On the mechanism of self-oscillations of a supersonic radial jet exhausting into an ambient space

Results of an experimental study and numerical simulation of self-oscillations of a supersonic radial jet exhausting from a plane radial nozzle into an ambient space are reported. It is demonstrated that flexural oscillations develop in the jet, leading to its destruction. Feedback ensured by acoustic waves in the gas surrounding the supersonic jet is found to play a key role in the emergence of self-oscillations.     

Density distribution in a supersonic jet exhausting into vacuum from a nozzle with an inclined exit

Fairly effective methods have been developed to calculate axisymmetric jets of an inviscid perfect gas exhausting into vacuum, and approximations have also been obtained for the density field in such jets at large distances from the nozzle exit (see, for example, [1—3] and the bibliography in them). If the plane of the exit of the nozzle is not perpendicular to its axis, the flow in the jet is three dimensional. In a number of cases one can take into account the influence of the inclined exit with sufficient accuracy by a correction in the density distribution. An expression for such correction is given in the present paper. It is obtained on the basis of earlier calculations of the author [4], in which flow from a source was specified at the nozzle exit.     

Flow structure at the initial section of a supersonic jet exhausting from a nozzle with chevrons

The spatial structure of the flow in a supersonic underexpanded jet exhausting from a convergent nozzle with vortex generators (chevrons) at the exit is experimentally studied. Exhaustion of a supersonic underexpanded jet from a nozzle with chevrons at the nozzle exit is numerically simulated with the use of the Fluent commercial software package. The experimental and numerical data are demonstrated to be in reasonable agreement. The influence of chevrons on the process of gas mixing is estimated.     

Thermal multipoles for a jet in ambient spathermal multipoles for a jet in ambient space

A general solution of the thermal problem for a non-self-similar axisymmetric jet is determined on the basis of the multiple approach developed for problems of non-self-similar jets in ambient space [1, 2], and several problems of convective heat-transfer in simply- or doubly-connected domains are solved. The advantage of expanding the solution of the convective heat conduction equation in eigenfunctions of the problem is demonstrated. As an illustration, the solutions for a thermal dipole and quadrupole and for a jet flow in a heated tube are presented. The corresponding solutions are also obtained for a turbulent jet in ambient space. The most favorable heat-exchange regime for a jet in a heated tube is predicted on the basis of the particular behavior of the eigenfunctions of the thermal problem.Novosibirsk. Translated from Izvestiya Rossiiskoi Akademii Nauk, Mekhanika Zhidkosti i Gaza, No. 1, pp. 40–46, January–February, 1996.     

Density field of a jet of viscous gas flowing from a conical nozzle into a vacuum

An approximate dependence for calculating the density field in a jet of viscous gas flowing from a conical nozzle into a vacuum is proposed on the basis of an experimental investigation and an analysis of the results of a numerical solution of the complete system of Navier-Stokes equations.Translated from Izvestiya Akademii Nauk SSSR, Mekhanika Zhidkosti i Gaza, No. 3, pp. 25–30, May–June, 1986.     

Calculation of a supersonic gas jet exhausting into vacuum from a nozzle with an inclined exit

A study is made of the problem of supersonic exhausting of ideal gas into vacuum from a conical nozzle with inclined exit. The solution is sought in a region including part of the flow where the projection of the velocity vector of the gas onto the nozzle axis can be less than the local velocity of sound and take negative values.Translated from Izvestiya Akademii Nauk SSSR, Mekhanika Zhidkosti i Gaza, No. 3, pp. 185–186, May–June, 1982.     

Flow and acoustic features of a supersonic tapered nozzle

The acoustic and flow characteristics of a supersonic tapered jet were measured for free and shrouded flow configurations. Measurements were performed for a full range of pressure ratios including over- and underexpanded and design conditions. The supersonic tapered jet is issued from a converging-diverging nozzle with a 31 rectangular slotted throat and a conical diverging section leading to a circular exit. The jet was compared to circular and rectangular supersonic jets operating at identical conditions. The distinct feature of the jet is the absence of screech tones in the entire range of operation. Its near-field pressure fluctuations have a wide band spectrum in the entire range of measurements, for Mach numbers of 1 to 2.5, for over- and underexpanded conditions. The free jet's spreading rate is nearly constant and similar to the rectangular jet, and in a shroud, the pressure drop it is inducing is linearly proportional to the primary jet Mach number. This behavior persisted in high adverse pressure gradients at overexpanded conditions, and with nozzle divergence angles of up to 35°, no inside flow separation was observed.     

