to the Special Issue Plasma and Thermal Physics)

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25 pages, 391 KiB

Open AccessReview

Turbulence in Two-Phase Flows with Macro-, Micro- and Nanoparticles: A Review

by Aleksey Yu. Varaksin and Sergei V. Ryzhkov

Symmetry 2022, 14(11), 2433; https://doi.org/10.3390/sym14112433 - 16 Nov 2022

Cited by 18 | Viewed by 1662

Abstract

Turbulent flows are nonstationary in nature. Since the turbulent fluctuations of most flow parameters satisfy a symmetric Gaussian distribution, the turbulent characteristics have the property of symmetry in the statistical meaning. A widespread simplest model of turbulent flows is the model of “symmetric” [...] Read more.

Turbulent flows are nonstationary in nature. Since the turbulent fluctuations of most flow parameters satisfy a symmetric Gaussian distribution, the turbulent characteristics have the property of symmetry in the statistical meaning. A widespread simplest model of turbulent flows is the model of “symmetric” turbulence, namely, homogeneous isotropic turbulence (HIT). The presence of particles with non-uniform distribution of their concentration in the turbulent flow, even under HIT conditions, can lead to redistribution of different components of fluctuation velocities of the carrier gas, i.e., to the appearance of asymmetry. The subject of the review is turbulent flows of gas with solid particles. Particular attention is paid to the problem of the back influence of particles on carrier gas characteristics (first of all, on the turbulent kinetic energy). A review of the results of experimental and computational-theoretical studies of the effect of the presence of the dispersed phase in the form of particles on the parameters of the turbulent flow of the carrier gas phase has been carried out. The main physical mechanisms and dimensionless criteria determining the direction and magnitude of the impact of particles of different inertia on the carrier gas phase turbulence energy are described and analyzed. The peculiarities of the influence of particles on the turbulence energy of the gas for different classes of flows: homogeneous isotropic turbulence, homogeneous shear flow, and wall turbulence in a pipe (channel) have been considered. For the near-wall flow in the pipe, it is shown that the turbulizing effect of extremely low-inertia particles of sub-micrometer size (nanoparticles) is replaced by the laminarizing effect of low-inertia particles of micrometer size (microparticles), and then again it is replaced by turbulizing due to additional generation of turbulence in the wakes of large particles of millimeter size (macroparticles). The review is intended to some extent to fill in the currently existing gap associated with the absence of dimensionless criteria (or complexes of physical parameters) responsible for the direction (attenuation or enhancement) of turbulence modification, and the value of this change. Possible directions for further researches are given in the conclusion of the review. Full article

(This article belongs to the Special Issue Plasma and Thermal Physics)

21 pages, 16992 KiB

Open AccessReview

Heat Transfer on Micro and Nanostructured Rough Surfaces Synthesized by Plasma

by Alexey Victorovich Dedov and Viacheslav Petrovich Budaev

Symmetry 2022, 14(11), 2346; https://doi.org/10.3390/sym14112346 - 8 Nov 2022

Cited by 5 | Viewed by 2140

Abstract

The review summarizes recent experimental results of studying heat transfer on rough surfaces synthesized by plasma. The plasma-surface interaction leads to the stochastic clustering of the surface roughness with a high specific area breaking the symmetry of the virgin surface of the initial [...] Read more.

The review summarizes recent experimental results of studying heat transfer on rough surfaces synthesized by plasma. The plasma-surface interaction leads to the stochastic clustering of the surface roughness with a high specific area breaking the symmetry of the virgin surface of the initial crystalline materials. Such a surface is qualitatively different from the ordinary Brownian surface. The micro- and nanostructured surface consist of pores, craters, and nanofibers of size from tens of nanometers to tens of microns, which can provide new heat transfer properties related to a violation of the symmetry of the initial materials. In recent years, new results have been obtained in the study of heat transfer during phase change on plasma-modified surfaces in relation to energy, chemical, and cryogenic technologies. The objective of the review is to describe the specific structure of refractory metals after high-temperature plasma irradiation and the potential application of plasma processing of materials in order to create heat exchange surfaces that provide a significant intensification of two-phase heat transfer. Refractory metals with such a highly porous rough surface can be used as plasma-facing components for operation under extreme heat and plasma loads in thermonuclear and nuclear reactors, as catalysts for hydrogen production, as well as in biotechnology and biomedical applications. Full article

(This article belongs to the Special Issue Plasma and Thermal Physics)

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29 pages, 3560 KiB

Open AccessReview

Vortex Flows with Particles and Droplets (A Review)

by Aleksey Yu. Varaksin and Sergei V. Ryzhkov

Symmetry 2022, 14(10), 2016; https://doi.org/10.3390/sym14102016 - 26 Sep 2022

Cited by 25 | Viewed by 4676

Abstract

Single-phase vortices are a classic example of objects characterized by symmetry in the distribution of all main parameters. The presence of inertial particles (or droplets) in such objects, even with their initial uniform distribution in space, leads to symmetry breaking due to the [...] Read more.

Single-phase vortices are a classic example of objects characterized by symmetry in the distribution of all main parameters. The presence of inertial particles (or droplets) in such objects, even with their initial uniform distribution in space, leads to symmetry breaking due to the inverse effect of the dispersed phase on the characteristics of carrier vortices. A review of calculation-theoretical and experimental works devoted to the study of the motion of particles (or droplets) in various concentrated vortex structures, as well as their inverse effect on vortex characteristics, is conducted. The main characteristics (inertia, concentration) as well as dimensionless parameters (Reynolds, Stokes, Froude, Tachikawa numbers) determining the interaction between the dispersed phase and vortices are described. The results of available studies are analyzed in order to establish the peculiarities of particle (or droplet) behavior and stability of different vortex structures, including natural ones. The works analyzed in the review cover a wide range of inertia of the dispersed phase (Stk_f = 0.002 − 14.7) and vortex intensities (Re_Γ = 200 − 5000). Full article

(This article belongs to the Special Issue Plasma and Thermal Physics)

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