Numerical Analysis of the Characteristics of an Arc in Laminar and Turbulent Gas Flows

The equations of magnetic gas dynamics are used to calculate the characteristics of an electric arc in a plasmotron channel versus the gas flow rate. The results obtained with the aid of the laminar and the two-parameter k– model of turbulence with allowance for deviations from equilibrium in the plasma and for the swirling of the gas are compared with experimental data. The stability of a laminar flow to the effect of weak hydrodynamic perturbations is investigated.     

Heat Exchange with Horizontal Cylinders in a Centrifugal‐Bubbling Bed

The authors present results of an analysis of experimental data on heat exchange on horizontal cylinders in rotating gasliquid flow. The hydrodynamic parameters of a thin film in a centrifugalbubbling bed have been determined based on the mathematical modeling of a film flow in the case of a highvelocity gasliquid flow about it. Results of a generalization of the data on heat exchange are given, and the hydrodynamic stability criteria for the film flow on the cylinder surface are evaluated.     

Wave Motion of Solid Particles in a Pulsed Gas Flow

The effect of lowfrequency pulsations of gas on the motion of solid particles has been studied on the basis of numerical solution of equations of the dynamics of a monodisperse gas suspension with account for interphase forces of hydrodynamic drag, virtual masses, and forces due to nonstationary effects around particles. It is found that at certain parameters gas pulsations lead to enhancement of interphase heat transfer. The dependences of the time of particle residence in a pneumochannel on the frequency of gas pulsations have been obtained.     

Adsorption Systems of Natural Gas Storage and Transportation at Low Pressures and Temperatures

Questions of the development and investigation of thermally regulated natural gas storage and transportation systems of a new type using sorbents are considered. The results of fullscale tests of the adsorption compressed gas cylinder system for the GAZ53 truck are described.     

Hydrodynamic reaction to accelerated onedimensional motion of gas bubbles of variable volume in an unbounded liquid

A solution is given for the problem of the hydrodynamic reaction of an ellipsoidal gas bubble of variable volume to accelerated motion and the relation between the value of the apparent mass and the eccentricity of the bubble.Notation (,) velocity potential - V velocity of motion of the bubble with respect to the liquid - (, ) velocity potential of the near field - T₂ kinetic energy of the liquid due to the variation in bubble volume - F_r reaction force of the liquid - B₁ momentum of the liquid - _e apparent mass of the ellipsoid - density of the liquid - V_e volume of the ellipsoidal bubble Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 39, No. 1, pp. 47–50, July, 1980.     

Application of the Electrochemical Method for Measuring the Fluid Velocity in a Two‐Phase Bubble Flow

A technique for measuring the fluid velocity in a twophase flow using a combination of the electrochemical method and the conduction method is described. The point of this technique is numerical analysis of complete realizations of signals from the electrodiffusion velocity transducer. The dependence of the results of measurements of local hydrodynamic characteristics of the bubble flow on the level of gasphase cutting out has been investigated. The measurement data for the local gas content, the fluid velocity, and the velocity pulsations during bubble mixture motion in a tilted channel are presented.     

Hydrodynamics of a granular medium

The hydrodynamic characteristics of loose granular media are studied experimentally, with due allowance for particular aspects of the pore space structure (the sinuous nature of the paths of penetration and the efficiency with which the intergranular spaces take part in filtration); the results show that Re 80, up to Reynolds numbers of Re_cr 5.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 21, No. 3, pp. 452–459, September, 1971.     

Collisional Damping of the Collective Oscillations of a Trapped Fermi Gas

We consider a Fermi gas confined by a harmonic trapping potential and we highlight the role of the Fermi–Dirac statistics by studying frequency and damping of collective oscillations of quadrupole type in the framework of the quantum Boltzmann equation, in which statistical corrections are taken into account in the collisional integral. We are able to describe the crossover from the collisionless regime to the hydrodynamic one by introducing a temperature-dependent relaxation time _Q . We show that, in the degenerate regime, the relaxation rate ^–1 _Q exhibits a temperature dependence different from the collision rate . We finally compare the collisional properties of the Fermi gas with the ones of the Bose gas for temperatures above the Bose–Einstein condensation.     

