Self-similar movement of a viscous gas in a channel

The results presented in [1] refer primarily to dropping liquids for which the influence exerted by the thermal conditions on the flow is related to the temperature dependence of the viscosity. The self-similar flow of a viscous gas in a channel with a linearly increasing wall temperature is examined in this paper. The influence exerted by the Reynolds and Prandtl numbers on heat exchange and the hydrodynamics of the flow is analyzed.Translated from Zhurnal Prikladnoi Mekhaniki i Tekhnicheskoi Fiziki, No. 3, pp. 47–54, May–June, 1976.The author wishes to thank A. F. Seleznev for carrying out the calculations and V. N. Shtern for discussing the paper.     

Influence of the atmosphere on the magnitude of the hydrodynamic forces in the case of a disk in a flat encounter with the surface of a compressible liquid

If the velocities with which bodies enter liquids are small, and the bodies are not too blunt, the magnitudes of the hydrodynamic forces can be satisfactorily determined in the framework of the approximation of an incompressible liquid and depend on the density of the liquid, the velocity of entry, and the geometrical parameters (shape of the body, angles of entrance and attack). If the velocity is increased or the encounter with the surface becomes nearly flat, the compressibility of the liquid and the presence of an atmosphere begin to influence the hydrodynamic forces significantly. The influence of the compressibility on the magnitude of the impact loads has been investigated theoretically and experimentally [1–8]. The influence of the atmosphere in the case of an incompressible liquid has also been taken into account [9–11]. In the case of a flat encounter the two factors (compressibility of the liquid and presence of the atmosphere) simultaneously influence the development of the impact process. The present paper reports experimental results and computer calculations of the impact loads in the case of a flat encounter of a disk and the surface of a compressible liquid in atmospheres of helium, air, and freon.Translated from Izvestiya Akademii Nauk SSSR, Mekhanika Zhidkosti i Gaza, No. 3, pp. 15–20, May–June, 1984.     

Parameters of spatial flow past a hydrofoil near the free surface of a ponderable liquid

An approach is presented to the investigation of spatial flow past an submerged hydrofoil in the presence of a ponderable liquid. The approach uses the method of singularities, which represents the influence of the free surface of the water by the influence of an unbounded layer of sources. The linear solution is completely found for the problem of determining the wave production and downwash behind an submerged hydrofoil with given parameters of the eddy system. An estimate is made of the influence on the flow characteristics of nonlinear factors associated with the change produced by the wave production in the form of the free eddies leaving the hydrofoil. The distribution of the downwash in the flow behind the hydrofoil is found and recommendations given for the arrangement of a hydrofoil system with positive interaction of the elements. The results of the calculation are compared with experiment.Translated from Izvestiya Akademii Nauk SSSR, Mekhanika Zhidkosti i Gaza., No. 2, pp. 54–62, March–April, 1979.     

Horizontal impact of a sphere half immersed in a liquid of finite depth

We consider the problem of bottom influence during horizontal hydrodynamic impact of a spherical solid body of diameter 2a which is half submerged in a liquid layer of finite depth. The sphere is subjected to the action of a shock pulse, as a result of which it acquires an initial translational velocity u directed along the x-axis.The influence of the spherical bottom on the sphere impact phenomenon was first studied by Zhukovskii [1]. Vertical impact in a layer of finite thickness was considered in [2]; horizontal impact in a halfspace was examined in [3].     

Diffusion of a ring vortex

The diffusion of a ring vortex is investigated in the present paper with allowance for the influence of the initial radius of the toroidal vorticity distribution on the flow structure. The statement of the problem in such a formulation makes it possible to classify and reinterpret results obtained previously. A vortex pair is studied together with a vortex ring. The toroidal vorticity and stream function distributions are obtained analytically. The self-induced lift velocity of the ring vortex is found. The influence of inertial terms is investigated numerically.Translated from Izvestiya Akademii Nauk SSSR, Mekhanika Zhidkosti i Gaza, No. 6, pp. 10–15, November–December, 1987.     

