Yu. N. Grigor'ev1,2, S. V. Meleshko3, A. Suriyawichitseranee3 1Institute of Computational Technologies, Siberian Branch, Russian Academy of Sciences, Novosibirsk, 630090, Russia 2Novosibirsk State University, Novosibirsk, 630090, Russia 3School of Mathematics, Nakhon Ratchasima, 30000, Thailand
Keywords: уравнение Больцмана, изотропная функция распределения, функция источника, инвариантные решения, Boltzmann equation, isotropic distribution function, source function, invariant solutions
Exact solutions of a nonlinear Boltzmann kinetic equation with a source are constructed in the case of an isotropic distribution function and Maxwell model of isotropic scattering. These solutions are constructed with the use of an equivalence group such that one of its transformations uniquely identifies the class of the source functions that are linear in terms of the distribution function; moreover, the transformed equation has a zero right side. As a result, one can explicitly find invariant solutions of the type of the Bobylev-Krook-Wu solutions, in particular, those that admit physical interpretation.
V. A. Il'in, L. A. Ponomarev
Keywords: электроконвекция, слабопроводящая жидкость, переход в хаотическое состояние, electroconvection, low-conductivity fluid, transition to chaotic state
This paper describes the study of electroconvection of low-conductivity fluid in a capacitor with boundary conditions of adhesion on a solid surface in the case of rapid charge relaxation. The linear stability of fluid equilibrium in a constant electric field is investigated. The model describing the averaged fluid flow in a high-frequency electric field. The nonlinear modes of electroconvection are described. A mode map is constructed. It is established that, depending on the frequency of the external field, the transition to chaotic state occurs through quasiperiodic or intermittent structures.
L. H. Ingel'1,2 1Taifun Scientific and Production Association, Obninsk, 249038, Russia 2Obukhov Institute of Atmospheric Physics, Russian Academy of Sciences, Moscow, 119017, Russia
Keywords: конвекция, термики, турбулентность, интегральные модели, сдвиговые течения, нелинейность, аналитические решения, convection, thermals, turbulence, integral models, shear flows, nonlinearity, analytical solutions
The nonlinear integral model of a turbulent thermal is extended to the case of the presence of a horizontal component of its motion with respect to the medium (for example, the rise of a thermal in shear flow). In contrast to traditional models, the possibility of heat release in the thermal is taken into account. For a piecewise constant vertical horizontal velocity profile medium and a constant vertical velocity shear, analytical solutions are obtained which describe different dynamic modes of thermals. The nonlinear interaction between the horizontal and vertical components of thermal motion because each of them influences the rate of entrainment of the ambient medium, i.e., the rate of increase in the size of the thermal and, hence, its mobility. It is shown that the enhancement of the entrainment of the medium due to the interaction of the thermal with the cross flow can lead to a significant decrease in the mobility of the thermal.
D. A. Gadzhiev, A. M. Gaifullin
Central Aerohydrodynamic Institute named after N. E. Zhukovskii, Zhukovskii, 140180, Russia
Keywords: вихрь, отрыв пограничного слоя, диффузия вихря, "подскок" вихря, vortex, boundary layer separation, vortex diffusion, vortex «op up»
A numerical solution is found for the problem of evolution of two oppositely rotating vortices in a viscous incompressible fluid near a solid surface. The mechanism of vortex dissipation is determined. The trajectory of vortex motion is constructed.
O. A. Vlasova1, V. G. Kozlov1, N. V. Kozlov2 1Perm State Humanitarian Pedagogical University, Perm, 614990, Russia 2Institute of Continuous Media Mechanics, Ural Branch of Russian Academy of Science, Perm, 614013, Russia
Keywords: вращение, модуляция скорости, тяжелое тело, вязкая жидкость, подъемная сила, rotation, velocity modulation, heavy body, viscous fluid, lift force
The dynamics of a heavy cylindrical body in a liquid-filled horizontal cylindrical cavity with a time-varying rotation rate is experimentally investigated. The body is near the cavity boundary under a centrifugal force and undergoes solid-body rotation together with the liquid and the cavity at a fixed rotation rate. The dependence of the body dynamics on the amplitude and frequency of the rotation rate modulation is investigated. It is found that at a critical amplitude of modulation (at definite frequency), the heavy body repulses from the cavity boundary and comes into a steady state at some distance from the wall. It is found that the average lift force (repulsive one) is generated by the azimuthal oscillation of the body in the rotating frame of reference and manifests itself at a distance comparable to the thickness of the viscous boundary layer. In the experiments, we observed an azimuthal drift of the body due to asymmetric azimuthal oscillations of the body. In the limit of high frequency of the rotation rate modulation, the dependence of the lift force coefficient on the gap between the body and the wall is determined.
A. P. Konstantinov
Lavrentyev Institute of Hydrodynamics, Siberian Branch, Russian Academy of Sciences, Novosibirsk, 630090, Russia
Keywords: собственные колебания в неограниченных областях, акустический резонанс, тонкостенные препятствия в каналах и трубах, natural oscillations in unbounded regions, acoustic resonance, thin-walled obstacles in channels and tubes
Natural aeroacoustic oscillations of the gas near two thin plates arranged in a tandem manner in a rectangular channel are studied in a two-dimensional formulation. A bifurcation of natural frequencies depending on the distance between the plates is detected, and the frequency of natural oscillations is found as a function of the plate length and the distance from the channel walls. The fields of pressure and gas velocities in the examined range of oscillations are constructed.
