Influence of electron temperature on breaking of plasma oscillations

2019 ◽  
Vol 34 (2) ◽  
pp. 71-84 ◽  
Author(s):  
Eugene V. Chizhonkov ◽  
Alexander A. Frolov
Keyword(s):  
Numerical Experiments ◽  
Critical Level ◽  
Travelling Waves ◽  
Small Perturbations ◽  
Plasma Oscillations ◽  
Breaking Effect ◽  
Lagrangian Variables ◽  
Temperature Of Electrons ◽  
Good Agreement ◽  
Made In

Abstract The influence of thermal motion of electrons on the processes of relativistic plasma oscillations is studied analytically and numerically. It is shown that if the temperature of electrons grows and exceeds a certain critical level, then the breaking effect vanishes due to transformation of plasma oscillations into travelling waves. Analytical conclusions are made in the framework of the theory of small perturbations based on Lagrangian variables. Numerical simulation of the transformation is performed using three different algorithms constructed on the basis of the method of finite differences in Eulerian variables. The analytical results are in good agreement with numerical experiments.

scholarly journals Numerical modeling of plasma oscillations with consideration of electron thermal motion

2018 ◽  
pp. 194-206
Author(s):  
А.А. Фролов ◽  
Е.В. Чижонков
Keyword(s):  
Traveling Wave ◽  
Numerical Experiments ◽  
Plasma Temperature ◽  
Thermal Motion ◽  
Initial Region ◽  
Small Perturbations ◽  
Plasma Oscillations ◽  
Lagrangian Variables ◽  
Increasing Temperature ◽  
Good Agreement

Исследовано влияние теплового движения электронов на плоские нерелятивистские нелинейные плазменные колебания. Численно и аналитически показано, что при учете теплового движения колебания трансформируются в бегущую волну. При этом амплитуда волны растет с ростом температуры, что способствует выносу энергии из первоначальной области локализации колебаний. Для численного моделирования построена схема метода конечных разностей на основе эйлеровых переменных. При использовании лагранжевых переменных для приближения малых возмущений получены распределения максимумов электронной плотности в зависимости от температуры плазмы. Аналитические результаты находятся в хорошем соответствии с численными экспериментами. The effect of electron thermal motion on plane nonrelativistic nonlinear plasma oscillations is studied. It is shown numerically and analytically that when the thermal motion is taken into account, the oscillations are transformed to a traveling wave. At the same time, the wave amplitude grows with increasing temperature, which promotes the removal of energy from the initial region of oscillation localization. A finite-difference scheme is proposed for the numerical simulation on the basis of Eulerian variables. When using the Lagrangian variables to approximate small perturbations, the distributions of electron density maxima are obtained depending on the plasma temperature. The obtained analytical results are in good agreement with numerical experiments.

scholarly journals Artificial boundary conditions for numerical modeling of electron oscillations in plasma

2017 ◽  
pp. 65-79
Author(s):  
Е.В. Чижонков
Keyword(s):  
Boundary Conditions ◽  
Numerical Experiments ◽  
Asymptotic Methods ◽  
Electron Plasma ◽  
Dimensional Electron ◽  
Artificial Boundary ◽  
Plasma Oscillations ◽  
Breaking Effect ◽  
One Dimensional ◽  
Artificial Boundary Conditions

Асимптотическими методами изучается поведение функций, описывающих релятивистский эффект опрокидывания плоских одномерных электронных плазменных колебаний. Полученные формулы порождают различные виды искусственных граничных условий, которые анализируются с помощью численных экспериментов. Специально подобранная комбинация предложенных граничных условий используется для моделирования эффекта опрокидывания в пространственно двумерном случае. Часть расчетов была проведена на СКИФ МГУ "Чебышев" (МГУ им. М.В. Ломоносова). The behavior of the functions describing the relativistic breaking effect of plane one-dimensional electron plasma oscillations is studied by asymptotic methods. The obtained formulas generate various forms of artificial boundary conditions which analyzed by numerical experiments. A special combination of the proposed boundary conditions is used to simulate the breaking effect in the spatially two-dimensional case. A part of computation was performed on the "Chebyshev" Moscow University supercomputer system.

scholarly journals An approach to the modeling of a virtual thermal manikin

2014 ◽  
Vol 18 (4) ◽  
pp. 1413-1423 ◽  
Author(s):  
Dragan Ruzic ◽  
Sinisa Bikic
Keyword(s):  
Turbulence Models ◽  
Thermal Conditions ◽  
Heat Fluxes ◽  
Thermal Manikin ◽  
Flow Conditions ◽  
Body Segments ◽  
Nominal Size ◽  
Natural Flow ◽  
Good Agreement ◽  
Made In

