Unsteady expansion of a jet of dusty gas with high particle concentration into a vacuum

Translated from Izvestiya Rossiiskoi Akademii Nauk, Mekhanika Zhidkosti i Gaza, No.2, pp. 181–184, March–April, 1992.     

The penetration of a jet into a channel

The method of S. A. Chaplygin [1], as generalized by S. V. Fal'kovich [2] to the case of a few characteristic velocities, is used to solve the two-dimensional problem of the penetration of a subsonic jet of compressible fluid flowing at an angle from a slit into a stream of the same fluid bounded by parallel walls. The problem is solved for the case of an incompressible fluid by passing to the asymptotic limit. Using the tables of [3] the compression coefficient is calculated for a stream of gas merged with an incompressible fluid.     

Optimal penetration of a liquid jet into an obstacle

The velocity distribution and cross-sectional area along a jet which will assure maximum depth of penetration are found for a given jet energy within the framework of the hydrodynamic theory of liquid jet penetration into an obstacle. Also found is the velocity distribution along the jet which will assure ultimate tension of its elements upon approaching the obstacle. The possibility is exhibited of applying the theory elucidated to construct cumulative charges with elevated punch-through capacity.     

Unsteady jet flow of a viscous fluid

A solution is obtained, within the framework of the boundary layer theory, to the problem of the unsteady flow created by a two-dimensional jet source for a given momentum flux variation with time. In particular, aperiodic and periodic momentum variations are examined, and a qualitative analog with turbulent flow is noted for the latter.     

Formation of a jet of gas outflowing into evacuated space

Unsteady outflow from a sonic nozzle with off-design factor 4 · 10⁸ at an ambient pressure of 2 · 10^?5 mm Hg is studied by means of the absorption of an electron beam. The motion laws of the front of the outflowing gas and other characteristic regions of the outflow are studied. A comparison to the results of other works clarifies the features of outflow with high offdesign factors. An equation is obtained describing the motion of the front of outflowing gas along the flow axis. Results are presented in generalized similitude parameters.     

Unsteady filtration of a gas

The unsteady filtering flow of a gas described by the equations of motion proposed by Khristianovich in [1] is investigated. It is shown that for the gas flow in the pores a critical regime can develop when the reduced velocity (an analog of the Mach number in gas dynamics) is less than unity. The reduced velocity is the ratio of the flow velocity to the velocity of propagation of small filtering perturbations at a given point of the flow. St Petersburg. Translated from Izvestiya Rossiiskoi Akademii Nauk, Mekhanika Zhidkosti i Gaza, No. 1, pp. 201–203, January–February, 1994.     

Kinetics of degradation of a molecular beam in a gas at rest

Conclusion Based on a direct simulation, comprehensive and systematic studies of the degradation kinetics of a molecular beam at rest made it possible to reveal the qualitative and quantitative relaxation characteristics of the molecular beam to thermal equilibrium with the background gas within the ranges of mass ratios of the injected and background gases 0.1–20 and within velocity ratios of the injection for model molecules as hard spheres. The conclusions on the qualitative character of degradation are valid for a wider spectrum of parameters as well. As is established, at an energy of the injected molecules exceeding that of the background gas, during relaxation, a shock effect, i.e., the exceeding of the thermal energy of the injected gas over that of the background gas, is observed. Having been evaluated by analogy with supersonic-flow deceleration, the shock effect is the stronger, the closer the molecules of the injected and background gases in their masses. An initial increase in the energy of the injected molecules that is more considerable for light molecules has been discovered. The dependence of the energy relaxation length on the ratio of the masses and initial velocities of injected molecules has been established. The data obtained allow us to estimate the dimensions of the region of nonequilibrium mixing of injected and background gases with small values of the intensity of molecular flow in the beam. Kutateladze Institute of Thermal Physics, Siberian Division, Russian Academy of Sciences, Novosibirsk 630090. Translated from Prikladnaya Mekhanika i Tekhnicheskaya Fizika, Vol. 38, No. 4, pp. 103–110, July–August, 1997.     

