Numerical Simulation of Plasma Dynamics in a Nonuniform Magnetic Field

An efficient algorithm is proposed enabling numerical simulations of plasma dynamics in a nonuniform magnetic field. The present numerical data are in good agreement with experimental data obtained in a GOL-3 setup and with previous simulations. The experimentally observed effect of fast transfer of energy to ions is confirmed. __________ Translated from Prikladnaya Mekhanika i Tekhnicheskaya Fizika, Vol. 47, No. 1, pp. 35–45, January–February, 2006.     

Influence of a Longitudinal Magnetic Field on the Hall Effect in the Plasma Accelerator Channel

An analytic model of steady-state two-dimensional flows in coaxial plasma-accelerator channels in the presence of a longitudinal magnetic field is proposed. The solution of the problem is found in the smooth channel approximation for the MHD equations of an ideal two-component plasma. An example of the developing axisymmetric flows is given and the features of the plasma-dynamic processes are investigated. It is found that the Hall effect and the anode flow zone can be reduced using a longitudinal field and plasma rotation.     

Magnetic Field Effects on Axis-Switching and Instabilities in Rectangular Plasma Jets

The effect of an external magnetic field on the evolution of rectangular plasma jets is examined. Specifically investigated is the influence of a primarily axial magnetic field on the uniquely characteristic axis-switching phenomenon of rectangular jets and flow instabilities. The results indicate that the magnetic field decelerates the jet (more rapid spreading), prevents axis-switching and inhibits instabilities. The key physical mechanisms underlying the changes are (1) the ability of the magnetic field to reverse the direction of vorticity and (2) transfer of energy from kinetic to magnetic forms. This study has important implications for magneto-hydro-dynamic flow control and propulsion applications.     

Effect of Surface Conductivity on Magnetosphere Formation in Experiments with Laser Plasma flow over a Magnetic Dipole

This paper presents the results of laboratory experiments with laser plasma flow around a magnetic dipole which model the extreme compression of the Earthś magnetosphere by the plasma generated by high-power coronal mass ejections. Data on the formation of an artificial magnetosphere, the boundary-layer structure, and the size of the magnetosphere as a function of the magnetic moment are given. It is shown that in the presence of a conducting dipole shell modeling the ionosphere, conditions are created for the flow of intense longitudinal currents in the polar regions. It is established that the longitudinal currents have little effect on the position of the plasma stagnation point and the transition layer but make a significant contribution to the disturbance of the magnetic field in the magnetosphere.     

Convection in a Porous Medium with Variable Gravity Field and Magnetic Field Effects

The problem of convection in a variable gravity field with magnetic field effect is studied using methods of linear instability theory and non-linear energy theory. Then, the accuracies of both the linear instability and global non-linear energy stability thresholds are tested using a three-dimensional simulation. The strong stabilizing effect of gravity field and magnetic field is shown. Moreover, the results support the assertion that the linear theory is very accurate in predicting the onset of convective motion, and thus regions of stability.     

交变磁场对激光熔覆Fe基复合涂层组织结构及其耐磨性的影响

采用激光熔覆辅助电磁控制工艺在45钢表面合成了Fe-Cr-Si-B-C复合涂层.通过对熔覆层进行SEM、EDS和XRD表征,研究了外加交变磁场对涂层微观组织和物相结构的影响.结果表明:外加磁场可降低激光熔池固-液界面前沿液相的温度梯度和增加非均质形核率,促使粗大、方向性很强的柱状晶转变为均匀、细小的等轴晶,并能够消除熔覆层内的气孔和裂纹等缺陷,但其对熔覆层物相组成的影响不大.熔覆涂层由白色初生γ-(Fe,Cr)固溶体相和其间黑色的γ-(Fe,Cr)共晶相组成,同时含有少量Fe3(B,C)、Cr7(B,C)3、CrFeB等碳化物和硼化物.常温干摩擦磨损试验表明,外加磁场所制备的涂层耐磨性能得到明显提高,其磨损失重仅为未加磁场的43％,且摩擦系数波动较小.     

