Application of rainbow schlieren deflectometry for concentration measurements in an axisymmetric helium jet

 The rainbow schlieren deflectometry technique was used to measure oxygen concentrations in a laminar, isothermal helium jet discharged vertically into ambient air. The concentration distributions were inferred from the color schlieren image by taking into consideration the sampling interval and noise in measurements, especially near the jet center. Excellent quantitative agreement was reached between measurements from schlieren and a continuous sampling probe. This work demonstrates the capability of the schlieren technique for providing accurate, spatially-resolved, nonintrusive, full-field of view measurements of species concentration in an isothermal binary system. Because the basic quantity measured is the refractive index, the present schlieren technique can be extended for quantitative measurements of other scalar flow properties related to the refractive index. Received: 21 April 1997 / Accepted: 14 November 1997     

The Stress–Strain State of Geometrically and Physically Nonlinear Plates with One-Sided Corrosive Wear

A technique is proposed to investigate one-sided corrosive wear. The problem is solved with regard for geometric and physical nonlinearity. Two, Dolinskii's and Gutman's corrosion models are considered. The quasistatic problem is solved by the method of variational iterations, which reduce ordinary differential equations to a system of nonlinear equations with approximation o(h ²) to be solved by Newton's method. At each step, to allow for physical nonlinearity, the method of variable elastic parameters is used. Also a technique is developed to consider various boundary conditions and ⁱ(e ⁱ) diagrams. Specific numerical results are presented.     

Excitation of Van Kampen-case waves

The response of a fluid with a shear flow having a slightly curved profile to an external vertical impact force, harmonic with respect to the horizontal coordinate and concentrated in a narrow layer, is calculated. The cases of an ideal and a viscous fluid are considered.Translated from Izvestiya Akademii Nauk SSSR, Mekhanika Zhidkosti i Gaza, No. 1, pp. 115–119, January–February, 1987.The author wishes to thank G. I. Barenblatt, M. A. Mironov, and S. A. Rybak for useful discussions.     

Boundary kinetic effects in the problem of slow flow over an evaporating heat-conducting spherical particle

It is shown that for sufficiently large values of the thermal conductivity of the condensed phase' as compared with the thermal conductivity of the vapor (/' Kn) the effects associated with the presence of a Knudsen layer on the evaporating surface must be taken into account in order to obtain a solution of the problem of a spherical particle in a slow (Re, 1) continuum (Knudsen number Kn 1) flow of its own vapor. The drag is calculated for various types of boundary conditions on the particle surface.Translated from Izvestiya Akademii Nauk SSSR, Mekhanika Zhidkosti i Gaza, No. 2, pp. 134–139, March–April, 1987.In conclusion the authors wish to thank V. S. Galkin and M. N. Kogan for useful discussions.     

Stretching of squeezed liquid under the action of its own weight

The stretching of a liquid sample, squeezed out in the vertical direction from an aperture of an arbitrary form, is investigated. The problem of controlling the dimensions of the aperture or the rate of squeezing for obtaining samples of a given configuration is discussed.Translated from Izvestiya Akademii Nauk SSSR, Mekhanika Zhidkosti i Gaza, No. 5, pp. 10–14, September–October, 1975.     

Limiting energy characteristics of pulsed tea co2 lasers

The article presents the results of experimental studies on the determination of the characteristics of the process of absorption of large specific electrical energy densities in a wide range of pressures (0.1–0.5 atm CO₂?2N₂?0.5H₂). The presence of limitations (E₀/p ≥45 V/cm · torr, Q/p=? 1 J/cm³ · atm) which are responsible for the region of existence of a diffusional discharge was established, which made it possible to determine the relationship between the limiting electrical energy density which can be absorbed in the discharge, the initial parameters of the system, and the amount of radiated energy.     

Motion and filling of cavities in a boundless liquid and close to a plane

The motion of bubbles in liquids has been studied in many earlier papers [1–8]. In this paper methods of the projection type are applied to the problem of a cavity in an ideal, incompressible liquid in the absence of vortices. The collapse of a bubble having a finite initial velocity in a boundless liquid is considered; also considered is the collapse of a stationary bubble close to a solid wall. Using the small-parameter method the generation of a jet is examined analytically. A numerical computing method not involving small parameters is developed; it is based on calculating the projection by numerical computation of the corresponding integrals. The method combines economy and simplicity of application with a high accuracy in the region in which the representation of the velocity potential by a series of spherical functions remains effective.     

Oblique impacts of metallic plates in an elastic formulation

A previous work [1], in which the thickness of the colliding plates was assumed to be infinitely great and the velocity of the point of contact greater than the speed of sound c₁ in the matterial, represented one attempt to use linear elasticity theory in flash-welding problems. Oblique impact of metallic plates of finite thickness has been studied [2], the velocity V_c of the point of contact being assumed to be less than the velocity c₂ of transverse waves in the material. In this work, oblique impact of elastic plates with velocities V_c of the point of contact greater than the velocity of propagation c₂ of transverse waves will be considered.     

Diffusion in multicomponent gaseous mixtures in a model of local thermodynamic equilibrium

Diffusion of chemical elements into an ionized multicomponent gaseous mixture is considered in a model of local thermodynamic equilibrium. A linear dependence of the mass flows of chemical elements and the heat flow on the temperature gradient, mass fractions of the chemical elements, and the electric field is obtained. An example is given of a calculation of the effective diffusion coefficients for a hydrogen-helium mixture.     

Sound propagation and self-focusing in an inhomogeneous gas-liquid medium

The evolution of sound waves in a gas—liquid medium with an inhomogeneous distribution of the sound speed is considered in this paper on the basis of a nonlinear parabolic equation for the amplitude of the sound wave envelope. It is assumed that the nonlinearity due to the gas inclusions is much greater than the customary hydrodynamic nonlinearity. The influence of the inhomogeneity on the self-focusing of the sound is studied.Translated from Izvestiya Akademii Nauk SSSR, Mekhanika Zhidkosti i Gaza, No. 6, pp. 177–180, November–December, 1974.The author is grateful to I. R. Shreiber for discussion.