Numerical Study of the Aerodynamic Performance of a Train with a Crosswind for Different Embankment Heights

A numerical study using improved delayed detached eddy simulation (IDDES) was used to investigate the influence of the embankment height on the aerodynamic performance of a high-speed train travelling under the influence of a crosswind. The results of the flow predictions were used to explore both the instantaneous and the time-averaged flows and the resulting aerodynamic forces, moments and slipstreams. An increase of the aerodynamic drag and side forces as well as the lift force of the head and middle cars were observed with rising embankment height. While the lift force of the tail car decreased with the increasing embankment height. Furthermore, the height of the embankment was found to have a strong influence on the slipstream on the leeward side of the train. The correlation between the embankment height and the slipstream velocity on the windward side, was rather small. The flow structures in the near-wake of the leeward side of the train, responsible for the aerodynamic properties of the train were analyzed, showing strong dependency on the embankment height.

     

Radiation of a shock layer during hypersonic flow of air about a spherical segment

The problem on the flow of radiating air about a spherical segment is solved. A comparison of results obtained with investigations of the flow of a radiating gas about a sphere and the flow of gas about a spherical segment, with radiation left out of account, is made. The influence of radiation in the neighborhood of the rim of the segment on the flow in the shock layer is considered, and it is shown that it does not exert a significant influence on the fields of the gas-dynamical parameters because the latter are determined by processes occurring near the axis of symmetry, due to the phenomenon of radiation freezing.Moscow. Translated from Izvestiya Akademii Nauk SSSR, Mekhanika Zhidkosti i Gaza, No. 1, pp. 101–106, January–February, 1972.     

Nonlinear dynamic behaviors of a rotor-labyrinth seal system

The nonlinear model of rotor-labyrinth seal system is established using Muszynska’s nonlinear seal forces. We deal with dynamic behaviors of the unbalanced rotor-seal system with sliding bearing based on the adopted model and Newmark integration method. The influence of the labyrinth seal one the nonlinear characteristics of the rotor system is analyzed by the bifurcation diagrams and Poincare’ maps. Various phenomena in the rotor-seal system, such as periodic motion, double-periodic motion, quasi-periodic motion and Hopf bifurcation are investigated and the stability is judged by Floquet theory and bifurcation theorem. The influence of parameters on the critical instability speed of the rotor-seal system is also included.     

Experimental study of the unsteady aerodynamic field outside a tunnel during a train entry

The compression wave generated by a train entering a tunnel has been widely studied. However; the resulting exit flow created at the tunnel portal has never been investigated. The experimental work reported in the present paper provides some insight into the structure of this flow and its main characteristics. Experiments were conducted with a 1/140th scale apparatus and the explored range of the train speed was 5–50 m/s (M ≤ 0.15). The study focused on the influence of the train speed and the train nose geometry on the flow. Unsteady velocity measurements were taken to attempt to clarify the influence of the train speed on the jet induced at the tunnel portal when the train enters. A mass balance was undertaken to compare the quantity of air ejected from the tunnel to that compressed inside (i.e. involved in the compression wave). The study revealed that, at low speed, the quantity of air compressed to that ejected is of the order 5:1, subject to boundary conditions. At high speed, the volume ejected is comparable to that compressed. Interestingly, the train nose geometry does not influence the mass balance. The jet momentum was also calculated and found to increase with the train speed and is insensitive to the train nose geometry. Careful discussions are provided in the paper on how these results can be extended to the full-scale case. Received: 14 May 1999/Accepted: 27 April 2000     

Heat and mass transfer during solidification of a binary solution from a horizontal plate

This study deals with the experimental analysis of double diffusive effects on the solidification process of a binary mixture. Solidification experiments from a horizontal plate heat exchanger are performed in a cavity filled with a hypoeutectic NH₄Cl–H₂O solution. Solute redistribution at the interface creates concentration gradients in the fluid phase and a dendritic front growth is expected. We analyze the influence of solute rejection on the equilibrium conditions at the solid–liquid interface, on the solidification front kinetics and on the solid structure. Local front temperature measurements and estimation of the solid fraction of the growing solid allow us to quantitatively analyze the coupled influence of solute rejection and solid fraction on the front growth. A simplified numerical analysis shows that the role played by these two phenomena is very weak in the range of parameters under study.     