Permeability Changes During the Evolution of a Geothermal Field Due to the Dissolution and Precipitation of Quartz

The changes in permeability and porosity associated with quartz deposition in an evolving geothermal reservoir are investigated. We review the processes associated with permeability changes in a geothermal reservoir and also review recent work on quartz solubility and deposition rates. Porosity and permeability changes are calculated for two reservoir models. The first is a generic model of a Taupo Volcanic Zone geothermal reservoir and the second is based on the model of the deep circulation system at Kakkonda published by Hanano. We find that when a reservoir experiences BPD conditions during part of its lifetime the lower reservoir becomes impermeable and a hydrothermal circulation system is only present in the upper part of the reservoir.     

Nonlinear Responses of a Magnetoelastic Beam in a Step-Pulsed Magnetic Field

A theoretical study is carried out on the dynamics of a magnetoelastic beam being in a step-pulsed magnetic field. For this aim, the magnetic potential and elastic energies are determined for the beam and partial differential equations are established according to Hamilton's principle. It is proven that the magnetoelastic beam can give a variety of complex behavior in the case of step-pulsed field excitations. An intermediate regime of two-well chaos is observed. Theoretical findings were found to be in a good agreement with the experimental results for the specific system parameters. On leave from Institute of Physics, University of Bayreuth, 65440 Bayreuth, Germany An erratum to this article is available at .     

Deformation of a Superconducting Cylindrical Tube in a Perpendicular Magnetic Field

Stresses and displacements are obtained for an elastic superconductor in the form of an infinitely long, circular cylindrical tube subjected to an initially uniform magnetic field perpendicular to the tube's axis. The effect of the magnetic field penetration on the stressed state is assessed by solving the problem, firstly taking into account this penetration and, secondly, neglecting it. The problem involves the solution of a non-homogeneous biharmonic equation in two dimensions for the stress function. The special case of a circular cylinder is also given. Numerical calculations estimate the variation between the two cases for some quantities of practical interest. It is shown, in particular, that neglecting the penetration of the magnetic field in the elastic superconductor may induce a non negligible error in the appreciation of the stressed state.     

Hypersonic Flow Past the Spherical Nose of a Body in the Presence of a Magnetic Field

The hypersonic flow past the nose of a spherical body containing current sources generating a magnetic field is investigated theoretically and numerically. The magnetohydrodynamic (MHD) flow is analyzed on the basis of the complete system of Navier-Stokes equations containing the force and thermal MHD terms and the electrodynamic equations. Local and integral thermal and aerodynamic characteristics of the body are found. It is shown that the presence of a magnetic field makes it possible to reduce the heat flow to the body in the neighborhood of the stagnation point by several times. However, in this case the total body drag increases.     

旋转运动导电圆板的磁弹性参数振动分析

针对磁场中旋转运动圆板,在动能、应变能表达式基础上,根据哈密顿原理导出圆板的磁弹性振动方程．应用伽辽金积分法,得到横向磁场中旋转变速运动圆板的轴对称参数振动微分方程．通过坐标变换得到包含两个变系数项的马蒂厄振动方程．应用弗洛凯理论和平均法对系统的参数振动问题进行求解．通过数值计算得到周期稳定图、对应的振动响应特性图和相轨迹图．结果表明：在稳定区域内,系统的幅频曲线呈现为周期或概周期变化形式;在不稳定区内,系统的幅频响应曲线呈现为发散变化形式．     

直流稳恒磁场下高速钢/45~#钢环干滑动摩擦磨损特性研究

采用改进后的MPV-1500型摩擦磨损试验机,研究了常温下直流磁场对高速钢销/45#钢环摩擦副干滑动摩擦磨损特性的影响.结果表明:适当控制磁场强度可以降低磨损;磁场促进氧化,随着磁场强度增加,摩擦面生成的Fe2O3含量增加,磁场强度较大时,将有部分Fe3O4生成;载荷250 N,线滑动速度0.2 m/s下,随着磁场强度的增加,高速钢销试样的磨损量一直降低,45#钢环试样的磨损量、摩擦系数先降低后增加;磨损机制主要为氧化磨损和黏着磨损.     

