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.     

Shear and necking instabilities in nonlinear elasticity

This paper examines the behavior of a class of nonlinearly elastic rods under tension. These rods can suffer longitudinal extension, transverse contraction, shear, and flexure. The deformation is governed by an eighth order, quasilinear system of ordinary differential equations. A convergent perturbation process shows that there is a very rich collection of solutions that bifurcate from the trivial affine configuration. Global results are obtained for hyperelastic rods. These solutions describe instabilities of the shear and necking type and can exhibit hysteresis.

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Résumé On considère le comportement d'une classe de poutres nonlinéairement élastiques en état de tension. Ces poutres peuvent souffrir une extension longitudinale, une contraction transversale, un cisaillement et une fiexion. La déformation est gouvernée par un système quasi-linéaire d'équations différentielles ordinaires du huitième ordre. Un procès convergeant de perturbations montre qu'il y a une collection très riche de solutions qui bifurquent de la configuration banale affine. Dans le cas hypérélastique on obtient des résultats globaux. On montre que ces solutions décrivent des instabilités du type de cisaillement et d'étranglement et peuvent exhiber une hystérésis.

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The research of the first author was supported by National Science Foundation Grant MPS 73-08587 A02. Some of the results reported here were obtained by the second author in his master's thesis.     

Visual observations of supersonic transverse jets

We present experimental results on penetration of round sonic and supersonic jets normal to a supersonic cross flow. It is found that penetration is strongly dependent on momentum ratio, weakly dependent on free-stream Mach number, and practically independent of jet Mach number, pressure ratio, and density ratio. The overall scaling of penetration is not very different from that established for subsonic jets. The flow is very unsteady, with propagating pressure waves seen emanating from the orifice of helium jets.     

Buoyancy effects on flow transition in low-density inertial gas jets

Effects of buoyancy on transition from laminar to turbulent flow are presented for a momentum-dominated helium jet injected into ambient air. The buoyancy was varied in a 2.2 s drop tower facility without affecting the remaining operating parameters. The jet flow in Earth gravity and microgravity was visualized using the rainbow schlieren deflectometry apparatus. Results show significant changes in the flow structure and transition behavior with change of buoyancy.     

Structure of high-pressure low-density jets beyond a supersonic nozzle

The results are presented on an experimental study of the structure of high-pressure low-density jets beyond a supersonic nozzle when the gas escapes into a quiescent medium.     

High-temperature jets of low-density argon beyond a sonic nozzle

The gasdynamic structure of rarefied argon jets is studied in the range of stagnation temperatures of from 290 to 5200 °K using the electron-x-ray method. The effect of the temperature factor on different zones of the jet is shown and the reorganization of the flow pattern with a change in the mode of flow from continuous to free-molecular is analyzed.     

Supersonic flow past a body with transverse jets

The results of an experimental study of the flow past a body with transverse jets are presented. The gas jets flowed out simultaneously from several nozzles arranged on the body's lateral surface. Various flow regimes were considered to such parameters as the relative jet momentum, the angle of incidence, etc. The experimental results were generalized on the basis of an approximate similarity law.Moscow. Translated from Izvestiya Rossiiskoi Akademii Nauk, Mekhanika Zhidkosti i Gaza, No. 4, pp. 75–80, July–August, 1995.     

Some features of body-flow interaction in the presence of transverse jets

A technique for studying the effectiveness of bow thrusters of the "propeller in a tunnel" type is proposed, validated, and checked by testing models in a hydrodynamic tunnel. The interaction of the thruster generated jets with the flow near a ship hull model is studied at low flow velocities. The dependence of the lateral force on the shape of the initial cross section and the relative velocity of the jet outflowing from the thruster tunnel is studied. A strong dependence of the lateral force on the Reynolds number based on the free-stream velocity and the characteristic dimension of the initial jet section is revealed on the range of relative jet velocities investigated. The case of cavitation collision of the thruster jet with the external flow, when a considerable amount of gas is fed into the near wake zone downstream of the jet, is also examined. Moscow. Translated from Izvestiya Rossiiskoi Akademii Nauk, Mekhanika Zhidkosti i Gaza, No. 3, pp. 18–24, May–June, 1998. A considerable part of this research was carried out in connection with interest demonstrated by certain shipbuilding industry organizations and with financial support from the Russian Foundation for Basic Research (project No. 95-01-00056).     

Penetration height correlations for non-aerated and aerated transverse liquid jets in supersonic cross flow

Experimental results on the mixing of non-aerated and aerated transverse liquid jet in supersonic cross flow (M = 1.5) are presented in this paper. The goal of this study is to investigate the effect of the gas/liquid mass ratio on the penetration and atomization of an aerated liquid jet in high speed cross flow and to develop correlations for the penetration heights. High speed imaging system was used in this study for the visualization of the injection of aerated liquid jet. The results show the effect of jet/cross flow momentum flux ratio, the gas/liquid mass ratio and the Ohnesorge number on the penetration of aerated liquid jet in supersonic cross-flow. New correlations of the spray penetration height for the non-aerated liquid jet (GLR = 0) and the net gain in spray penetration height for the aerated liquid jet (GLR > 0) are presented.     

Flow pattern in the vicinity of an annular system of transverse jets in a supersonic stream

The pattern of the flow in the vicinity of an annular system of jets exiting into a supersonic stream from orifices on a cylindrical surface with a turbulent boundary layer is experimentally investigated Four typical flow regimes are recorded The effect of the jet number and the nozzle-to-outer pressure ratio on the extent of the separation zone and its structure ahead of and behind the jet system is determined Moscow. Translated from Izvestiya Rossiiskoi Akademii Nauk, Mekhanika Zhidkosti i Gaza, No. 1, pp. 21–27, January–February, 1999.     

