Propagation of disturbances in supersonic vibrationally nonequilibrium gas flows

The propagation of finite disturbances in nonequilibrium supersonic gas flows is investigated, and the effect of entropy and acoustic disturbances on the inversion characteristics of the medium is analyzed.Translated from Izvestiya Akademii Nauk SSSR, Mekhanika Zhidkosti i Gaza, No. 2, pp. 128–134, March–April, 1990.     

Effect of the acoustic regularization of initial perturbations on the development of ordered structures

Mechanisms are considered by which acoustic oscillations influence the structure of subsonic shear flows. Analysis of the experimental data [1–7] confirms the assumption made in [6] that the regularization of initial perturbations, which causes a higher degree of ordering and an increase in the life of vortices formed because of the development of instability waves or interaction of acoustic oscillations with the edge of the nozzle, is one of the mechanisms by which acoustics influences various shear flows. Photographs are given which show the regularizing effect of acoustics on the development of vortices in the wake behind the edge.Translated from Izvestiya Akademii Nauk SSSR, Mekhanika Zhidkosti i Gaza, No. 1, pp. 171–174, January–February, 1986.     

Application of the ultrasonic technique and high-speed filming for the study of the structure of air–water bubbly flows

Multiphase flows are very common in industry, oftentimes involving very harsh environments and fluids. Accordingly, there is a need to determine the dispersed phase holdup using noninvasive fast responding techniques; besides, knowledge of the flow structure is essential for the assessment of the transport processes involved. The ultrasonic technique fulfills these requirements and could have the capability to provide the information required. In this paper, the potential of the ultrasonic technique for application to two-phase flows was investigated by checking acoustic attenuation data against experimental data on the void fraction and flow topology of vertical, upward, air–water bubbly flows in the zero to 15% void fraction range. The ultrasonic apparatus consisted of one emitter/receiver transducer and three other receivers at different positions along the pipe circumference; simultaneous high-speed motion pictures of the flow patterns were made at 250 and 1000 fps. The attenuation data for all sensors exhibited a systematic interrelated behavior with void fraction, thereby testifying to the capability of the ultrasonic technique to measure the dispersed phase holdup. From the motion pictures, basic gas phase structures and different flows patterns were identified that corroborated several features of the acoustic attenuation data. Finally, the acoustic wave transit time was also investigated as a function of void fraction.     

Calculations of two-dimensional nonstationary flows of a viscous gas blown into a short cylindrical channel

An investigation was made of the nonstationary problem of laminar axisymmetric flow of a viscous gas in a short cylindrical channel at one end of which the gas is blown in at an increasing rate with parabolic flow-rate profile; the other end is open. The problem was solved numerically on the basis of the complete two-dimensional system of Navier-Stokes equations for an ideal gas at the characteristic numbers M = 0.2, Pr = 1, Re = 20, 200, 2000. An investigation was made into the nonlinear process of pulsed excitation of longitudinal acoustic oscillations, which for Re = 2 000 give rise to separation flows. In this case, secondary oscillatory phenomena are observed in the separated viscous shear layers. The damping of the oscillations is treated on the basis of the proposed nonlinear model of the sound absorbing end wall.Translated from Izvestiya Akademii Nauk SSSR, Mekhanika Zhidkosti i Gaza, No. I, pp. 9–17, January–February, 1979.I thank G. I. Petrov for his interest in the work and valuable comments.     

Heat transfer in a gas in the presence of acoustic turbulence

An equation for the average internal energy of a gas in a field of acoustic turbulence is obtained by the method of perturbation theory. It is shown that, in addition to the characteristic increase in the coefficient of thermal conductivity, acoustic turbulence leads to heating of the gas through compressibility and heat-conduction effects. At large Mach and Péelet numbers the heating has an exponential character with time. An expression determining the absorption of acoustic vibrations in a gas is obtained.Translated from Izvestiya Akademii Nauk SSSR, Mekhanika Zhidkosti i Gasa, No. 1, pp. 183–187, January–February, 1978.     

