Volume 89, №2
NONLINEAR EFFECTS OF FILTRATION IN TRANSIENT OPERATING REGIMES OF WELLS
A model problem on the recovery and redistribution of pressure fields in the stratum on reduction in the fl ow rate of wells has been solved on the basis of the law of filtration with a limiting gradient proposed earlier. The possibility of judging the fi ltration properties of the stratum from the form of the pressure recovery curve has been shown. It has been established that an analysis of this curve enables one to reveal a deviation of the fi ltration law from Darcy′s linear law in low-permeability strata.
Author: V. Sh. Shagapov and O. V. Dudareva
Keywords: nonlinear filtration, ultralow permeability, limiting pressure gradient, pressure recovery, finite difference method
MOTION OF PARTICLES IN A GAS STREAM IN THE PRESENCE OF TANGENTIAL AND AXIAL BLOWING
Radial distributions of the velocity components of particles in a vertical vortex chamber in the presence of axial (bottom) blowing under conditions of quasi-solid rotation are considered, and the dependence of the particle rotation
frequency on the Stokes number and the fraction of bottom blowing has been established
Author: Yu. S. Teplitskii, E. A. Pitsukha and O. V. Prokopovich
Keywords: cyclone-layer furnace, vortex chamber, centrifugal force, resistance force, gas velocity, particle velocity, Stokes number, bottom blowing
MATHEMATICAL MODELING OF MASS TRANSFER IN LAMINAR MOTION OF A DROPLET IN A LIQUID MEDIUM
Consideration is given to mathematical modeling of the process of nonstationary liquid–liquid extraction in apparatuses with free motion of a dispersed phase. Solutions of nonstationary equations of transfer of momentum and mass in the boundary layer on the droplet and inside the droplet near the phase boundary are given. Equations for calculation of the coeffi cients of mass transfer and concentration of the extracted component are obtained. A comparison is made of the calculated data and experimental results in extracting various liquid mixtures.
Author: D. V. Elizarov, V. V. Elizarov, T. S. Kamaliev and S. G. D′yakonov
Keywords: droplet of a liquid, laminar boundary layer, liquid–liquid extraction
REGIMES OF SPREADING OF A WATER DROPLET OVER SUBSTRATES WITH VARYING WETTABILITY
The authors have presented the results of experimental investigations into the physical mechanisms of change in the dynamic angle of contact of a droplet of distilled water on a substrate under the conditions of its wetting at high velocities of motion of the three-phase contact line. The investigations were carried out on three copper substrates and one superhydrophobic substrate. The authors have singled out three regimes of spreading of the droplet on the copper substrates with different surface roughnesses: formation of a droplet, spreading of the droplet, and formation of an equilibrium angle of contact. A distinctive feature of the droplet spreading over the surface with a superhydrophobic coating has been revealed, which lies in the monotonic increase in the advancing dynamic contact angle. The infl uence of the volume rate of formation of a droplet on the value of the dynamic contact angle has been established. On the copper surfaces with roughnesses of 5.190 and 6.210 μm, increase in the rate tended to increase the maximum value of the contact infl ow wetting angle. However, on the copper surface with a roughness of 0.591 μm, the dynamic contact angle was independent of the droplet′s volume in the range of volume rates of droplet growth 0.040–0.160 ml/s.
Author: G. V. Kuznetsov, D. V. Feoktistov, and E. G. Orlova
Keywords: regimes of spreading, superhydrophobic coating, dynamic contact angle, three-phase contact line, volume rate of formation of a droplet
ACOUSTOCONVECTION DRYING OF MEAT
The dynamics of moisture extraction from meat samples by the acoustoconvection and thermoconvection methods has been investigated. To describe the dynamics of moisture extraction from meat, we propose a simple relaxation model with a relaxation time of 8–10 min in satisfactorily describing experimental data on acoustoconvection drying of meat. For thermoconvection drying the relaxation time is thereby 30 and 45 min for the longitudinal and transverse positions of fi bers, respectively
Author: A. A. Zhilin and A. V. Fedorov
Keywords: acoustoconvection and thermoconvection drying, meat, muscle fibers
INFLUENCE OF THE ELECTRIC FIELD ON THE ULTRASONIC CAPILLARY EFFECT
Results of investigation into the influence of the electric fi eld on the ultrasonic capillary effect are presented. An analysis of the dependence of the height of rise of the liquid in the capillary on the electric-fi eld voltage is made. Experimental dependences of the height of rise of the liquid on the diameter of the capillary and on the depth of position of the capillary tip relative to the liquid surface are obtained.
