Generalized Poiseuille profiles in plasma flows in a stabilized region of a plasma generator

The equations of motion and energy balance in view of Joule heat release and temperature dependence of the coefficient of viscosity are used to generalize the Poiseuille solution to the case of stabilized laminar flow of low-temperature plasma in the channel of a plasma generator. Analytical relations are convenient for use in estimating various effects associated with a flow of plasma in channels and in processing the experimental results. The effect of the nonmonotonic temperature dependence of dynamic viscosity on the velocity profile is investigated. It is demonstrated that the nonmonotonic variation of viscosity over the channel cross section in the general case causes the emergence of two inflection points in the velocity profile; this, in turn, may cause the emergence of an instability due to the hydrodynamic mechanism of Kelvin-Helmholtz rather than to the mechanism of superheating. The numerical solutions of the Poiseuille and Elenbaas-Heller equations in a wide range of the working parameters of a plasma generator support the conclusions based on analytical solutions of these equations.__________Translated from Teplofizika Vysokikh Temperatur, Vol. 43, No. 2, 2005, pp. 165–174.Original Russian Text Copyright © 2005 by O. A. Sinkevich and S. E. Chikunov.     

Geometric approach to the degree of polarization for arbitrary fields

Abstract

The eigenvalue decomposition of the polarization matrix is employed to find out the geometric interpretation of the traditional degree of polarization and, in particular, of the degree of polarization for arbitrary electromagnetic fields put forward recently by Setälä et al. [2002, Phys. Rev. Lett., 88, 123902]. It is shown that both measures have similar geometric meaning as a measure for the purity of the polarization state. Possible extensions to the analysis are discussed.     

Effectiveness of mixing coaxial flows swirled in opposite directions

The mixing of coaxial turbulent flows swirled in opposite directions is experimentally studied. The effectiveness of this mixing is compared with mixing after an agitating grid.Notation z, r, cylindrical coordinate system - r₁, r₂ inside and outside radius of annular channel - H=r₂–r₁ radial gap in annular channel - y=(r–r₁)/H dimensionless radial coordinate - V(v_z, v_r, v) mean velocity vector - v, v_z pulsative components of velocity in the direction of the mean velocity vector and in the axial direction - P_*, P total and static pressure - , loss coefficients Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 41, No. 3, pp. 407–413, September, 1981.     

Excitation of the opposite acoustic flows in thermodynamically nonequilibrium gaseous media

It is shown that the acoustic wind direction may change in an acoustically active gaseous medium.     

Special features in the magnetization of polycrystals in alternating opposite magnetic fields

When a polycrystalline closed ferrimagnetic core is exposed to opposite ac magnetic fields with equal amplitudes, a nonzero ac magnetic field exists inside the core. As a result, an electric current is induced in a secondary coil wound over the primary one.     

Three-dimensional polarization states of monochromatic light fields

The 3×1 generalized Jones vectors (GJVs) [E(x) E(y) E(z)](t) (t indicates the transpose) that describe the linear, circular, and elliptical polarization states of an arbitrary three-dimensional (3-D) monochromatic light field are determined in terms of the geometrical parameters of the 3-D vibration of the time-harmonic electric field. In three dimensions, there are as many distinct linear polarization states as there are points on the surface of a hemisphere, and the number of distinct 3-D circular polarization states equals that of all two-dimensional (2-D) polarization states on the Poincaré sphere, of which only two are circular states. The subset of 3-D polarization states that results from the superposition of three mutually orthogonal x, y, and z field components of equal amplitude is considered as a function of their relative phases. Interesting contours of equal ellipticity and equal inclination of the normal to the polarization ellipse with respect to the x axis are obtained in 2-D phase space. Finally, the 3×3 generalized Jones calculus, in which elastic scattering (e.g., by a nano-object in the near field) is characterized by the 3-D linear transformation E(s)=T E(i), is briefly introduced. In such a matrix transformation, E(i) and E(s) are the 3×1 GJVs of the incident and scattered waves and T is the 3×3 generalized Jones matrix of the scatterer at a given frequency and for given directions of incidence and scattering.     

Degree of polarization in tightly focused optical fields

We analyze the degree of polarization of random, statistically stationary electromagnetic fields in the focal region of a high-numerical-aperture imaging system. The Richards-Wolf theory for focusing is employed to compute the full 3 x 3 electric coherence matrix, from which the degree of polarization is obtained by using a recent definition for general three-dimensional electromagnetic waves. Significant changes in the state of partial polarization, compared with that of the incident illumination, are observed. For example, a wave consisting of two orthogonal and uncorrelated incident-electric-field components produces rings of full polarization in the focal plane. These effects are explained by considering the distribution of the spectral densities of the three electric field components as well as the correlations between them.     