Modeling and computation of cavitation in vortical flow

The paper presents an investigation of Euler–Lagrangian methods for cavitating two-phase flows. The Euler–Euler methods, widely used for simulations of cavitating flows in ship technology, perform well in regions of moderate flow changes but fail in zones of strong, vortical flow. Reasons are the strong approximations of cavitation models in the Euler concept. Alternatively, Euler–Lagrangian concepts enable more detailed formulations for transport, dynamics and acoustic of discrete vapor bubbles. Test calculations are performed to study the influence of different parameters in the equations of motion and in the Rayleigh–Plesset equation for bubble dynamics. Results confirm that only Lagrangian models are able to describe correctly the bubble behavior in vortices, while Eulerian results deviate strongly. Lagrangian formulations enable additionally the determination of acoustic pressure of cavitation noise. Two-way coupling between the phases is required for large regions of the vapor phase. A new coupling concept between continuous fluid flow and discrete bubble phase is developed and demonstrated for flow through a nozzle. However, the iterative coupling between the phases via volume fractions is computationally expensive and should therefore be applied only in regions where Eulerian treatment fails. A corresponding local concept for combination with an Euler–Euler method is outlined and is in progress.     

Modeling of an intense-noise-generating flow

The possibility of creating a model flow generating noise spectra characteristic of an internal combustion engine exhaust without combustion processes is demonstrated. Some data on the spectra of acoustic disturbances produced by changes introduced into the gas flow behind the cylinder exit are presented. Possible ways of acting on the large-scale hydrodynamic structures in the flow in order to attenuate the induced acoustic oscillations are discussed.Moscow. Translated from Izvestiya Rossiiskoi Akademii Nauk, Mekhanika Zhidkosti i Gaza, No. 2, pp. 83–91, March–April, 1995.     

Weakly rarefied gas flows between nonuniformly heated parallel plates

The aim of this research is to establish the validity of the predictions of the theory of slow nonisothermal flows, to study the limits of applicability (with respect to the Knudsen number) of the conclusions reached and to determine the effect of the Knudsen layers on these flows on the basis of a numerical investigation of slow nonisothermal weakly rarefied gas flow in a plane infinite channel with weakly nonequilibrium heating of the walls and a finite wall temperature difference. The gas flow is described by a relaxation transport equation. The results obtained show how quickly, as the Knudsen number decreases, the solutions of the transport equation outside the Knudsen layers tend to the solution of the equations of gas dynamics of slow nonisothermal flows (and not to the solution of the Navier-Stokes equations).Translated from Izvestiya Akademii Nauk SSSR, Mekhanika Zhidkosti i Gaza, No. 1, pp. 115–121, January–February, 1988.     

The reflection of a plane shock wave from a body with groove

When a plane shock wave impinges on bodies with grooves and when a supersonic stream of gas flows past such bodies a complicated flow pattern develops. In a number of cases oscillations of the bow wave [1–3] and an anomalous heating of the gas in the groove [4–6] have been observed. Unsteady reflection of shock waves from bodies with grooves and the processes occurring inside the grooves have been investigated comparatively little.Translated from Izvestiya Akademii Nauk SSSR, Hekhanika Zhidkosti 1 Gaza, No. 5, pp. 180–186, September–October, 1935.The authors wish to thank V. I. Ivanov for carrying out the calculations.     

Nonlinear analysis of the flow initiated by the sudden motion of a wedge

Certain self-similar problems involving the sudden motion of a wedge which were treated in the linear approximation in [1–3] are studied by the method of matched asymptotic expansions. The nature of the wave boundary of the perturbed region is determined. Second-approximation solutions are constructed which describe flows behind weak shock fronts propagating in a stationary gas and behind fronts of weak discontinuity lines propagating by known uniform flows. A boundary-value problem is formulated whose solution describes, in first approximation, flows in the neighborhoods of points of interaction of the fronts. The existence of similarity rules of flows in these nieghborhoods is estimated. An approximate solution of the problems is given.Translated from Zhurnal Prikladnoi Mekhaniki i Tekhnicheskoi Fiziki, No. 3, pp. 37–47, May–June, 1976.     

Escape of a turbulent jet under the effect of acoustic perturbations

Results are presented of experimental investigations of the local effect of acoustic oscillations of different frequency and constant intensity on the root part of a nonisothermal axisymmetric subsonic turbulent jet escaping from a gas jet atomizer at a different velocity in the S = 0.053–3.84 range of Strouhaille numbers. Data have been obtained indicating the presence of unstable escape modes of a subsonic turbulent jet in an acoustic field; experimental dependences are presented of the relative aperture of the turbulent jet flowing in an acoustic field as a function of various parameters.Translated from Zhurnal Prikladnoi Mekhaniki i Tekhnicheskoi Fiziki, No. 1, pp. 58–62, January–February, 1972.The author is grateful to A. S. Ginevskii and B. S. Burikov for discussing the results of this paper, and also to A. S. Modnov and R. A. Arkhipova for assistance in conducting and processing the experiments.     

