Equations and forms of motion of a jet flowing onto a liquid

A nonlinear theory is constructed for a thin jet of nonviscous, incompressible, weightless fluid flowing from a nozzle onto the surface of an immobile heavy liquid. The theory is asymptotically (over jet thickness) more accurate than that presented in [1]. Forms of the flow are studied as functions of nozzle, jet, and heavy liquid parameters.Translated from Izvestiya Akademii Nauk SSSR, Mekhanika Zhidkosti i Gaza, No. 6, pp. 20–28, November–December, 1976.     

Special characteristics of the propagation of three-dimensional viscous jets

Numerical investigations were made of the propagation, in a supersonic wake, of uncalculated jets, flowing out of nozzles of square and rectangular cross section, and of lumped jets, made up of from two to nine individual jets; the special characteristics of their flow were investigated in the initial, transitional, and main sections. Specifically, for lumped jets, the possibility of replacing them by a single axisymmetric jet, equivalent in mass-flow rate, is discussed. To calculate a three-dimensional unexpanded supersonic jet, flowing out into a wake, in [1] it was proposed to use a numerical method for solving a simplified system of Navier-Stokes equations for steady-state flow, and numerical investigations were made of the three-dimensional interaction of four jets in a supersonic wake, at small distances from the outlet cross section of the nozzle, i.e., mainly in the initial sections of the jets, where the mixing layers along the boundaries of the jets are still not closed. Here the method of [1] is used to study the special characteristics of three-dimensional viscous jets at large distances from the outlet cross section of the nozzle in the region of the main section, where the mixing layers have come together and a single three-dimensional jet has been formed. The system of equations, the boundary conditions, the numerical method, the system of coordinates, and the nomenclature used are the same as in [1].     

Flows of Supersonic Underexpanded Jets on the Range of Moderate Reynolds Numbers

The results of an experimental investigation of the gasdynamic structure of supersonic underexpanded air jets flowing out of a sonic nozzle into a low-pressure medium are presented. This setting of the experimentmakes it possible to achieve high values of the nozzle-to-ambient pressure ratio at moderate outflow Reynolds numbers characteristic of underexpanded jets issuing from micronozzles. The data on the supersonic core length, the laminar-turbulent transition location, and the jet flow characteristics are obtained. The results are compared with those obtained in microjets flowing out of sonic nozzles. Emphasis is placed on the earlier discovered effect of inverse transition of a turbulent jet into the laminar flow regime with increase in the Reynolds number.     

Effect of Spherical Recesses on the Characteristics of Coanda Flow

Sub- and supersonic flows past curvilinear surfaces with spherical recesses are investigated. The Coanda flow was created by a jet flowing out from a plane convergent nozzle into a submerged space along the tangent to a circular cylinder. The forces exerted on the cylinder and the total and static pressure profiles in Coanda jet cross-sections were measured. It is shown that the spherical recesses increase the friction drag at both sub- and supersonic velocities.     

Calculation of the Pulsed Jet of a Powder Water Cannon under Water

The results of a numerical investigation of a pulsed submerged water jet flowing out from the nozzle of a powder water cannon are given. A mathematical model of the process is constructed and the results of the numerical calculations for a water cannon of specific design are given. The water flow in the water cannon is considered in the quasi-one-dimensional formulation and the submerged jet propagation and its interaction with an obstacle are considered in the axisymmetric formulation. It is shown that the external conditions only slightly affect the water cannon parameters and that for various distances from the obstacle the maximum pressure of the pulsed jet on the obstacle is close to the initial jet dynamic pressure.     

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.     