The aim of the research described in this paper, is to make a virtual thermal manikin that would be simple, but also robust and reliable. The virtual thermal manikin was made in order to investigate thermal conditions inside vehicle cabins. The main parameters of the presented numerical model that were investigated in this paper are mesh characteristics and turbulence models. Heat fluxes on the manikin's body segments obtained from the simulations were compared with published results, from three different experiments done on physical thermal manikins. The presented virtual thermal manikin, meshed with surface elements of 0.035 m in nominal size (around 13,600 surface elements) and in conjunction with the two-layer RANS Realizable k-? turbulence model, had generally good agreement with experimental data in both forced and natural flow conditions.

scholarly journals Post-liquefaction reconsolidation of sand

2016 ◽  
Vol 472 (2186) ◽  
pp. 20150745 ◽  
Author(s):  
O. Adamidis ◽  
G. S. P. Madabhushi
Keyword(s):  
Void Ratio ◽  
One Dimensional ◽  
Geotechnical Centrifuge ◽  
Significant Damage ◽  
Pore Water Pressures ◽  
The One ◽  
Crucial Parameter ◽  
Excess Pore ◽  
Good Agreement ◽  
Made In

Loosely packed sand that is saturated with water can liquefy during an earthquake, potentially causing significant damage. Once the shaking is over, the excess pore water pressures that developed during the earthquake gradually dissipate, while the surface of the soil settles, in a process called post-liquefaction reconsolidation. When examining reconsolidation, the soil is typically divided in liquefied and solidified parts, which are modelled separately. The aim of this paper is to show that this fragmentation is not necessary. By assuming that the hydraulic conductivity and the one-dimensional stiffness of liquefied sand have real, positive values, the equation of consolidation can be numerically solved throughout a reconsolidating layer. Predictions made in this manner show good agreement with geotechnical centrifuge experiments. It is shown that the variation of one-dimensional stiffness with effective stress and void ratio is the most crucial parameter in accurately capturing reconsolidation.

The Productivity of Horizontal Wells in an In-Line Development System in Fields with Oil Rims

2021 ◽  
Author(s):  
Dmitriy Alekseevich Samolovov ◽  
Artem Igorevich Varavva ◽  
Vitalij Olegovich Polyakov ◽  
Ekaterina Evgenevna Sandalova
Keyword(s):  
Numerical Experiments ◽  
Single Phase ◽  
Analytical Formula ◽  
Horizontal Wells ◽  
Flow Equation ◽  
Development Pattern ◽  
Phase Flow ◽  
Single Phase Flow ◽  
Limited Applicability ◽  
Good Agreement

Abstract The study proposes an analytical method for calculating the productivity of horizontal wells in a line-drive development pattern in fields with oil rims. The paper presents an analysis of existing techniques and compares them with the results of detailed numerical experiments. It also shows the limited applicability of existing techniques. On the basis of the obtained solution of a single-phase flow equation for a line-drive pattern of horizontal wells, an analytical formula was obtained which more accurately describes the productivity of wells beyond the limits of applicability of existing methods. The resulting formula is in good agreement with the results of a detailed numerical experiment.

An analytical model of an I-cored coil located above a conductive material with a hole

2018 ◽  
Vol 82 (2) ◽  
pp. 21001
Author(s):  
Grzegorz Tytko ◽  
Leszek Dziczkowski
Keyword(s):  
Test Object ◽  
Middle Layer ◽  
Axially Symmetric ◽  
The Finite Element Method ◽  
Cylindrical Coordinate ◽  
Air Space ◽  
Through Hole ◽  
Tree Method ◽  
Good Agreement ◽  
Made In

The paper examines the problem of an axially symmetric I-cored coil located above a three-layered plate with a hole in the middle layer. A cylindrical coordinate system was applied, wherein the solution domain was truncated in the radial direction. The employment of the truncated region eigenfunction expansion (TREE) method resulted in deriving the final formulas for the change of the coil impedance with regard to the air space, and also pertaining to the test object without a flaw. Formulas for various configurations of the test object, among others for a surface hole, a subsurface hole and a through hole, have been presented. For the purpose of defectoscopy, the influence of the hole in the plate on the impedance components was investigated. The calculations were made in Matlab for frequencies from 100 Hz to 50 kHz. The obtained results were verified using the finite element method (FEM) in Comsol Multiphysics package. A very good agreement was observed in the case of both the resistance and reactance.

scholarly journals In-Depth Verification of a Numerical Model for an Axisymmetric RC Dome

Symmetry ◽  
2021 ◽  
Vol 13 (11) ◽  
pp. 2152
Author(s):  
Przemysław Czumaj ◽  
Sławomir Dudziak ◽  
Zbigniew Kacprzyk
Keyword(s):  
Three Dimensional ◽  
Spatial Models ◽  
Detailed Comparison ◽  
The Finite Element Method ◽  
Robot System ◽  
Engineering Structures ◽  
Computational Analyses ◽  
Computational Systems ◽  
Good Agreement ◽  
Made In