Some one-dimensional unsteady adiabatic gas flows with plane symmetry

A method for the approximate analytic investigation of one-dimensional adiabatic gas flows in the form of arbitrary small perturbations of a simple wave is proposed. A class of exact solutions which, in particular, describes the flows arising from the short intense impact of a piston moving under gas pressure is obtained.Translated from Izvestiya Akademii Nauk SSSR, Mekhanika Zhidkosti i Gaza, No. 5, pp. 96–104, September–October, 1986.     

Gas solubility effects associated with the propagation of small perturbations in bubbly mixtures

The effect of gas solubility on the oscillation characteristics of bubbles in an acoustic field, the propagation and damping of perturbations in bubbly mixtures and, moreover, the stability of such media is analyzed.Translated from Izvestiya Akademii Nauk SSSR, Mekhanika Zhidkosti i Gaza, No. 4, pp. 70–77, July–August, 1988.     

Measurement of translational temperature in low-density jets

A technique and method for measuring the velocity-distribution function of the atoms in rarefied gas flows are described. Some results obtained with flows of binary gas mixtures behind a sonic nozzle are presented. The temperature of the light component (helium) is determined from the half width of the distribution function. Incomplete restoration of the helium temperature occurs in the Mach disk. This effect is examined in relation to concentration. A qualitative explanation is proposed for the effect in question.Translated from Zhurnal Prikladnoi Mekhaniki i Tekhnicheskoi Fiziki, No. 1, pp. 30–34, January–February, 1973.     

Detonation Wave Propagation in Rotational Gas Flows

This paper studies the propagation of detonation and shock waves in vortex gas flows, in which the initial pressure, density, and velocity are generally functions of the coordinate — the distance from the symmetry axis. Rotational axisymmetric flow having a transverse velocity component in addition to a nonuniform longitudinal velocity is considered. The possibility of propagation of Chapman–Jouguet detonation waves in rotating flows is analyzed. A necessary conditions for the existence of a Chapman–Jouguet wave is obtained.     

High-velocity cumulative gas jets

The author examines the theory of the cumulation effect [1] in axisymmetric inviscid perfect gas flows and the possibility of creating cumulative gas jets with velocities considerably in excess of the speed of sound.Translated from Izvestiya Akademii Nauk SSSR, Mekhanika Zhidkosti i Gaza, No. 4, pp. 148–152, July–August, 1989.     

Similarity of flows in strongly underexpanded jets of viscous gas

The fulfillment of the conditions formulated in [1] for the similarity of flows in strongly under-expanded jets of a viscous, thermodynamically ideal gas is studied. The limits of applicability of these conditions are established on the basis of exact solutions of the one-dimensional Navier —Stokes equations and experimental investigations.Translated from Izvestiya Akademii Nauk SSSR, Mekhanika zhidkosti i Gaza, No. 6, pp. 117–125, November–December, 1978.     

A plane-parallel nonstationary motion of gas

A solution is found to the system of equations that describe plane-parallel nonstationary irrotational flows of an ideal gas under the condition that the velocity components of the gas depend on the polar angle and the time t.Translated from Izvestiya Akademii Nauk SSSR, Mekhanika Shidkosti i Gaza, No. 6, pp. 156–157, November–December, 1979.     

Excitation of unstable modes in a supersonic boundary layer by acoustic waves

The acoustic excitation of the first and second boundary layer modes in the neighborhood of the sharp leading edge of a plate in a supersonic gas flow is analyzed.Translated from Izvestiya Akademii Nauk SSSR, Mekhanika Zhidkosti i Gaza, No. 4, pp. 67–74, July–August, 1991.     

Nonequilibrium condensation of metal vapor mixed with an inert gas in nozzle expansion in cluster beam generators

A closed mathematical model of flows of a mixture consisting of a homogeneously condensible vapor and an inert gas is described. This model is a further development of the pure metal vapor condensation model [1 – 4] and, as distinct from the latter, makes it possible to take into account the effect of molecules of inert gas not only on the thermodynamics of the mixture but on the detailed kinetics of the processes of the cluster formation and breakdown. The results of numerical calculations of the formation of iron and silver clusters in experimental installations are presented.Translated from Izvestiya Rossiiskoi Akademii Nauk, Mekhanika Zhidkosti i Gaza, No. 3, pp. 80–91, May–June, 1995.