Author: Ch. B. Daulbaev, D. U. Bodykov, E. T. Aliev and Z. A. Mansurov
Keywords: capillary effect, excitation and propagation of ultrasonic waves in the liquid, Rayleigh–Plesset equation
EXPERIMENTAL INVESTIGATION OF THE EFFECT OF PRODUCTION FACTORS ON THE PROPERTIES OF PEAT BRIQUETTES
The influence of the compacting pressure and moisture content of a raw peat material on such properties of fuel briquettes as the density, volume heat of combustion, compressive mechanical strength, hardness, and water absorption has been determined. Based on the results of investigations, regression dependences, characterizing the functional relationship between the noted compaction conditions and the quality indices of peat fuel, have been obtained. The optimal values of the compacting pressure and moisture content of peat that correspond to the most energy-effi cient compaction regimes have been substantiated.
Author: Sh. A. Piralishvili, A. A. Birfel′d, E. G. Stepanov, A. S. Mikhailov, and N. S. Spesivtseva
Keywords: peat, briquettes, compaction, fuel, energy effi ciency, compacting pressure, moisture content of raw materia
MATHEMATICAL MODELS OF HEAT CONDUCTION WITH A TWO-PHASE LAG
A mathematical theory has been developed for boundary-value problems of nonstationary heat conduction with a dual-phase lag. Features of analytical solutions of such heat problems are described. On the basis of the integral transformations proposed, an exact analytical solution of the practically important third boundary-value problem on the indicated heat conduction in the general formulation (plate, cylinder, sphere) has been obtained in the form of new functional constructions.
Author: E. M. Kartashov
Keywords: heat conduction, two-phase lag, thermal relaxation, density of a heat flow, temperature gradient
GENERAL BOUNDARY-VALUE PROBLEMS FOR THE HEAT CONDUCTION EQUATION WITH PIECEWISE-CONTINUOUS COEFFICIENTS
A constructive scheme for the construction of a solution of a mixed problem for the heat conduction equation with piecewise-continuous coeffi cients coordinate-dependent in the fi nal interval is suggested and validated in the present work. The boundary conditions are assumed to be most general. The scheme is based on: the reduction method, the concept of quasi-derivatives, the currently accepted theory of the systems of linear differential equations, the Fourier method, and the modifi ed method of eigenfunctions. The method based on this scheme should be related to direct exact methods of solving mixed problems that do not employ the procedures of constructing Green′s functions or integral transformations. Here the theorem of eigenfunction expansion is adapted for the case of coefficients that have discontinuity points of the 1st kind. The results obtained can be used, for example, in investigating the process of heat transfer in a multilayer slab under conditions of ideal thermal contact between the layers. A particular case of piecewise-continuous coeffi cients is considered. A numerical example of calculation of a temperature field in a real four-layer building slab under boundary conditions of the 3rd kind (conditions of convective heat transfer) that model the phenomenon of fi re near one of the external surfaces is given.
Author: R. M. Tatsii and O. Yu. Pazen
Keywords: reduction, quasi-derivative, Cauchy matrix, Fourier method, method of eigenfunctions
MULTIPLE INTEGRATION OF THE HEAT-CONDUCTION EQUATION FOR A SPACE BOUNDED FROM THE INSIDE
An N-fold integration of the heat-conduction equation for a space bounded from the inside has been performed using a system of identical equalities with defi nition of the temperature function by a power polynomial with an exponential factor. It is shown that, in a number of cases, the approximate solutions obtained can be considered as exact because their errors comprise hundredths and thousandths of a percent. The method proposed for N-fold integration represents an alternative to classical integral transformations.