Heat transfer from a heated sphere in a rarefied gas at rest

We consider the problem of heat transfer from a slightly heated sphere in a resting rarefied gas. We assume that the Krook equation is valid in this case. Two forms of the basic equations are presented, and relations are given which are obtained as a result of calculations of the heat flux and the temperature jump at the sphere surface as a function of a parameter which is inversely proportional to the Knudsen number. The results obtained are compared with results given by the known approximate theories.In conclusion the author wishes to thank M. N. Kogan for proposing the problem and for numerous discussions.     

Unsteady flow regimes of a nonrectilinear polymer jet under tension

The flow of a free jet of polymer solution or melt between a nozzle supplying fluid at a constant flow rate and a takeoff device in the form of a uniformly rotating roll is studied. The exit and takeoff points (the latter being the point at which the jet touches the roll surface) are on the same level, while the jet itself lies in a vertical plane. The jet sags under gravity by an amount that depends on the tension, the fluid density, the flow zone length, and the relationship between the takeoff and exit velocities.Translated from Izvestiya Rossiiskoi Akademii Nauk, Mekhanika Zhidkosti i Gaza, No. 3, pp. 47–54, May–June, 1995.The author wishes to thank V. M. Entov for his interest in the work.     

Numerical analysis of critical jet penetration

In this paper, a computational program for two dimensional unsteady compressible, elastic-plastic flow is used to study low speed jet penetration into a steel target. Based on the computational results, the dynamic process of penetration can be distinguished into two stages, cratering and steady penetrating. This is in agreement with the jet penetration mechanism developed by Cheng Che Min in 1972^[1,2]. The consumption of the jet energy is discussed and the value of the critical jet velocity, which represents the strength resistance of the target, is estimated.     

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.     

Influence of the wall boundary layer thickness on a gas jet injected into a liquid crossflow

The effects of the wall boundary layer thickness on the development of an axisymmetric gas jet injected into a confined vertical water flow were investigated. The variations in the wall boundary layer were made by using suction at the wall through rectangular profiled slots. The water velocity around the two-phase jet was studied for several boundary layer thickness values by laser Doppler velocimetry. The gas jet outline was extracted by image processing applied on visualisations for a wide variety of water, gas and suction conditions. These comparisons showed that the boundary layer has no influence on jet development. The data showed that the interactions between flows near the injection do not develop downstream, which accounts for the absence of the two classical contrarotating vortices in the medium field of the jet. The influence of the gas pocket, and then of buoyancy, is predominant over other phenomena. Received: 15 December 1999 / Accepted: 29 August 2000     

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.     

Planar jet flow of a radiating gas

Propagation of a laminar jet of a thermodynamically equilibrious gray gas is examined in the boundary layer theory approximation. The one-dimensional radiative energy transport is accounted for in the P ₁ approximation of the spherical harmonic method. Numerical solution of the problem is made under additional simplifying assumptions for various values of the radiation parameters to illustrate the radiation effect. The method and the computational scheme used are applicable to the study of complex jet flows of a radiating gas.The author thanks Yu. P. Lun'kin for his assistance in posing the problem and for his continued interest in the study.     

大锥角聚能装药射流形成及对多层靶侵彻的数值模拟研究

运用改进的网格线示踪点法MOCL(MarkOnCellLine)二维多流体欧拉程序 ,对大锥角聚能装药射流的形成及侵彻多层金属靶的全过程进行了数值模拟研究 ,计算结果与试验结果较吻合。这种连贯性的模拟能力避免了数值计算中对射流的许多人为假定。计算和试验结果表明 ,该聚能装药所形成的射流质量约占整个药型罩质量的 32 % ,兼有聚能射流和爆炸成型弹丸的特点 ,更适合于穿透多层大间隔金属靶。