Shear layer behavior resulting from shock wave diffraction

All previous studies on shock wave diffraction in shock tubes have spatial and temporal limitations due to the size of the test sections. These limitations result from either the reflection of the expansion wave, generated at the corner, from the top wall and/or of the reflection of the incident diffracted shock from the bottom wall of the test section passing back through the region of interest. This has limited the study of the evolution of the shear layer and its associated vortex, which forms a relatively small region of the flow behind the shock with an extent of only a few centimeters, and yet is a region of significant interest. A special shock tube is used in the current tests which allow evolution of the flow to be examined at a scale about an order of magnitude larger than in previously published results, with shear layer lengths of up to 250 mm being achieved without interference from adjacent walls. Tests are presented for incident shock wave Mach numbers of nominally 1.3–1.5. Studies have been undertaken with wall angles of 10, 20, 30 and 90°. Significant changes are noted as the spatial and temporal scale of the experiment increases. For a given wall angle, the flow behind the incident shock is not self-similar as is usually assumed. Both shear layer instability and the development of turbulent patches become evident, neither of which have been noted in previous tests.     

Experimental investigation of instabilities in flow through a long square channel rotating about the transverse axis

The results of an experimental investigation of bifurcation phenomena in a laminar flow through a rotating square channel approximately 50 channel widths long are presented. A comparison with known results of the numerical modeling of bifurcations of developed steady-state flow is carried out. A map of the steady and unsteady flow regimes is plotted. The effect of artificially generated input perturbations on the conditions of onset of longitudinally oriented vortex structures in the neighborhood of the elevated-pressure side of channels of lesser length is investigated.St. Petersburg. Translated from Izvestiya Rossiiskoi Akademii Nauk, Mekhanika Zhidkosti i Gaza, No. 2, pp. 87–93, March–April, 1996.     

Supersonic flow past a cylindrical body with transverse jets at large angles of attack

Supersonic flow past a cylindrical body with a system of transverse jets ejected from its surface at angles of attack α=60–120^o is characterized by a complicated gasdynamic flow pattern [1]. The body surface is affected by both the oncoming flow and the ejected jets which shield a portion of the surface from the external flow. This results in considerable transverse and longitudinal pressure gradients appearing on the body surface. The experimental pressure distributions over a cylindrical model with four transverse jets at a Mach number M=4 and α=60°, 90°, and 120° make it possible to study the specific features of the flowfield and derive correlations for the "jet obstacle" dimensions. Moscow. Translated from Izvestiya Rossiiskoi Akademii Nauk, Mekhanika Zhidkosti i Gaza, No. 1, pp. 179–183, January–February, 1998.     

Interaction between a shock wave and a longitudinal low-density gas layer

The problem of the interaction between a shock wave and a semi-infinite longitudinal plane layer or a cylindrical channel of finite thickness filled with a low-density gas is studied on the basis the Euler equations. The flow gasdynamics, including qualitatively new, regular and irregular, interaction regimes, are described. New gasdynamic flow elements, such as high-pressure jets with an internal wave structure and layered vortices, are found to exist. It is revealed that the gasdynamic precursor growth is decelerated at long time intervals, due to the flow chocking effect and the vorticity development behind its front.     

Shear layer instability and acoustic interaction in solid propellant rocket motors

Segmentation of solid propellant rocket motors has been demonstrated to be a source of unpredicted and undesirable pressure and thrust oscillations. Surface discontinuities are the primary cause of these vortex-shedding-driven oscillations, which result from a strong coupling between the shear layer instability and the acoustic motion in the chamber. The analysis of an axisymmetric geometry corresponding to a {1\over 15} subscale P230 motor of the Ariane 5 rocket is numerically computed. With a suitable mesh for the viscosity value studied, the aeroacoustics in the chamber is fully described. A coupling between the hydrodynamic instability and the organ-pipe acoustic mode is clearly demonstrated. The mechanism for frequency selection is discussed. © 1997 John Wiley & Sons, Ltd.     

Numerical study of spatial supersonic flow of a perfect gas with transverse injection of jets

Three-dimensional supersonic turbulent flow in the presence of symmetric transverse injection of round jets through slots in the walls is studied numerically. The simulation is based on Favre averaged Navier-Stokes equations solved using the Beam-Warming method. The influence of the ratio of the pressure in the jet to that in the flow (pressure ratio) on the spatial interaction of the injected jet with the oncoming flow is studied. Experimental pressure distributions on the wall near the jet approximated by curvilinear closed ellipses are reproduced numerically. The mechanism of the formation of two symmetric vortices in the mixing layer between the jet and the oncoming flow is studied. The results of the calculations are found to be in satisfactory agreement with the experimental dependence of the length of the separation zone on the pressure ratio of the jet to the flow.     

Numerical analysis of secondary instabilities of the incompressible boundary layer flow with suction

Based on the Euler–Maclaurin formula, a compact finite difference scheme is employed to solve a two-point boundary value problem for studying the secondary instabilities of the boundary layer flow. The parametric resonance of unstable waves is explored using the Floquet method. For both subharmonic and fundamental modes, two additional Fourier terms are added in the analysis, and the spatial growth rates are determined. The effect of suction mechanism on the secondary instability waves is also investigated. From numerical experiments, it is shown that the proposed numerical scheme is very promising. © 1998 John Wiley & Sons, Ltd.