Similarity with the outflow of strongly unexpanded jets into a hypersonic wake

The article discusses the outflow of a nonviscous gas from a strongly unexpanded supersonic nozzle into a supersonic wake. Under the assumption that the radius of the outlet cross section of the nozzle is negligibly small in comparison with the characteristic dimensions of the jet, expressions are obtained for the transverse and longitudinal dimensions of the jet, as well as similarity criteria determining the dimensionless gasdynamic functions. The satisfaction of the similarity criteria was verified by comparison with numerical calculations. Similarity with the outflow of strongly unexpanded jets was discussed in [1–3], where, specifically, the characteristic dimension of the flow was determined. In [4] it was demonstrated that the experimentally observed structure of the jet can be best described with the introduction of two characteristic dimensions, longitudinal and transverse. The effective construction of these two characteristic dimensions for the case of nonviscous outflow into a flooded space was carried out in [5], in which it was shown that using the longitudinal and transverse dimensions the geometries of the flow and the gasdynamic parameters are found to depend on the adiabatic index of the outflowing gas and on a parameter formed from the integral characteristics of the nozzle. The present work is a generalization of the results of [5] for the outflow of a jet into a hypersonic wake.     

Underexpanded wall jet in a cocurrent flow

The flow of a two-dimensional underexpanded wall jet flowing out of a sonic nozzle along a channel wall has been experimentally investigated. The dependence of the dimension of the first barrel of the jet on the underexpansion is obtained. It is shown that the flow of the jet in the channel is associated with a significant axial pressure gradient on the initial interval of the induced cocurrent flow and that this leads to a substantial change in the geometric dimensions of the jet.Translated from Izvestiya Rossiiskoi Akademii Nauk, Mekhanika Zhidkosti i Gaza, No. 1, pp. 196–199, January–February, 1993.     

Flow in a viscous jet escaping through a supersonic nozzle into a semi-infinite ambient space

The problem of an axisymmetric gas flow in a supersonic nozzle and in the jet escaping from the nozzle to a quiescent gas is solved within the framework of Navier-Stokes equations. The calculated pressure distribution is compared with that measured in the jet by a Pitot tube. The influence of the jet pressure ratio, Reynolds number, and half-angle of the supersonic part of the nozzle on nozzle flow and jet flow parameters is studied. It is shown that the distributions of gas-dynamic parameters at the nozzle exit are nonuniform, which affects the jet flow. The flow pattern for an overexpanded jet shows that jet formation begins inside the nozzle because of boundary-layer displacement from the nozzle walls. This result cannot be obtained with the inviscid formulation of the problem.     

Interaction of a heavy fluid flow in a channel with a transverse jet barrier

An experimental and numerical analysis of the interaction between a plane horizontal water flow in a rectangular channel (free water current) and a plane thin water jet (water jet curtain) is presented; the jet flows out vertically from either a slot nozzle in the bottom of the channel or the crest of a rigid spillway at a velocity appreciably (several times) greater than the water velocity in the channel. Numerical calculations were carried out using the STAR-CD software package preliminarily tested against the experimental data obtained. The dependence of the water level in the channel at a certain distance ahead of the jet barrier on the main jet parameters and the water flow rate in the horizontal channel is studied. It is found that in the region of the interface between the flows both steady and unsteady (self-oscillatory) flow patterns can be realized. Steady stream/jet interaction patterns of the “ejection” and “ejection-spillway” types are distinguished and a criterion separating these regimes is obtained. The notion of a rigid spillway equivalent to a jet curtain is introduced and an approximate dependence of its height on the relevant parameters of the problem is derived. The possibility of effectively controlling the water level ahead of a rigid spillway with a sharp edge by means of a plane water jet flowing from its crest is investigated. The boundary of transition to self-oscillation interaction patterns in the region of the flow interface is determined. The structure of these flows and a possible mechanism of their generation are described. Within the framework of the inviscid incompressible fluid model in the approximate formulation for a “thin” jet, an analytical dependence of the greatest possible depth of a reservoir filled with a heavy fluid at rest and screened by a vertical jet barrier on the jet parameters is obtained.     