Flow boiling heat transfer and pressure drop of R-134a in a mini tube: an experimental investigation

This paper presents the results of an experimental study carried out with R-134a during flow boiling in a horizontal tube of 2.6 mm ID. The experimental tests included (i) heat fluxes in the range from 10 to 100 kW/m², (ii) the refrigerant mass velocities set to the discrete values in the range of 240-930 kg/(m² s) and (iii) saturation temperature of 12 and 22 °C. The study analyzed the heat transfer, through the local heat transfer coefficient along of flow, and pressure drop, under the variation of these different parameters. It was possible to observe the significant influence of heat flux in the heat transfer coefficient and mass velocity in the pressure drop, besides the effects of saturation temperature. In the low quality region, it was possible to observe a significant influence of heat flux on the heat transfer coefficient. In the high vapor quality region, for high mass velocities, this influence tended to vanish, and the coefficient decreased. The influence of mass velocity in the heat transfer coefficient was detected in most tests for a threshold value of vapor quality, which was higher as the heat flux increased. For higher heat flux the heat transfer coefficient was nearly independent of mass velocity. The frictional pressure drop increased with the increase in vapor quality and mass velocity. Predictive models for heat transfer coefficient in mini channels were evaluated and the calculated coefficient agreed well with measured data within a range 35% for saturation temperature of 22 °C. These results extend the ranges of heat fluxes and mass velocities beyond values available in literature, and add a substantial contribution to the comprehension of boiling heat transfer phenomena inside mini channels.     

Solution of a contact problem for a prestressed layer and punch

Conclusions On the basis of the analysis of the analytical solution and of the numerical computations, we can draw the following conclusions.the initial stresses in the layer affect significantly the distribution law of the contact stresses and displacements in the layer and in the cylinder (Figs. 1–5). This influence is noted in the cylinder for the sections <1 (Figs. 1, 2) and in the domain of the contact of the punch and the layer (Figs. 3–5).The initial stresses affect in an essential manner the character of the distribution of u₃, and depend on the quantity .For h>15, for the determination of the stress-strain state in the punch and in the layer, with a sufficient accuracy for engineering applications, one can use the solution for the semispace. Thus in this paper one obtains the analytic and graphical dependences, reflecting the influence of the initial stresses on the stress-strain state of the elastic punchlayer system with initial stresses. This influence is essential (Fig. 1–5) for both compressible and incompressible bodies and has to be taken into account at the calculations of machine components and constructions.Hmelnickii Institute of Light Industrial Technology, Translated from Prikladnaya Mekhanika, Vol. 23, No. 3, pp. 14–22, March 1987.     

On the interference of a weak and a strong shock wave in a dissociating nitrogen flow

The influence of the nitrogen dissociation on the interactions due to the interference of two planar shock waves in a hypersonic high enthalpy flow is theoretically investigated for infinite reaction rates. The two limiting cases of infinitely slow and infinitely fast reactions are modelled as a perfect gas and an ideal dissociating gas in chemical equilibrium.To investigate the influence of finite reaction rates on the interactions of shock waves, experiments are performed in the high enthalpy shock tunnel Göttingen (HEG) with a wind tunnel model consisting of a wedge type shock generator and a transversally mounted cylinder. The pressure and heat transfer loads resulting from the shock wave interferences are measured and the flow field is visualized by means of interferograms. The experimental results are compared with the results of a numerical simulation for a dissociating nitrogen flow and with the experimental results for a perfect gas flow.     

Investigation of the influence of the unit Reynolds number on the transition of a boundary layer on a sharp cone

To establish the influence of the unit Reynolds number on the transition of a boundary layer on the side surface of a cone, the transition was investigated on a model of a sharp cone with half-angle = 7.5 ° and lengths from 150 to 400 mm. The experiments were made in a shock tube at Mach number M = 6.1 in the wide range of Reynolds numbers Re_eL = 1.3·10⁶-5.5·10⁷. The position of the transition region was determined from the results of measurement of the local heat flux by calorimetric thermocouple converters. Data were obtained on the influence on the transition of the unit Reynolds number at large values. It was also shown that under the investigated conditions the base region does not influence the transition of the boundary layer on the surface of the cone.Translated from Izvestiya Akademii Nauk SSSR, Mekhanika Zhidkosti i Gaza, No. 4, pp. 32–38, July–August, 1982.     

Motion and heat and mass transfer in a disperse admixture in turbulent nonisothermal jets of a gas and a low-temperature plasma

The motion and heat and mass transfer of particles of a disperse admixture in nonisothermal jets of a gas and a low-temperature plasma are simulated with allowance for the migration mechanism of particle motion actuated by the turbophoresis force and the influence of turbulent fluctuations of the jet flow velocity on heat and mass transfer of the particle. The temperature distribution inside the particle at each time step is found by solving the equation of unsteady heat conduction. The laws of scattering of the admixture and the laws of melting and evaporation of an individual particle are studied, depending on the injection velocity and on the method of particle insertion into the jet flow. The calculated results are compared with data obtained with ignored influence of turbulent fluctuations on the motion and heat and mass transfer of the disperse phase. __________ Translated from Prikladnaya Mekhanika i Tekhnicheskaya Fizika, Vol. 49, No. 3, pp. 95–108, May–June, 2008.     