Plasticity of perfect crystals

A specific type of plasticity induced by complicated pointlike thermally-induced defects is proposed. In this case it is possible to derive a system of hydrodynamic equations describing bulk crystal dynamics and a set of boundary conditions for them for both crystal-crystal and crystal-liquid interfaces. A certain limit of those gives the boundary condition introduced by Herring.² The obtained system describes a phenomenon of equilibrium plasticity. The defect-induced motion of rigid bodies through the crystal is investigated on the basis of presented equations.     

The scattering of water waves by an array of circular cylinders in a channel

The full linear problem of the scattering of water waves by an array of N bottom-mounted vertical circular cylinders situated in a channel of constant depth and width is solved using the method of multipoles. A simple formula is derived for the velocity potential in the vicinity of a cylinder, and in particular on the cylinder surfaces, which allows hydrodynamic quantities such as forces to be easily evaluated. The simplicity of the solution makes the evaluation of quantities of interest straightforward and extensive results are given. An approximate solution for the forces on the cylinders, based on the assumption that the wavelength of the incident wave is long compared with the cylinder radii, is also given, and this is compared with results from the exact linear solution.     

Parameters of plane separated flow

Data of computer calculations are presented for the parameters of motion of a compressible gas in the self-similar turbulent mixing zone following separation from a solid surface. Two kinds of boundary condition are examined. On the basis of the integral relations, a calculation is made of the influence of the momentum thickness of the initial boundary layer. The results obtained may be used for calculating closed and open stagnant zones in various problems.     

A possible mechanism of vibroseismic action on an oil-bearing bed

A possible mechanism of the elastic oscillation effect on oil and water filtration is explained. It is shown that liberation of part of the dissolved gas from oil due to vibroseismic action may change phase permeabilities in the oil-water system.Notation m porosity - k absolute permeability - k_w, k_o, k_g phase permeabilities of water, oil, gas, respectively - density - viscosity - s saturation - p pressure - P₀ hydrostatic pressure - p₀ pressure oscillation amplitude - x distance - P_sat saturation pressure - z mass fraction of the dissolved gas in oil - R(p) gas solubility in oil (maximum amount of gas dissolved in 1 kg of oil at a given pressure) - v set of a governing vibration parameters - q fluid flowrate - t time - R₀ initial radius of a gas bubble - D diffusion coefficient - ₀ gas concentration in the fluid far from a bubble - W vibrosource power. Indices w, o, g refer to the water, oil gas parameters, respectively A. P. Krylov All-Union Oil and Gas Scientific-Research Institute, Moscow. Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 64, No. 4, pp. 443–448, April, 1993.     

Theory of orbital dynamics of the A phase of superfluid 3He. II. Orbital hydrodynamic equations

Orbital hydrodynamic equations in ³He-A are derived microscopically in the hydrodynamic regime near the transition temperature. Transport coefficients as well as reactive coefficients are evaluated as rigorously as possible. The expression for the time derivative of the phase of the order parameter is shown to contain l · rot _n with the Yosida function as a coefficient. It is shown that when the supercurrent is given by the usual definition which includes only the first-order space derivative of the order parameter, the stress tensor becomes antisymmetric and there is an additional contribution to the local angular momentum density of dynamical origin. The stress tensor can be made symmetric by changing the definition of the supercurrent.     

Calculating the hydraulic resistance of foam flows in tubes

Formulas are derived for calculating the hydraulic resistance factor of a foam flow for isothermal flow in a tube with allowance for compressibility, biphasality, and a change in the structure of the foam during its movement.Notation p pressure in a cross section of the tube - p total pressure drop on a section of the tube - p_fr pressure drop due to friction on a section of the tube - u mean flow rate - specific gravity - K expansion ratio - T flow temperature - R universal gas constant - G weight flow rate - weight gas flow rate - ¯d weighted mean diameter of bubble - surface tension coefficient - D tube diameter - L length of section of tube - F cross-sectional area of tube Indices liquid phase - 0 atmospheric conditions for p=9.8·10⁴ Pa Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 39, No. 4, pp. 624–628, October, 1980.     