Turbulence suppression in subsonic jets by high-frequency acoustic excitation

The influence of high-frequency acoustic excitation of a submerged round turbulent jet flowing out of a nozzle with both laminar and turbulent boundary layers at the nozzle outlet on the suppression of turbulent velocity fluctuations in the initial and transition regions of the jet is experimentally investigated. It is established that in the case of the turbulent boundary layer a higher excitation level is needed to realize the suppression effect than in the case of the laminar boundary layer. Moscow. Translated from Izvestiya Rossiiskoi Akademii Nauk, Mekhanika Zhidkosti i Gaza, No. 1, pp. 28–34, January–February, 1999. The study was carried out with the support of the Russian Foundation for Basic Research (project No. 96-02-19577).     

Flow in the peripheral zone of a freely expanding axisymmetric ideal-gas jet

When an ideal gas flows from a nozzle into a vacuum a substantial part of the jet is occupied by the peripheral zone in which the angle of inclination of the velocity vector W to the axis of symmetry is close to or exceeds /2. The known solutions [1–4] for the far field are unsuitable for describing the jet, since they are valid only at relatively small values of . In this study the author obtains an analytic solution describing in explicit form the shape of the streamlines and the distribution of the parameters in the peripheral zone of a jet flowing into a vacuum from a nozzle with an arbitrary parameter distribution in the exit section. At the nozzle edge the solution describes Prandtl-Mayer flow. As the radial coordinate tends to infinity, the streamlines tend to asymptotes whose angle of inclination depends on the distribution of the parameters in the nozzle exit section, and the local Mach numbers increase without bound.Translated from Izvestiya Akademii Nauk SSSR, Mekhanika Zhidkosti i Gaza, No. 3, pp. 145–153, May–June, 1987.     

On the possibility of blowing a gas jet into a supersonic flow without formation of a three-dimensional boundary-layer separation zone

We consider the flow formed by the interaction of a supersonic flow and a transverse sonic or supersonic jet blown at right angles to the direction of the main flow through a nozzle whose exit section is in a flat wall. When a gas jet is blown through a circular opening [1] the pressure rises in front of the jet because of the stagnation of the oncoming flow. This leads to separation of the boundary layer formed on the wall in front of the blowing nozzle. The resulting three-dimensional separation zone leads to a sharp increase in the pressure and the heat fluxes to the wall in front of the blowing nozzle, which is undesirable in many modern applications. The aim of the present investigation was to find a shape of the exit section of the blowing nozzle for which there is no three-dimensional separation zone of the boundary layer in front of the blowing nozzle.Translated from Izvestiya Akademii Nauk SSSR, Mekhanika Zhidkosti i Gaza, No. 3, pp. 162–165, May–June, 1979.     

Investigation of interaction between a plane transverse gas jet and a supersonic stream

The problem of interaction between a two-dimensional transverse gas jet emerging from a slot on a flat plate and a supersonic stream is considered. Several theoretical methods based on various approaches and physical models have been proposed to determine the characteristics of such a flow. The following fundamental directions can be isolated: a quasi-one-dimensional method [1], use of blast theory [2], and methods based on the equivalence of the effect of the jet and some solid on the external flow [3, 4]. However, the listed computational schemes [1–4] do not permit any clarification of the flow configuration in the jet and in the outer stream (the shock configuration, the jet boundaries, the distribution of the gasdynamic parameters in the flow field, etc.). Extensive experimental investigations of this phenomenon have been carried out simultaneously with the development of the theoretical methods, wherein the flow picture was determined, the pressure distribution was measured in the interaction domain, etc. [5, 6]. A computation method is proposed in this paper which will permit a detailed investigation of the flow structure in the jet and in the outer flow outside the separation region. Underlying the method is a hypothesis verified experimentally: The separating streamline in the mixing layer of the separated boundary layer (the “constant mass∝ line) intersects the jet boundary at the point of maximum jet standoff from the nozzle exit towards the incoming stream.     

