Mass transfer effects on the generalised vortex flow over a stationary surface with or without magnetic field

The effect of injection and suction on the generalised vortex flow of a steady laminar incompressible fluid over a stationary infinite disc with or without magnetic field under boundary-layer approximations has been studied. The coupled nonlinear ordinary differential equations governing the self-similar flow have been numerically solved using the finite-difference scheme. The results indicate that the injection produces a deeper inflow layer and de-stabilises the motion while suction or magnetic field suppresses the inflow layer and produces stability. The effect of decreasingn, the parameter characterising the nature of vortex flow, is similar to that of increasing the injection rate.     

Unsteady motion of a fluid near a disk rotating in a magnetic field

The effect of a magnetic field on the velocity distribution in a fluid close to an unsteadily rotating disk is investigated.Notation r, , and z coordinates in the radial, circular, and axial directions - t time - u, v, and w radial, circular, and axial velocity components - u₀ radial velocity of external potential flux - v₀ circular velocity of the disk - (t) angular velocity of the disk - p pressure - density - v kinematic viscosity - B₀ characteristic of the applied magnetic field - electrical conductivity of fluid - R and Z dimensionless coordinates in the radial and axial directions - =Z/2 dimensionless coordinate - T dimensionless time - U, V, and W radial, circular, and axial components of dimensionless velocity - P dimensionless pressure - a, , and ₀ constants with dimensionality t^–1 - m, n, and positive numbers - k =a constant - = = B ₀ ² / parameter characterizing the magnetic field     

Transverse motion of charged particle with oscillating charge in magnetic field

It is established that a particle bearing an oscillating electric charge can exhibit transverse drift in a homogeneous magnetic field. This drift has a resonance character and cannot be eliminated even at small amplitudes of charge oscillations.     

低温涡街流场特性数值仿真研究

通过FLUENT对典型的涡街流量计在低温流体中的卡门涡街流场特性进行理论分析和数值仿真,并与常温工况下的涡街流场进行比较,分析低温流体的旋涡分离过程,得出流量与涡街分离频率的对应关系.研究表明,数值仿真方法成本低,适于模拟复杂流场,为低温涡街流量计在涡街发生体形状和压电振动传感器采样位置的设计与优化提供理论依据.     

Directional solidification of eutectic and off-eutectic Au-Co composites with and without magnetic field

A fibrous eutectic with Co fibres embedded in a Au-matrix can be obtained at G/v ≥ 2×10⁵ deg/cm² whereG = temperature gradient andv = growth velocity. Interfibre spacing 2R can be described byR ² v=1.2×10⁻¹¹ cm³/sec. Below G/v=2×10⁵ deg/cm² cellular growth is observed. Fibre to blade transitions have been found over the entire range of growth velocities employed, i.e. between 10⁻⁵ and 10⁻²cm/sec and are thought to be due to local growth perturbations. Composite growth under the influence of a magnetic field produces two effects: an orienting effect and a shape and size modification. Orienting occurs at slow growth rates, preferably, in hypereutectic alloys and is explained as a magnetic aligning of the ferromagnetic primary Co-precipitates. The shape and size modification which results in thick and segmented, caterpillar-like Co fibres, appears to be independent of growth rate (within the limits indicated above), occurs mainly in cell boundaries at all compositions, including hypoeutectic ones, and is thought to be due to a field induced enhancement of local temperature gradients.     

On the motion of macroparticles in inhomogeneous magnetic field

The behavior of macroparticles that form a near-wall dust in tokamaks is described with allowance for the force of gravity, force of entrainment by plasma ion flux, and Lorentz force acting on the motion of charged macroparticles in an inhomogeneous magnetic field. It is shown that, in some cases, the effect of induced currents that arise in the particles during this motion must in some cases be taken into account.     

Cooling curves analysis of aluminium solidified without and with magnetic or electric field

Abstracts are not published in this journal This revised version was published online in November 2006 with corrections to the Cover Date.     

Calculation of compressible flow in a short vortex chamber

A method for calculating a compressible turbulent flow in a short vortex chamber that incorporates calculations of the boundary layer at the end walls by the integral method and of the discharge by the theory of an ideal atomizer has been proposed. The magnitudes of pressure and circulation on the radius of the outlet orifice of the chamber, obtained in determining the boundary layer, have been used as input parameters in calculating the discharge, and the gas process has been regarded as isothermal. Favorable agreement between the calculated results and the experimental data has been found. __________ Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 79, No. 5, pp. 152–158, September–October, 2006.     

Cooling curves analysis of aluminium solidified without and with magnetic or electric field

Abstracts are not published in this journal     

尖劈状磁场中磁流体磁性微粒的受力分析

通过有限元方法对尖劈形磁场中磁流体磁性微粒所受的磁场力进行了数值分析,分别给出了磁场气隙处磁通量和磁场强度随不同气隙宽度和夹角的变化规律.在此基础上,利用虚位移法和麦克斯韦应力张量法计算磁流体磁性微粒在气隙上方所受的磁场力.结果表明,随着气隙宽度的减小,磁通量、磁场强度和磁场力明显增加;随着气隙夹角的增加,磁通量、磁场...     

Control of cathodic arc spot motion under external magnetic field

A closed circular transverse magnetic field is designed to control the spot motion of a cathodic arc on a large rectangular target. Stable and controllable spot motion is observed from both graphite and copper. The arc stability, spot velocity, and etched pattern on the cathode surface are studied systematically. Circular tracks are etched on the target surface by the repetitive spot movement and the surface morphology and resistivity of the cathode materials influence the spot velocity.     