Author: V. A. Kot
Keywords: heat-conduction equation, multiple integration, cavity in a space, approximate integral method, approximation error, convergence
EXPERIMENTAL INVESTIGATION OF THREE-DIMENSIONAL TURBULENT JETS ISSUING FROM A NOZZLE WITH A RECTANGULAR OUTPUT SECTION
A detailed analysis of average dynamic characteristics of flow in a nozzle with a rectangular output section in relation to the nozzle aspect ratio parameter and Reynolds number has been carried out and its results have been generalized. It has been established that the fl ow velocity profi le on the jet axis in the nozzle is determined by the parameter of its aspect ratio and by the jet initial velocity. A semiempirical formula that describes well the change in the maximum flow velocity in the main section of a three-dimensional jet is suggested.
Author: S. I. Isataev, G. Toleuov, M. S. Isataev and Sh. A. Bolysbekova
Keywords: rectangular nozzle, aspect ratio parameter, axisymmetric jet, three-dimensional turbulent jet, coherent structure
MATHEMATICAL MODEL OF THE PROCESSES OF HEAT AND MASS TRANSFER AND DIFFUSION OF THE MAGNETIC FIELD IN AN INDUCTION FURNACE
We propose a mathematical model describing the motion of a metal melt in a variable inhomogeneous magnetic field of a short solenoid. In formulating the problem, we made estimates and showed the possibility of splitting the complete magnetohydrodynamical problem into two subproblems: a magnetic fi eld diffusion problem where the distributions of the external and induced magnetic fi elds and currents are determined, and a heat and mass transfer problem with known distributions of volume sources of heat and forces. The dimensionless form of the heat and mass transfer equation was obtained with the use of averaging and multiscale methods, which permitted writing and solving separately the equations for averaged fl ows and temperature fi elds and their oscillations. For the heat and mass transfer problem, the boundary conditions for a real technological facility are discussed. The dimensionless form of the magnetic fi eld diffusion equation is presented, and the experimental computational procedure and results of the numerical simulation of the magnetic fi eld structure in the melt for various magnetic Reynolds numbers are
described. The extreme dependence of heat release on the magnetic Reynolds number has been interpreted.
Author: A. V. Perminov and I. L. Nikulin
Keywords: induction melting, superalloy, variable magnetic fi eld, magnetic fi eld diffusion, inductive current, heat and mass transfer, convection, multiscale method, averaging method
INFLUENCE OF THE POSITION OF A PARTICLE AND OF THE DRAG COEFFICIENT ON THE DRIFT VELOCITY IN AN ACOUSTIC RESONATOR
A study has been made of the drift velocity of particles in an acoustic resonator at the fi rst resonant frequency in standing and periodic shock waves. The notion of a local equilibrium velocity of particle drift has been introduced. A family of problems on the particle drift has been investigated numerically at different Mach and Reynolds numbers. The drift velocities of a particle have been plotted versus the drag coeffi cient and the position. The drag coeffi cient at which the particle drift velocity peaks has been found. At small and large drag coeffi cients, the particle drift velocity tends to zero. It has been shown that the maximum velocity of particle drift in the standing wave is one to two orders of magnitude smaller than that in the periodic shock wave.
Author: D. A. Gubaidullin, P. P. Osipov, and R. R. Nasyrov
Keywords: particle drift, drag coefficient, acoustic resonator
EXPERIMENTAL INVESTIGATION OF THE INSTABILITY OF THE MECHANICAL EQUILIBRIUM OF A FOUR-COMPONENT MIXTURE WITH BALLAST GASES
The instability of the mechanical equilibrium of the diffusion mixing of a four-component mixture with ballast gases by the two-flask method was investigated experimentally. The main gases helium and methane were diluted with nitrous oxide and propane, respectively. An analysis of the evolution of the diffusion mixing of these gases with time has shown that, in the case where the diffusion proceeding in a system with a ballast gas is unstable, in it there arises circulation of the gas-diluent by the diffusion channel from one flask to the other of a diffusion apparatus. It was established that the circulation of the ballast gas by the diffusion channel makes it possible to sustain the unsteady multicomponent diffusion during a long time and, in so doing, to decelerate the change of this regime to the regime of stable mass transfer
Author: M. S. Moldabekova, M. K. Asembaeva, and A. A. Akzholov
Keywords: diffusion, ballast gas, convection, two-fl ask apparatus, instability, mechanical equilibrium
EFFICIENCY OF ENERGY SEPARATION IN A VORTEX FLOW
A model swirling flow in a Ranque vortex tube, representing a vortex flow at the periphery and a forced vortex in the central part, was analyzed. The theoretical inferences obtained on the basis of the model proposed are in satisfactory
agreement with experimental data.