The designers of civil engineering structures often have to face the problem of the reliability of complex computational analyses performed most often with the Finite Element Method (FEM). Any assessment of reliability of such analyses is difficult and can only be approximate. The present paper puts forward a new method of verification and validation of the structural analyses upon an illustrative example of a dome strengthened by circumferential ribs along the upper and lower edges. Four computational systems were used, namely Abaqus, Autodesk Robot, Dlubal RFEM, and FEAS. Different models were also analyzed—two-dimensional (2D) and three-dimensional (3D) ones using continuum, bar, and shell finite elements. The results of the static (with two kinds of load—self-weight and load distributed along the upper ring) and modal analyses are presented. A detailed comparison between the systems’ and models’ predictions was made. In general, the spatial models predicted a less stiff behavior of the analyzed dome than the planar models. The good agreement between different models and systems was obtained for the first natural frequency with axisymmetric eigenmodes (except from the Autodesk Robot system). The presented approach to the verification of complex shell–bar models can be effectively applied by structural designers.

scholarly journals A numerical study of cell merger over Cuba – Part I: implementation of the ARPS/MM5 models

2006 ◽  
Vol 24 (11) ◽  
pp. 2781-2792 ◽  
Author(s):  
D. Pozo ◽  
I. Borrajero ◽  
J. C. Marín ◽  
G. B. Raga
Keyword(s):  
Mesoscale Model ◽  
Numerical Study ◽  
Initial Boundary ◽  
Radar Data ◽  
Horizontal Resolution ◽  
Convective Systems ◽  
Maximum Reflectivity ◽  
Radar Echoes ◽  
Good Agreement ◽  
Made In

Abstract. On 21 July 2001 a number of severe storms developed over the region of Camaguey, Cuba, which were observed by radar. A numerical simulation was performed in order to realistically reproduce the development of the storms observed that day. The mesoscale model MM5 was used to determine the initial, boundary and update conditions for the storm-scale simulation with the model ARPS. Changes to the source code of ARPS were made in order to assimilate the output from the MM5 as input data and a new land-use file with a 1-km horizontal resolution for the Cuban territory was created. A case representing the merger between cells at different stages of development was correctly reproduced by the simulation and is in good agreement with radar observations. The state of development of each cell, the time when the merger occurred, starting from the formation of clouds, the propagation motion of the cells and the increase in precipitation, due to the growth of the area after the merger, were correctly reproduced. Simulated clouds matched the main characteristics of the observed radar echoes, though in some cases, reflectivity tops and horizontal areas were overestimated. Maximum reflectivity values and the heights where these maximum values were located were in good agreement with radar data, particularly when the model reflectivity was calculated without including the snow. The MM5/ARPS configuration introduced in this study, improved sensibly the ability to simulate convective systems, thereby enhancing the local forecasting of convection in the region.

Observations on the Performance of Vibration-Isolated Railway Track

1997 ◽  
Author(s):  
Hugh E. M. Hunt
Keyword(s):  
Travelling Waves ◽  
Surrounding Medium ◽  
Railway Track ◽  
Relative Speed ◽  
Tunnel Wall ◽  
Infinite Beam ◽  
Slab Track ◽  
Torsional Response ◽  
Made In

Abstract Vibration generated by underground railways is difficult to control because of the very limited space available in a tunnel. A popular approach is to use ‘floating slab track’ whereby the rails are fixed to a large concrete foundation separated from the tunnel wall by a resilient material. This paper investigates some of the vibration characteristics of floating slab track from measurements made in situ. These measurements are compared with the theoretical response of an infinite beam on an elastic foundation taking into account the torsional response of the beam. The transmission of vibration through the tunnel wall and into the surrounding medium is discussed with reference to the relative speed of travelling waves and the coincidence frequencies.

Effect of Shallow Water on a Mathematical Hull at High Subcritical and Supercritical Speeds

1986 ◽  
Vol 30 (02) ◽  
pp. 85-93
Author(s):  
A. Millward ◽  
M. G. Bevan
Keyword(s):  
Shallow Water ◽  
Wave Theory ◽  
Hull Form ◽  
Towing Tank ◽  
Resistance Peak ◽  
Good Agreement ◽  
Made In

Experiments have been made in a towing tank to measure the resistance of a mathematical hull form in deepwater and in shallow water at high subcritical and supercritical speeds. The data have been compared with calculations using linearized wave theory for the same hull shape. The results have shown fairly good agreement, with the greatest differences occurring near the subcritical resistance peak.

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