On steady plane magnetohydrodynamic flows with orthogonal magnetic and velocity fields

Hodograph transformation is employed to obtain a partial differential equation of second order, which is exploited to obtain solutions for plane viscous incompressible flows with orthogonal magnetic and velocity fields. This approach is illustrated through three examples.     

Energy transfer in a dielectric medium with allowance for the relaxation polarization

Energy relations of the macroscopic electrodynamics of a dielectric medium are considered with allowance for the relaxation polarization. An expression for the dielectric loss power flux density is obtained in the case of an arbitrary time-dependent electric field. An energy characteristic of the efficiency of insulators for capacitive energy storages is proposed.     

Energy modulations of a polarized proton beam associated with polarization reversal

The energy change associated with polarization reversal was studied for protons from an atomic beam polarized ion source after acceleration by a tandem accelerator. The modulation was found to be ≦0.5 eV.     

Phase-space representation and polarization domains of random electromagnetic fields

The phase-space representation of stationary random electromagnetic fields is developed by using electromagnetic spatial coherence wavelets. The propagation of the field's power and states of spatial coherence and polarization results from correlations between the components of the field vectors at pairs of points in space. Polarization domains are theoretically predicted as the structure of the field polarization at the observation plane. In addition, the phase-space representation provides a generalization of the Poynting theorem. Theoretical predictions are examined by numerically simulating the Young experiment with electromagnetic waves. The experimental implementation of these results is a current subject of research.     

Energy characteristics of simple shear granular flows

This work uses a 3-D discrete element simulation to calculate the elastic and kinetic energy for a nonuniform granular shear flow to determine whether the ratio of these energies is sufficient to identify specific flow regimes of granular materials in a fashion to other dimensionless parameters such as inertial number and dimensionless stiffness. We first obtain the critical packing fraction under isostatic compression, then analyze the mean and fluctuating parts of the elastic and kinetic energy as the granular flow reaches a steady state. External work performed on a system during granular flow partially dissipates into heat, while the remaining work is stored in particles as elastic and kinetic energy; thus processes occurring at a particle level not only control the energy transformation, but also affect the bulk behavior of a granular flow. The effective frictions are correlated with the mean elastic energy to mean kinetic energy ratio and it is interesting to find a power law function with an index of $-0.16$ for the systems used in this work. Analysis of this ratio’s ability to classify flow shows that its determination is quite sufficient to identify specific flow regimes of granular materials, even though energy has a scalar expression. Therefore, these energetics studies can provide a theoretical basis for unifying the mechanics of granular flows over the entire range of regimes.     

Multidirectional speckle photography of density fields in gasdynamic flows

Double-exposure speckle photography is employed experimentally to determine the fields of local density (temperature) values in a freely burning flame, as well as in the region of natural convection near a heated cylinder.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 56, No. 4, pp. 540–547, April, 1989.     

Characteristic features of low-temperature gas-discharge plasma flows

An investigation is made of the nature of gasdynamic anomalies accompanying the motion of shock waves and objects in a low-temperature nonequilibrium plasma. It is shown that these anomalies are caused by characteristic features of sound propagation in the plasma. Pis’ma Zh. Tekh. Fiz. 23, 88–93 (August 26, 1997)     

Method for study of particle concentration fields in dispersed flows

A technique for measuring local particle concentrations in dispersed flows is considered. Operation of the optoelectronic apparatus used is analyzed for single particle and multiparticle cases.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 41, No. 1, pp. 55–60, July, 1981.     

Characterization of neutron reference fields at US Department of Energy calibration fields

The Health Physics Measurements Group at the Los Alamos National Laboratory (LANL) has initiated a study of neutron reference fields at selected US Department of Energy (DOE) calibration facilities. To date, field characterisation has been completed at five facilities. These fields are traceable to the National Institute for Standards and Technology (NIST) through either a primary calibration of the source emission rate or through the use of a secondary standard. However, neutron spectral variation is caused by factors such as room return, scatter from positioning tables and fixtures, source anisotropy and spectral degradation due to source rabbits and guide tubes. Perturbations from the ideal isotropic point source field may impact the accuracy of instrument calibrations. In particular, the thermal neutron component of the spectrum, while contributing only a small fraction of the conventionally true dose, can contribute a significant fraction of a dosemeter's response with the result that the calibration becomes facility-specific. A protocol has been developed to characterise neutron fields that relies primarily on spectral measurements with the Bubble Technology Industries (BTI) rotating neutron spectrometer (ROSPEC) and the LANL Bonner sphere spectrometer. The ROSPEC measurements were supplemented at several sites by the BTI Simple Scintillation Spectrometer probe, which is designed to extend the ROSPEC upper energy range from 5 to 15 MeV. In addition, measurements were performed with several rem meters and neutron dosemeters. Detailed simulations were performed using the LANL MCNPX Monte Carlo code to calculate the magnitude of source anisotropy and scatter factors.