Heat transport by residual gases in multilayer vacuum insulation

The results of an experimental investigation of residual gas heat-transfer in multilayer vacuum insulation are reported. The thermal paradox observed when the cold-wall temperature changes from 77 to 20.4° K is explained. Graphs of the variation of the residual gas pressure in the insulation layers are given and the components of the total heat fluxradiative and residual gas-are determined.     

Collective Excitations of a One-Dimensional Fermi Gas Under Harmonic Confinement

We study the spectrum of collective excitations of a spin-polarized Fermi gas confined in a one-dimensional harmonic trap at zero temperature. In the collisionless regime we evaluate exactly the dynamic structure factor, while in the collisional regime we solve analytically the linearized equations of hydrodynamics in the Thomas-Fermi approximation. We also verify the validity of the Thomas-Fermi theory by solving numerically a time-dependent nonlinear Schroedinger equation with a fifth-order interaction term. We find that in both the collisionless and the collisional regime the excitation frequencies of the Fermi gas are multiples of the trap frequency, analogously to the case of the one-dimensional homogeneous Fermi fluid where the velocities of zero and first sound coincide. Due to boson-fermion dynamical mapping our results for the spectrum apply as well to a one-dimensional Bose gas with hard-core point-like interactions (Tonks gas).     

Dynamics of Trapped Bose Gases at Finite Temperatures

Starting from an approximate microscopic model of a trapped Bose-condensed gas at finite temperatures, we derive an equation of motion for the condensate wavefunction and a quantum kinetic equation for the distribution function for the excited atoms. The kinetic equation is a generalization of our earlier work in that collisions between the condensate and non-condensate (C ₁₂ ) are now included, in addition to collisions between the excited atoms as described by the Uehling–Uhlenbeck (C ₂₂ ) collision integral. The continuity equation for the local condensate density contains a source term ₁₂ which is related to the C ₁₂ collision term. If we assume that the C ₂₂ collision rate is sufficiently rapid to ensure that the non-condensate distribution function can be approximated by a local equilibrium Bose distribution, the kinetic equation can be used to derive hydrodynamic equations for the non-condensate. The ₁₂ source terms appearing in these equations play a key role in describing the equilibration of the local chemical potentials associated with the condensate and non-condensate components. We give a detailed study of these hydrodynamic equations and show how the Landau two-fluid equations emerge in the frequency domain is a characteristic relaxation time associated with C ₁₂ collisions. More generally, the lack of complete local equilibrium between the condensate and non-condensate is shown to give rise to a new relaxational mode which is associated with the exchange of atoms between the two components. This new mode provides an additional source of damping in the hydrodynamic regime. Our equations are consistent with the generalized Kohn theorem for the center of mass motion of the trapped gas even in the presence of collisions. Finally, we formulate a variational solution of the equations which provides a very convenient and physical way of estimating normal mode frequencies. In particular, we use relatively simple trial functions within this approach to work out some of the monopole, dipole and quadrupole oscillations for an isotropic trap.     

Analysis of the Propagation Conditions and Reaction Mechanisms During TiC Combustion Synthesis Performed Under High Isostatic Pressure

Titanium carbide was synthesized from self-propagating high temperature synthesis (SHS) performed under isostatic gas pressure ranging from 70 bars up to 700 bars. Propagation conditions of the combustion reaction have been studied as a function of gas pressure for C reactant of different diameters (20 m and 7 m). For coarse particles, the reaction stops upon increasing pressure, while for fine particles, reaction self-propagates up to 700 bars. It is shown that this change in propagation conditions can be explained by considering both thermal and kinetic effects. Finally, TiC formation mechanisms are discussed for SHS performed under high isostatic pressure.     

The Runaway of Electrons and the Formation of Beams in Glow Discharges

Analytical methods are used to obtain the criterion defining the boundary between the beam and hydrodynamic modes of motion of electrons in uniform and nonuniform electric fields for Townsend and high-voltage glow discharges. The beam approximation is used to study the electron energy distribution function in view of electrons being produced in gas. The hydrodynamic approximation is used to obtain the criterion which characterizes the runaway of electrons and the criterion of transition to the beam mode of motion. It is demonstrated that the curve of discharge ignition on the U(pd) diagram differs significantly from the boundary line between the beam and hydrodynamic modes of motion of electrons.