Author: V. D. Tyutyuma
Keywords: Ranque–Hilsch effect, vortex, swirling fl ow, velocity field, thermodynamic parameters
PLANE WAVES IN A ROTATING MONOCLINIC MAGNETOTHERMOELASTIC MEDIUM
The governing equations for a rotating monoclinic magnetothermoelastic medium are formulated in the context of the Lord–Shulman theory and are solved to yield the velocity equation that points to the existence of three quasiplane waves. Some particular cases are obtained, i.e., waves in the absence of anisotropy, rotation, and thermal and magnetic fi elds. A procedure for computing the angles of reflection is carried out. A numerical example is considered to show the dependence of the speeds of various plane waves on the angle of incidence, angle of reflection, rotation rate, and magnetic field strength.
Author: B. Singh and A. K. Yadav
Keywords: Lord–Shulman thermoelasticity, anisotropy, rotation, magnetic fi eld, plane waves
SECOND-LAW ANALYSIS OF THE PERISTALTIC FLOW OF AN INCOMPRESSIBLE VISCOUS FLUID IN A CURVED CHANNEL
The present investigation extends a consideration of peristaltic fl ow in curved channels through the second-law analysis. The lubrication approximation is employed to linearize the momentum, energy, and entropy generation rate equations. The stream function and temperature distribution are used to calculate the entropy generation number and the Bejan number. It is shown that the entropy generation rate in a peristaltic pump increases with the occlusion parameter. The entropy generation increases at the upper wall and decreases near the lower wall of the peristaltic channel as the curvature parameter increases. A curved surface acts as a strong source of entropy generation.
Author: V. K. Narla, K. M. Prasad, and J. V. Ramana Murthy
Keywords: peristaltic fl ow, curved channels, second-law analysis, entropy
COMBUSTION OF A METHANE–AIR MIXTURE IN A SLOT BURNER WITH AN INERT INSERT IN MASS TRANSFER TO THE ENVIRONMENT
A problem on combustion of a methane–air mixture in a slot burner with an internal insert in mass transfer from the burner′s exterior wall to the environment has been solved. A mathematical formulation of the problem takes account of the dependence of the diffusion, thermal-conductivity, and heat-transfer coeffi cients on temperature, and also of the heat removal from the gas to the environment by convective and radiant heat transfer. A numerical investigation has been carried out in a one-dimensional mathematical formulation of the problem in dimensional variables. The boundary of existence of a stable high-temperature regime of combustion of the methane–air mixture has been determined as a function of the rate of feed of the gas, the environmental temperature, and the width of the flow area of the burner
Author: A. Yu. Krainov and K. M. Moiseeva
Keywords: slot burner, methane–air mixture, internal insert, thermal expansion, steady-state combustion, radiant heat transfer
MATHEMATICAL MODELING OF COMBUSTION OF A MIXTURE OF ULTRADISPERSE ALUMINUM POWDER WITH WATER
The authors present a physicomathematical model of combustion of a mixed solid fuel in the form of a mixture of ultradisperse aluminum powder with gel-like water. The model takes account of the combustion of aluminum particles in steam, the motion of combustion products, and the lag of the velocity of motion of the particles behind that of the gas. The results of calculating the combustion rate are consistent with experimental data on the dependence of the rate of combustion of the mixture of ultradisperse aluminum powder with water on pressure.