Hydroelastic interaction of a wedge-shaped construction entering a liquid

The aim of the paper is to create a mathematical model of the hydroelastic interaction of a wedge-shaped construction with a liquid that it enters. The various relevant factors — velocity and acceleration of elastic vibrations, influence of catinary forces, initial bending, and mobility of brackets — are to be taken into account as fully as possible.Translated from Izvestiya Rossiiskoi Akademii Nauk, Mekhanika Zhidkosti i Gaza, No. 3, pp. 118–125, May–June, 1993.     

On the question of the stability of powder combustion in a half-closed space

The influence of gas temperature perturbations on the stability of powder combustion in a rocket chamber is investigated theoretically on the basis of the Zel'dovich-Novozhilov theory of powder combustion. The influence of the bow space adjacent to the burning channel is also examined.Translated from Zhurnal Prikladnoi Mekhaniki i Tekhnicheskoi Fiziki, No. 6, pp. 74–79, November–December, 1971.     

Flow of a viscous liquid in the gap between a moving and a fixed sphere at low reynolds numbers

In recent years, the investigation of various physiological processes, and also the problem of developing an artificial heart have stimulated studies in which blood flow in the heart, and also in the large arteries is treated as the flow of a viscous incompressible Newtonian liquid. Different assumptions have been made concerning the geometry of the heart. For example, in [1, 2] a sphere was used as model of a ventricle, the influence of the entrance and exit valves was not taken into account, and, since the Reynolds number is normally fairly high, the blood flow was treated as the flow of an ideal incompressible liquid. In the experimental study of [3], the ventricle was modeled by an ellipsoid and allowance was made for the influence of the entry mitral valve; a simplified cylindrical geometry was used in [4]. In the present paper, the model of the ventricle is a sphere. Allowance is made for the influence of an artificial entry ball valve. Configurations of this kind are encountered in an artificial heart with hydraulic drive. To use the problem as an analytic test in further computer calculations at high Reynolds numbers, and also to obtain analytic estimates for the trajectories of Lagrangian particles, the treatment is restricted to flows for which the influence of the nonlinear terms in the Navier-Stokes equations can be ignored.Translated from Izvestiya Akademii Nauk SSSR, Mekhanika Zhidkosti i Gaza, No. 6, pp. 180–183, November–December, 1980.     

Ignition of hydrogen in a turbulent boundary layer on a plate

The ignition of hydrogen blown into a turbulent supersonic boundary layer on a flat plate is investigated numerically. It is assumed that the mixture consists of six chemically active components H, O, OH, H₂O, O₂, H₂ and inert nitrogen N₂. The boundary layer is divided into outer and inner regions, for which different expressions for the coefficients of turbulent transport are used. The influence of pulsations on the rates of the chemical reactions, and also the back reaction of the chemical processes on the mechanism of turbulent transfer are not taken into account. The surface of the plate is assumed to be absolutely catalytic with respect to the recombination reactions of the H and O atoms. The influence of the blowing intensity, the Mach number in the outer flow, and the pressure on the ignition delay is analyzed. The possibility of effective porous cooling of the surface when there is combustion in the boundary layer is demonstrated.Translated from Izvestiya Akademii Nauk SSSR, Mekhanika Zhidkosti i Gaza, No. 6, pp. 33–40, November–December, 1979.I thank V. G. Gromov and V. A. Levin for their interest in the work.     

Effect of wire diameter and overheat ratio near a conducting wall

The influence on several hot wire measurements of the diameter d and overheat ratio a of a wire placed near a conducting wall in a turbulent boundary layer is investigated. These measurements include the mean velocity and second, third and fourth order moments of the longitudinal velocity fluctuation u. A decrease in either d or a reduces the departure of the measured mean velocity from the expected linear sublayer value. The measured influence of d and a precludes the use of a universal correction for the mean velocity. There is no influence of a on the rms, skewness and flatness factors of u. Only a small increase is found in the skewness and flatness factors of u when d is decreased.