Uniqueness of compressible micropolar fluid flows

The paper examines the uniqueness of compressible micropolar fluid flows over an arbitrary region $\text{R(t)}$ with a smooth boundary $\text{?R(t)}$. It is shown that there is at most one solution of the flow equations and boundary conditions which corresponds to suitably assigned initial values of the density, velocity, microrotation and temperature fields. The analysis rests on the use of differential inequalities involving the time derivatives of certain energy integrals.     

Question of the motion of a system of sequential coaxial vortex rings in a homogeneous fluid

Results are presented of an experimental investigation of the singularities of the motion of a system of interacting toroidal vortices in a homogeneous fluid.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 56, No. 1, pp. 26–28, January, 1989.     

Decimeter-wave impedance measurement of Y- and Tl-based superconductors with and without an external magnetic field

The real part of low-temperature surface impedance of samples of high-T _c superconductors in the YBa₂ Cu₃O_6+x ceramic system was studied by the method of registration of the ownQ-factor of coaxial shortringed cylindrical resonator constructed entirely from examined material. For ceramic samples of high-T _c superconductors in the Tl₂Ba₂Ca₂Cu₃O system the same measurements were made with the help of coaxial Al resonator. The wavelength of radio frequency field equals 70cm. The dependence of the impedance of Y-based superconductors on weak magnetic field at helium temperature is close to the square law. The magnitude of impedance at temperature of liquid helium for Y-based superconductors composes 0,04 ohm, for Tl-based superconductors −0,01 ohm respectively which correlates with the statement of the presence of giant resonant absorption of radio frequency field power.     

Stability of magnetic fluid penetration through a porous medium with uniform magnetic field oblique to the interface

Recent work has shown that the fingering instability, which develops when a more viscous fluid is pushed through the voids of a porous medium or through a Hele-Shaw cell by a less viscous fluid, can be prevented if a magnetic field is applied tangential to a flat fluid interface separating magnetizable and non-magnetizable fluids. This earlier work is extended here by considering equilibrium magnetic field components both perpendicular and parallel to the flat interface. The tangential field component stabilizes those waves traveling along the field lines while the normal field is destabilizing. The analysis is developed through a general set of relations for perturbation field and flow interfacial variables defined for a "prototype" magnetizable fluid layer which can be used to describe the small signal stability characteristics of layered fluid systems. In a uniform tangential magnetic field geometry, experimental results of the most unstable wavelength in a Hele-Shaw cell are shown to agree well with theory.     

Relativistic Cherenkov microwave oscillator without a guiding magnetic field

A relativistic Cherenkov microwave oscillator without a guiding magnetic field has been designed, constructed, and tested in which a continuous cylindrical electron beam propagates in a short (L ≈ 3λ, λ being the radiation wavelength) resonant slow-wave structure. The electron beam is energy-modulated at the input of the interaction space, which provides conditions for the energy exchange at a wave phase velocity exceeding the particle velocity. The effective beam-wave coupling is provided by a nearly homogeneous profile of the longitudinal electric field component of the synchronous wave in the interaction space cross section. The efficiency of power conversion from high-current electron beam to electromagnetic radiation at E₀₁ mode is about 8% at a maximum output pulse radiation power of 1.2 ± 0.3 GW and a working frequency of 4.05 GHz.     

Eigenvalue solutions for free motion of electroconductive plate in magnetic field

Free flexural motion of a homogeneous plate in a large magnetostatic uniform field is re-examined. Linearized theory of thin plates made of an elastic electroconductive non-magnetizable isotropic material is applied. The intermediate approach (three-dimensional in the electromagnetic part and two-dimensional in the mechanical part), four two-dimensional models using various electromagnetic thickness assumptions as well as the perfect conduction case are reviewed. The resulting eigenvalue solutions of first-order approximation with respect to the bias magnetic field are compared analytically and numerically for both the in-plane and transverse bias magnetic field. Some estimations and improvements are included.     

On an asymptotic case of plane turbulent motion of a weakly conducting rotating fluid in the presence of a magnetic field

Summary The final period of decay of homogeneous turbulence in a weakly conducting rotating fluid in the presence of a magnetic field is investigated. By asymptotic expansion techniques, the expressions of the kinetic and magnetic energy tensors are established. After a first stage similar to the non-rotating case, it is shown that modulated plane turbulence occurs when both the applied magnetic field and the axis of rotation are parallel.Aspirant au Fonds National Belge de la Recherche Scientifique.     

Prediction of leading-edge vortex behaviour to supplement the suction analogy

Summary An analytical treatment is presented which permits the prediction of the strength and path of leading-edge vortices on thin wings of delta-like planform from a knowledge of the behaviour of the linearized approximation to the attached flow past the wing. This supplements the leading-edge suction analogy, which predicts the forces and moments acting on the wing from the same input. The fundamental assumption is that the vortex lies close to the leading edge. It is represented by a single line-vortex and the presentation is confined to low-speed flow and plane wings. The treatment is independent of the way the basic attached flow is calculated. Results are shown for two simple planforms, using inputs from three-dimensional lifting-surface theory and from slender-body theory.     

Influence of temperature field on stability of fluid motion between rotating cylinders

The Rayleigh method is used to obtain relations giving the influence of the amount and direction of heat flow on the stability of a fluid between rotating cylinders.