Discharge of a supersonic jet from a nozzle with an inclined rim

The main results of a numerical study of the effect of the angle of the rim of a nozzle on the shape of the jet boundary and of the free shock and on the distribution of parameters in a three-dimensional underexpanded jet are presented. A noncentered second-order difference scheme is used to solve the gasdynamic equations for an inviscid perfect gas. Conditions are established for which the three-dimensional jet is observed to coincide partially in the radial planes and the corresponding planes of axisymmetric jets.Translated from Izvestiya Akademii Nauk SSSR, Mekhanika Zhidkosti i Gaza, No. 4, pp. 105–110, July–August, 1977.In conclusion, the authors thank G. I. Petrov and his colleagues for detailed discussion of the results of the investigation reported here.     

Calculation of a supersonic overexpanded jet of an ideal gas issuing into an ambient transonic flow

The results of a numerical investigation of the exhaust of an inviscid axisymmetric jet into an ambient transonic flow in the overexpansion mode are presented. The steady-state flow pattern is obtained during a buildup process by integration of the nonsteady-state equations of gasdynamics using Godunov's finite-difference method.Translated from Izvestiya Akademii Nauk SSSR, Mekhanika Zhidkosti i Gaza, No. 4, pp. 155–158, July–August, 1976.The authors are indebted to A. N. Kraiko and M. Ya. Ivanov for useful discussions and their interest in the work.     

Flow around a sphere by a two-phase supersonic jet

Results are presented of a calculation of the flow around a sphere of a two-phase supersonic jet, discharging into a vacuum. Calculations were performed by the determination method with use of a difference grid constructed on the basis of characteristic ratios [1], The parameters of the unperturbed jet were determined with the two-velocity and two-temperature model of mutually penetrating flows of continuous media (gas and particles) [2, 3] by the network method [4]. In calculating the flow around the sphere, as in [5–7], it was assumed that the particles do not affect the gas flow in the shock layer. An analysis of the effect of particles on gasdynamic parameters in a shock layer was performed in [8].Translated from Izvestiya Akademii Nauk SSSR, Mekhanika Zhidkosti i Gaza, No. 6, pp. 171–176, November–December, 1978.The authors are grateful to A. N. Nikulin for providing the program for calculation of flow about a blunt body by a uniform supersonic flow.     

Structure of a supersonic jet with varied geometry of the nozzle entrance

The structure of a supersonic underexpanded lowpressureratio jet exhausted from a nozzle with variable geometry of the entrance section is experimentally studied. Total pressure distributions in the initial cross sections of the examined jets are obtained. Based on these distributions, the coordinates of the mixingregion boundaries are found. The curvature of streamlines in the mixing layer within the first two barrels of an underexpanded jet is determined. A dependence generalizing the measurement results on the curvature of streamlines in the first barrel of a weakly underexpanded jet is obtained in dimensionless coordinates.     

Vibrations of a fan jet in running a supersonic jet into a notched obstacle

Some kinds of vibrations of a fan jet are described. A physical model of one kind of self-excited vibrations of the fan jet is formulated. The formulas to calculate the frequencies of self-excited vibrations are given. Translated from Prikladnaya Mekhanika i Tekhnicheskaya Fizika, Vol. 40, No. 4, pp. 118–124, July–August, 1999.     

Flow regimes formed by a counterflow jet in a supersonic flow

Results on the effect of the dynamic pressure, Mach number, and temperature of a jet injected from a body upstream in a free supersonic flow on the formation of flow regimes are presented. Flow regimes that ensure the greatest decrease in the drag of the body are given, the mechanism of formation of the LPM flow structure is described, and an approximate criterion is found, which allows determination of the range of existence of various modes of jet penetration into the flow.     

Collision of supersonic flows in vacuum and ambient space

Based on numerical Monte Carlo simulation, the collision of plane-parallel supersonic flows in vacuum and ambient space is studied. The study of the transonic zone of a plane source instantaneously switched on in vacuum made it possible to establish the regular features of the flow parameters in the critical cross section and the validity of using gas-dynamic dependences obtained in the continuum approach for simulating gas exhaustion. Evolution of the structure of a compressed shock layer arising in the region of flow collision is studied. It is found that a collision of flows in the ambient space leads to a more significant increase in temperature in the compressed layer than in the case of a collision in vacuum. Kutateladze Institute of Thermal Physics, Siberian Division, Russian Academy of Sciences, Novosibirsk 630090. Translated from Prikladnaya Mekhanika i Tekhnicheskaya Fizika, Vol. 40, No. 4, pp. 44–50, July–August, 1999.     

Emission of a discrete tone by a supersonic jet flowing out of a conical nozzle

The article gives the results of an experimental investigation of the emission of a discrete tone by supersonic jets flowing out of conical supersonic nozzles. It is shown that a change in the aperture angle of the nozzle, the other parameters remaining unchanged, has a considerable effect on the structure of the flow in the initial section of the jet, which leads to a change in the frequency of the discrete tone and in the range of the degree of the rated capacity with which it arises.