Diffusion of superintense pulsed magnetic fields

The phenomena accompanying the diffusion of superintense pulsed magnetic fields in metals are studied. Solutions are obtained for the diffusion of a constant superintense magnetic field into a half-space with a plane boundary and for the diffusion of an axial concentrated magnetic field. The limiting magnetic fields which can be obtained in various experimental devices are found. The results are compared with experiment.     

Penetration of intense pulsed magnetic fields into a conductor

Translated from Zhurnal Prikladnoi Mekhaniki i Tekhnicheskoi Fiziki, No. 5, pp. 7–12, September–October, 1989.     

Measurements of the intensity of high pulsed magnetic fields by the faradayeffect in flintglass

Summary In this paper we discuss a method of measuring high pulsed magnetic fields by means of the Faraday method i.e. we measure the rotation of the plane of polarization caused by a magnetic field in an optical medium, in our experiment flintglass F.D. For the production of the intense transient magnetic fields (450,000 Oersted) we use energy obtained from a bank of charged condensors (1000 F).The value of the Verdet constant is determined by comparing the results of the induction method with those of magneto-optical Faraday method. A new design for the construction of coils of rectangular cross-section is also given.Stagair research fellow of the Belgisch Nationaal fonds voor Wetenschappelijk onderzoek.     

Acceleration of conductors to supersonic speeds in a pulsed magnetic field

The effect of the shape of the current-density curve and the initial angle of acceleration on the velocity of projection of current-carrying conductors in a pulsed magnetic field produced in the discharge of a capacitive energy accumulator is investigated. A variational problem is solved to determine the optimum current-density function in the projected body for a given magnetic-induction function. It is shown that the relation j =KB, where K is a constant, gives the maximum velocity. For a uniform magnetic field varying as a damped sinusoid, expressions are obtained for the current density in the accelerated body, the velocity of projection, and the acceleration path. It is shown that there is an optimum initial angle of acceleration depending on the amplitude and frequency of the accelerating force and the acceleration path. A procedure is presented for the approximate design of a hypersonic electromagnetic accelerator. In accord with the conclusions of the theory an experimental arrangement is set up and a study is made of the projection of conductors in a pulsed magnetic field. A maximum velocity of 10.5 km/sec is obtained for 0.16-mm diameter aluminum wires.Translated from Zhurnal Prikladnoi Mekhanika i Tekhnicheskoi Fiziki, No. 3, pp. 44–53, May–June, 1974.     

KINEMATICAL FORCE-FREE FIELDS OF A MAGNETIC ARCH

I.Introducti0nCosmicmagneticfieldswhichoccurinregionsofhighelectricalconductivityandlowdensitymightoftensatisfytheforce-freeconditioncurlH=a(r,t)H(l.l)whereHdenotesthedensityofthemagneticfleld,and2issomescalarfunctionofpositionandtime,sincethepressuregrad…     

Kinematic characteristics of magnetic fluid sloshing in a rectangular container subject to non-uniform magnetic fields

 The dynamic behavior of a magnetic fluid in a laterally vibrated rectangular container subject to a non-uniform vertical magnetic field has been investigated. Flow behavior was observed using the ultrasound velocity profile measuring technique. The effect of the magnetic field on the resonant frequency of the fluid-container system is discussed. Experimental results are compared with the results obtained from nonlinear theory using the perturbation method. Received: 27 May 1997/Accepted: 26 March 1998     

The measurement of small forces by means of a moving coil meter with an application to magnetic susceptibility measurements

Summary A method is described for the measurements of small forces (10⁻⁵ – 10⁻³ newton) on a sample weighing a few grams. This sample is placed on a bar which is fixed on the turning coil of an ordinary switchboard current meter. The force on the sample can be compensated by the Lorentz force on the current through the coil. This method avoids a great many of the usual constructional difficulties of such apparatus and leads to a robust instrument which is easy to handle and to. automatize, thus being of interest for use outside the laboratory. Especially this possibility has induced us to choose as an example a magnetic susceptibility balance. For magnets of field strength up to 20 000 oerstedt the precision obtained for the measured susceptibility amounts to one tenth of a percent.     

Cyclic variability of pulsed spray vapor fields

 A two wavelength extinction technique is used to quantitatively measure the temporal fuel vapor field produced by pulsed automotive fuel injectors. Line-of-sight measurements are spatially deconvoluted to yield a picture of the overall, cycle-averaged, radial vapor concentration profiles. Vapor measurements are also given for single, consecutive, injection pulses, showing cycle-to-cycle variations in the vapor field. Methods to characterize the cyclic variability in the vapor field of a pulsed spray are discussed. As an illustrative example, the differences between an air assist and a non-air assist injector are shown as a function of duty cycle and axial location. Received: 11 August 1997/Accepted: 10 February 1998     

The application of coherent anti-Stokes Raman scattering to temperature measurements in a pulsed high enthalpy supersonic flow

Broadband single pulse coherent anti-Stokes Raman scattering (CARS) experiments employing a folded box phase matching geometry in a shock tunnel flow are presented. Rovibrational spectra of molecular nitrogen, produced at the exit of a pulsed supersonic nozzle for a range of flow enthalpies, are examined. Difficulties peculiar to the application of the optical technique to a high enthalpy pulsed flow facility are discussed and measurements of flow temperatures are presented. Theoretically calculated values for temperatures based upon algorithms used to determine shock tunnel flow conditions agree well with experimental measurements using the CARS technique.     