Author: A. Yu. Krainov, D. A. Krainov, and V. A. Poryazov
Keywords: ultradisperse aluminum powder, water, rate of combustion, processes in the gas phase, mathematical modeling
INVESTIGATION OF THE EFFECT OF THE COMBUSTION SITE ON WOOD SPECIMENS WITH THE USE OF IR DIAGNOSTICS
We have investigated under laboratory conditions the effect of the combustion site modeled by a steppe combustible on wood specimens of different profi les (fl at and cylindrical specimens) with the use of IR diagnostics. Experiments were carried out with the use of a JADE J5330SB infrared imager in the spectral range of 2.64–3.25 μm. The temperature profi les on the surface of wood specimens of different forms (fl at and cylindrical specimens) have been obtained and the heat-stressed parts under the action of the model combustion site imitating a low-intensity low forest fi re have been determined.
Author: V. P. Zima and D. P. Kasymov
Keywords: wood, IR diagnostics, experiment, ignition, ignition probability
DEPOSITION OF FUNCTIONAL COATINGS FROM AN ACETYLENE-CONTAINING PLASMA AT ATMOSPHERIC PRESSURE
Properties of thin coatings formed on polymer and glass substrates by plasma-enhanced chemical vapor deposition from a mixture of nitrogen with acetylene at atmospheric pressure were investigated. It was established that chemically stable transparent films with a mass ratio of fi xed carbon and nitrogen C:N ~ 2:1 are formed on the surface of these substrates. When the deposition time was increased, arrays of dendrite-like structures were formed on the substrates.
Author: F. V. Plevako, S. V. Gorbatov, P. A. Davidovich, E. M. Prikhod′ko, S. V. Shushkov, L. P. Krul′, G. V. Butovskaya, O. V. Shakhno, S. V. Gusakova, O. V. Korolik, and A. V. Mazanik
Keywords: high-frequency barrier gaseous discharge, polymerization in plasma, dicyanoacetylene, thin-film coating, dendrite-like structures
TRANSIENT PHENOMENA IN PROBE MEASUREMENTS IN LOW-DENSITY HELIUM AND OXYGEN PLASMA
Measurements of the probe characteristics in the pulsed mode in oxygen and helium plasma are presented. The question on the thickness of the near-probe space charge layer in the electron–ion, electron–ion–ion, and ion plasma is discussed. It has been shown that the presence of negative ions in the plasma leads to a drastic decrease in the thickness of the ion layer. A model of the formation of a near-probe layer in nonstationary low-pressure plasma is proposed. It been shown that a space charge layer is formed in the time of 5–6 collisions of ions with neutral particles. It has been illustrated that the displacement current has a linear dependence on the potential applied to the probe. The question concerning the value of the dielectric constant of the plasma is discussed.
Author: S. A. Gutsev
Keywords: low-pressure discharge, ion–ion plasma, Langmuir probes, volt–ampere characteristic, space charge layer
PLASMA TORCH DEVELOPMENT AND CRATER GROWTH DYNAMICS IN THE COURSE OF LASER PROCESSING OF MATERIALS AND ITS DIANGOSTICS
The evolution of the plasma torch arising under the action of laser radiation on a metal specimen has been investigated by several methods. The dependence of the time form and the spectrum of acoustic vibrations on the parameters of the irradiated material and the law of increase in the crater depth has been determined. It has been found that under the action of a lser pulse of length ~20 μs on the surface of a copper specimen the growth time of the destruction zone is about 40–50 μs, which is in good agreement with the lifetime of plasma formation near the surface of the target subjected to laser-plasma processing (~50 μs). It has been shown that the use of the model of a loaded zone with moving boundaries emitting acoustic waves into an elastic medium permits solving an important practical problem — determining the law of time growth of the zone of irreversible deformations on the surface of the specimen subjected to pulsed laser plasma processing
Author: S. V. Vasil′ev, A. Yu. Ivanov, A. V. Kopytskii, and V. I. Nedolugov
Keywords: laser radiation, high-speed holographic cinephotography, erosion plasma torch, crater, acoustic emission
SELF-ORGANIZATION OF A LAMINAR STRUCTURE OF A NORMAL GLOW DISCHARGE
The behavior of a glow discharge at low pressures is considered. A combined experimental and theoretical method for determining the distributions of electron and ion concentrations in the discharge chamber is proposed. It is shown that the concentrations of charged particles in the negative glow rise not due to the intense ionization by fast electrons from the cathode regions, but instead due to the slowing down of their drift motion. The use of an experimental curve of the potential distribution along a discharge chamber and account of the nonlocal dependence of the Townsend coeffi cient on the electric fi eld strength have allowed obtaining the distribution of the electric fi eld strength and determining the exact character of variation in the concentration of charged particles along the discharge axis.