Fluorescence depolarisation monitoring of liquid flow before and after exiting a slit nozzle

Steady-state fluorescence depolarisation was used to study the hydrodynamics of ethylene glycol flow inside a quartz slit nozzle for 24 mm ( Re~200) and outside as a free thin jet, for 14 mm. The polarisation profiles (over 1000 points) allowed direct evaluation of the velocity gradient within the flowing liquid from this molecular-level probe. Inside the nozzle two lateral boundary layers were observed. The velocity profile was flattened, which was attributed to strong chemical interactions with the walls of the cell. Within the jet, four polarisation profile maxima were observed for the first time, corresponding to two internal converging streams.     

燃气射流冲击传热特性的数值模拟

针对射流传热问题,利用基于RNGk-ε湍流模型的数值方法模拟了射流垂直冲击平板的流动过程,并与实验数据比较,验证了模型的可行性。在此基础上,以火箭喷管入口参数为入口条件,建立了超音速燃气射流垂直冲击平板和冲击浸没平板的计算模型,分析了不同冲击条件下努塞尔数分布规律和温度分布规律, 论述了超音速射流传热的特性及影响传热特性的因素。得到了冲击距离为(14~18)D的努塞尔数取值范围,并表明冲击距离和射流温度是影响传热效率的关键因素;冲击距离增加,传热效率降低,冲击平板表面的射流温度越高,传热效率越高。     

Effect of the Nozzle Edge Shape on the Acoustic Sensitivity of a Jet

The effect of the nozzle edge shape on the acoustic sensitivity of jets, that is, on the dependence of the jet parameters on the amplitude and frequency of the acoustic oscillations produced by an external source, is experimentally studied. The investigation was performed for nozzle edge configurations, the variation of which did not result in a change in the jet characteristics without external acoustic excitation. This means that the change in the edge shape alone had no influence on the flow pattern at the nozzle exit or the boundary layer flow regime on the nozzle walls. Measurements of the dependence of the mean velocity and the velocity fluctuation intensity on the jet axis on the distance from the nozzle exit showed that a change in the nozzle edge shape can lead to a change in the acoustic sensitivity of the jet when the jet is exposed to external acoustic action.     

The study of a supersonic jet of rarefied argon plasma

We have carried out an experimental study of a supersonic jet of argon plasma flowing in a rarefied medium. We have measured the distribution of total thrust along the axis of the jet at various temperatures in the arc chamber of the plasmatron. Using spectroscopic methods, we obtained the axial and radial distributions of the electron concentration and temperature and of the concentration of excited atoms. With the help of a probe we measured the electron temperature and concentration at large distances from the nozzle tip.     

Some problems of turbulent electrohydrodynamic jets

The problem of an axisymmetric turbulent electrohydrodynamic jet exhausting from a nozzle into an interelectrode gap is formulated. A numerical method of integrating the system of equations describing this flow is developed. This method is used to investigate three-dimensional effects in the jet (expansion of the jet, reverse flows). The influence on the jet characteristics (currents of the charge carried out of the nozzle, jet diameter, etc.) of the geometrical and electrical parameters and also of purely hydrodynamic factors (level of turbulence, relative velocity of parallel flow, etc.) is investigated.Translated from Izvestiya Akademii Nauk SSSR, Mekhanika Zhidkosti i Gaza, No. 5, pp. 144–149, September–October, 1980.     

Investigation of the propagation of a two-dimensional wall jet over a step

The propagation of an underexpanded sonic jet over a flat end face has been experimentally investigated. As distinct from previous studies, the object of investigation is not a free jet, but a jet flowing from a nozzle along a horizontal surface. The total separation of the jet from the surface and its attachment to the end wall are related to the propagation characteristics of underexpanded wall jets. The effect of the total pressure in the jet and the height of the step on the separation of the jet and its attachment to the wall and, moreover, on the principal characteristics of the flow — the pressure in the base region, the extent of the circulation zone, the jet trajectory — is examined. The associated hysteresis effects are studied.Translated from Izvestiya Akademii Nauk SSSR, Mekhanika Zhidkosti i Gaza, No. 4, pp. 61–66, July–August, 1991.