Self-Localization of the Energy Supply During Pulse Ionization of a Supersonic Flow

The pulse ionization of the time-dependent quasi-two-dimensional flow developed during diffraction of a shock wave on a wedge is investigated experimentally. The redistribution of the pulse volume discharge plasma subjected to preionization by ultraviolet radiation from plasma sheets is investigated when the discharge is initiated in different stages of the time-dependent gas dynamic flow. Images of the plasma flow are compared with the corresponding fields of the gas dynamic flow parameters. It is shown that the pulse discharge plasma flows can be controlled due to the phenomenon of self-localization in a given flow zone of known shape. The local energy supply to the gasdynamic flow is simulated numerically using the experimental data.__________Translated from Izvestiya Rossiiskoi Academii Nauk, Mekhanika Zhidkosti i Gaza, No. 3, 2005, pp. 144–156.Original Russian Text Copyright © 2005 by Znamenskaya, Ivanov, Kryukov, and Kuli-Zade.     

载流圆板在磁场中的随机稳定性分析

本文根据大挠度板壳力学基础理论和电磁弹性力学理论,建立了载流圆板的非线性磁弹性随机振动力学模型,采用伽辽金变分法将其变换成非线性常微分动力学方程．通过拟不可积哈密顿系统的平均理论将该方程等价为一个一维伊藤随机微分方程．通过计算该方程的最大Lyapunov 指数判断该系统的局部随机稳定性,并进一步采用基于随机扩散过程的奇异边界理论判断该系统的全局稳定性．最后通过讨论该系统的稳态概率密度函数图的形状变化讨论了该动力系统的随机Hopf分岔的变化规律,并采用数值模拟对理论分析进行了验证．     

On the Electric Potential Induced by a Homogeneous Magnetic Field in a Turbulent Pipe Flow

In this paper we study a turbulent pipe flow of a weakly electrical conducting fluid subjected to a homogeneous magnetic field which is applied perpendicular to the flow. This configuration forms the basis of a so-called electromagnetic induction flow meter. When the Hartmann number is small so that modification of flow by the Lorenz force can be neglected, the influence of the magnetic field results only in a spatially and temporally varying electric potential. The magnitude of the potential difference across the pipe is then proportional to the flow rate and this constitutes the principle of the flow meter. In this study the flow and electric potential are computed with help of a numerical flow simulation called Large-Eddy Simulation (LES) to which we have added an equation for the electrical potential. The results of the LES have been compared with experiments in which the electric potential is measured as a function of time at several positions on the circumference of the pipe. Both the experimental and numerical results for the mean potential at the pipe wall agree very well with an exact solution that can be obtained in this particular case of a homogeneous magnetic field. Furthermore, it is found that fluctuations in the electric potential due to the turbulence, are small compared to the velocity fluctuations. Based on the results we conclude that electrical-magnetic effects in pipe flow can be accurately computed with LES.     

Plane Sources of Waves in the Presence of Magnetic Field

In this paper the generation of harmonic waves in an elastic magneticmaterial, which is a perfect conductor of electricity, isconsidered. It has been assumed that an infinite body is subjected tothe action of an initially constant magnetic fieldH = (H,0,0) and in the plane ax+by=0 acts a source ofdistortion. It has been shown that this source may produce bothtransverse and longitudinal waves and each of them consists of two parts,which propagate with different speeds. The amplitudes and speeds in dependence on theangle between the direction of wave propagation and the magnetic fieldintensity H have been discussed.     

MHD-Effects Due to the Hypersonic Motion of a Cylindrical Body in the Magnetosphere of a Planet for Mutually Perpendicular Orientations of the Generatrix and Magnetic Field

MHD-effects associated with the movement of a weakly conducting cylindrical body in a planetary atmosphere are analyzed numerically. The longitudinal axis of the body is perpendicular to the direction of motion and the field lines of the planetary magnetic field. In the calculations we used data similar to those for the collision of the Shoemaker-Levy 9 comet with Jupiter. The simulation is developed for two atmospheric levels: H100 km (magnetic pressure number R _H1) and H280 km (R _H1). It is shown that the maximum strength of the induced magnetic field is 2–3 orders of magnitude greater than the planetary magnetic field. For small R _H, analytical expressions giving a fairly reliable estimate for the field strength in the shock-compressed space ahead of the body are obtained.     

Solving the Equations of Motion of a Body in a Magnetic Field on the Basis of Polynomial Solutions

Polynomial solutions with a certain structure are obtained for the classical problem on the motion of a heavy solid with a fixed point. The conditions of existence of such solutions to the problem on the motion of a solid in a magnetic field are tested with regard for the Barnett–London effect. The condition of isoconicity of motion is removed. An estimate of the maximum degrees of the polynomials determining the solution is obtained for the general case