Author: B. A. Timerkaev, O. A. Petrova, and A. I. Saifutdinov
Keywords: glow discharge, cathode, electrode regions, positive column, Faraday dark space
APPROXIMATE SOLUTION OF A CONJUGATE PROBLEM OF HEAT AND MASS TRANSFER THROUGH AN INTERFACE
Evaporation of liquid into the vapor space and evolution of a system to thermodynamic equilibrium for the given parameters of the interaction potential of atoms are investigated using argon as an example. As a result of calculation ,
the liquid–vapor equilibrium saturation line is obtained, which agrees with the corresponding experimental dependence.
Author: I. N. Shishkova and A. P. Kryukov
Keywords: heat and mass transfer through an interface, velocity distribution function of molecules, Boltzmann kinetic equation, intermolecular interaction potential
ON THE INFORMATION CONTENT OF THE RESULTS OF MEASUREMENTS
Based on the introduced measure of experimental information, an approach is suggested that simplifi es the planning of an experiment, as well as the processing and interpretation of its results. The approach considered is quite universal and can be used in experimental investigation of a wide range of processes (phenomena) described by linear (relative to the parameters investigated) models. The results of numerical calculation that illustrate the effectiveness of the proposed approach are presented. The calculation is carried out with the aid of the example of solving a model problem of processing the results of nonstationary temperature measurements.
Author: N. I. Batura
Keywords: inverse problem, informativeness of measurements, amount of information in a measurement, statistically stable measurement, informative measurement, regularization method
DISTINCTIVE FEATURES OF THE TEMPERATURE SENSITIVITY OF A TRANSISTOR STRUCTURE IN A BIPOLAR MODE OF MEASUREMENT
Results are presented of an experimental investigation of the temperature sensitivity of an individual base-tocollector junction of a bipolar transistor structure and of this same structure in the case of series connection of blocking emitter and collector junctions. It is shown that the temperature-sensitivity coeffi cient of the transistor structure operating in a bipolar mode of measurement is an order of magnitude larger than an analogous coeffi cient of the base-to-collector junction.
Author: A. V. Karimov, D. P. Dzhuraev, Sh. M. Kuliev, and A. A. Turaev
Keywords: bipolar transistor, temperature pickup, temperature sensitivity, bipolar mode
ANALYSIS OF UNCERTAINTIES WITH THE EXAMPLE OF DIRECT AND INVERSE HEAT METERING PROBLEMS
The unique features of arithmetics, algebra, logic, and of the analysis of uncertainty functions as mathematical objects have been investigated. The means of overcoming the defi ciencies of the interval analysis and indistinct logic occurring due to the failure to account for the variability of the density function form are shown. An example of the application of the arithmetics of uncertainties to the analysis of the result of a multifactor experiment is given.
Author: A. V. Chernukho
Keywords: uncertainty, uncertainty density function, density function transformation, integral analysis, indistinct logic, multifactor experiment
OPTIMAL THERMAL DESIGN OF A MULTISHIELD THERMAL PROTECTION SYSTEM OF REUSABLE SPACE VEHICLES
We have solved the problem of the optimal thermal design of a multishield thermal protection system of reusable space vehicles due to the choice of the optimal position and materials of radiation shields.
Author: I. A. Maiorova, P. V. Prosuntsov, and A. V. Zuev
Keywords: reusable space vehicles, multilayer heat insulation, multishield thermal protection system, radiation screen
CONTROL OF EXTRUSION
The principle and engineering of a system for automatic control of the tension of the thread and the productivity of the process of extrusion of polyacrylonitrile fibers have been presented. The control system is based on the use of
functional features of a modern frequency controlled electric drive
Author: V. M. Zhuromskii
Keywords: polyacrylonitrile (PAN) fi bers, automatic control, spinneret, frequency controlled electric drive