Thermal instability of a boundary layer subjected to external electric and magnetic fields

This paper presents a numerical study of the electrical and magnetic fields on thermal instability in a boundary layer. The criterion on the position marking on the onset of longitudinal vortices is defined in the present paper. The results show that the onset position characterized by the Grashof number depends on the Prandtl number, the Reynolds number, the wave number, the electric field parameter, and the Hartmann number. The flow becomes more stable as the magnetic field increases. However, the destabilizing effect is found on the flow when the negative electric field parameter is applied. The results of the present numerical prediction show reasonable agreement with the experimental data in the case of zero Hartmann number and zero electric field parameter in the literature. Copyright © 2010 John Wiley & Sons, Ltd.     

The effect of induced magnetic fields on convective stability of a conductive liquid carrying a current

The stability of equilibrium in a plane layer of an electrically conductive liquid located in electric and magnetic fields is considered. The effect of an unperturbed induced magnetic field and its perturbations on stability of this type is considered. The stability is analyzed nonlinearly.Translated from Izvestiya Akademii Nauk SSSR, Mekhanika Zhidkosti i Gaza, No. 1, pp. 102–110, January–February, 1974.     

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论证了作图法的几何原理------四点共圆. 介绍了四点共圆作图法在计算机辅助下的求解 和构建复杂滑移线场的过程. 并以有心扇形场为例,演示了该方法的解题步骤. 通过实例计 算,将该方法的求解结果与作者用数值积分法和矩阵算子法的求解结果作了比较,证明该方 法计算精度高、绘图质量好.     

线圈脉冲电流对破甲弹金属射流箍缩特性的影响

为了研究线圈脉冲电流参数对破甲弹金属射流箍缩特性的影响, 提出了均匀线圈中脉冲电流作用下不均匀粗细金属射流磁感应强度、感应电流密度及箍缩电磁力分布的理论模型, 建立了线圈与金属射流作用的有限元模型, 分析了励磁线圈中所施加脉冲电流参数对金属射流的影响规律。结果表明, 随着励磁线圈中所施加脉冲电流幅值的增大, 金属射流中的感应电流密度、磁感应强度及电磁力也随之增大, 励磁线圈中所施加的脉冲电流幅值J_max≥1×1010 A/m2, 才能保证金属射流可靠变形;随着励磁线圈中所施加脉冲电流频率的增加, 金属射流中的感应电流密度、磁感应强度及电磁力整体均呈现一定程度的趋肤效应, 且在一定的频率范围内, 趋肤层逐渐变薄, 分析得知, 当励磁线圈中脉冲电流的频率满足50 kHz≤f≤100 kHz时, 就能够保证金属射流发生有效变形, 进而延缓金属射流箍缩直至断裂的过程。     

Interaction of a jet of plasma with electric and magnetic fields

Summary A generalized ohm's law is used to predict changes in the direction and magnitude of the momentum of a stream of plasma in a crossed field accelerator in terms of plasma properties and species temperatures and concentrations. Measurements are reported of accelerator thrust, plasma jet deflection angle, current-voltage characteristics, accelerator inlet momentum, cooling rates and cross-arc power input for argon and helium plasmas. Estimates are given of the mean values of some of the parameters of argon and helium plasma obtained under nonequilibrium conditions. These results are compared with other methods requiring the assumption of LTE.This work was supported in part by the U.S. Air Force through the Propulsion Division, Directorate of Engineering Sciences, Office of Aerospace Research, AFOSR, under contract AF 49(638)-1445.     

Nonlinear dynamics of a sinusoidally driven lever in repulsive magnetic fields

We study bifurcations and chaotic behavior of a periodically forced lever that is magnetically controlled. The system is extremely simple and low cost and can be assembled in a very short time. Both the theoretical simulations and the experimental measurements exhibit regions of periodic and chaotic behaviors, depending on the system parameters. Amplitude jumps, hysteresis and bistable states are also observed. The wide possibilities of varying the system parameters make the experiments suitable for demonstrations. Good agreements are found between our theoretical results and experimental ones.     

Magnetothermoelastic transient response of a functionally graded thick hollow sphere subjected to magnetic and thermoelastic fields

In this article, an analytical method is developed to obtain the response of magnetothermoelastic stress and perturbation of the magnetic field vector for a thick-walled spherical functionally graded materials (FGM) vessel. The vessel, which is placed in a uniform magnetic field, is subjected to an internal pressure and transient temperature gradient. Using the Hankel and Laplace transform techniques, the dynamic equation of magnetothermoelastic is solved and the radial and circumferential stresses as well as the perturbation of the magnetic field vector for a typical material are obtained. Moreover, the effect of magnetic field vector and material inhomogeneity on the stresses is investigated.