R. F. Shayakhmetova
Institute of Mechanics of Ufa Federal Research Center, Russian Academy of Sciences, Ufa, 450054, Russia
Keywords: газовая динамика, инвариантное решение, проективный оператор, уравнение Абеля, gas dynamics, invariant solution, projective operator, Abel equation
An invariant submodel of gas dynamics equations constructed on a three-dimensional subalgebra with a projective operator for the case of monatomic gas is under consideration. The submodel is reduced to an Abel equation, with integral curves constructed for it. For a separatrix of a saddle, an approximate solution is studied. Such solutions describe the vortex scattering of gas along plane curves placed on the surface of revolution.
G. V. Nosov1, M. G. Nosova2, Yu. Z. Vasil'eva1, E. O. Kuleshova1 1National Research Tomsk Polytechnic University, Tomsk, 634050, Russia 2Tomsk University of Control Systems and Radioelectronics, Tomsk, 634050, Russia
Keywords: магнитогидродинамический генератор, индуктивный накопитель, трансформатор, сверхпроводящая обмотка, рельсотрон, magnetohydrodynamic generator, inductive storage, transformer, superconducting winding, railgun
The power supply of an electromagnetic accelerator of solids (railgun) from a source of electromagnetic energy with a magnetohydrodynamic generator and a transformer with superconducting windings is calculated and analyzed. The laws and equations for electrical circuits are used, which are solved analytically and numerically. It is shown that a transformer with superconducting windings can be used to accumulate electromagnetic energy from a magnetohydrodynamic generator and to power a railgun in burst mode operation.
This paper considered the behavior of a semi-infinite ice cover on the surface of an ideal incompressible fluid of finite depth under the action of a load moving at a constant velocity along the edge of the cover at some distance from it. The ice cover is simulated by a thin elastic plate of constant thickness. In a moving coordinate system, the deflection of the plate is assumed to be steady. An analytic solution of the problem is constructed using the Wiener-Hopf technique. The wave forces, the deflection of the plate, and the elevation of the free surface of the fluid at different speeds of the load are considered.
P. E. Morozov
Institute of Mechanics and Engineering of the Kazan Scientific Center, Russian Academy of Sciences, Kazan, 420111, Russia
Keywords: полуаналитическое решение, лучевая система, горизонтальные скважины, анизотропный пласт, профиль притока, продуктивность, semi-analytical solution, radial system, horizontal wells, anisotropic reservoir, inflow profile, productivity
A semi-analytical method for determining the productivity of a radial system of horizontal wells in an anisotropic layer is proposed. Results of calculations of the productivity and distribution of fluid flow along the length of the wellbores of the radial system of horizontal wells using the proposed method are compared with the data of experimental studies based on electrolytic modeling and engineering calculations. The effects of the number of wellbores, their location in the reservoir, and the hydraulic pressure loss on the distribution of the fluid flow along the length of horizontal wellbores are investigated.
V. I. Zinchenko, V. D. Goldin, V. G. Zverev
Institute of Applied Mathematics and Mechanics, Tomsk, 634050, Russia
Keywords: гиперзвуковая скорость, аэродинамический нагрев, тепловая защита, сопряженный тепломассообмен, теплозащитные материалы, hypersonic velocity, aerodynamic heating, thermal protection, coupled heat and mass transfer, thermal protection materials
The problem of unsteady coupled heat and mass transfer in the course of motion of a spherically blunted conical body fabricated with the use of thermal protection materials is considered. Numerical integration is applied to study the characteristics of heat and mass transfer at constant stagnation parameters (Mach number 6, altitude 15 km, and flight time 600 s), which impose severe constraints on the choice of materials for thermal protection. It is demonstrated that the use of advanced ceramic materials ensures an admissible temperature regime and maintaining the initial geometry of the body, including its motion at an angle of attack.
The purpose of the present study is to investigate the heat transfer performance due to free convection of nanofluids with variable properties inside 2D and 3D channels with trapezoidal cross sections. The governing equations are solved numerically using the finite volume method and the SIMPLER algorithm. In this study, the effect of the nanoparticle volume fraction, Rayleigh number, side wall angles of the trapezoidal section, and axial slope of the 3D channel are examined. The presented results include the average Nusselt number, flow circulation streamlines, and isothermal contours. The heat transfer rate (i.e., Nusselt number) is seen to increase in both 2D and 3D channels with an increase in the Rayleigh number. In 2D trapezoidal enclosures, the Nusselt number decreases with an increase in the nanoparticle volume fraction from zero to 2% and increases if the nanoparticle volume fraction is greater than 2%. In 3D channels, an increase in the axial slope of the channel leads to an increase in the Nusselt number.
V. I. Smirnov1, Yu. V. Petrov2 1Emperor Alexander I St. Petersburg State Transport University, St. Petersburg, 198103, Russia 2Institute of Problems of Mechanical Engineering, Russian Academy of Sciences, St. Petersburg, 199178, Russia
Keywords: откол, инкубационное время, структурно-временной критерий, пороговый силовой импульс, импульсная емкость разрушения, spall, incubation time, structure-time criterion, threshold power pulse, pulse fracture capacity
This paper analyzes the effect of the time-dependent shape of a load pulse on the spall strength of materials. Within the framework of a classical one-dimensional scheme, triangular pulses with sections of signal increment and attenuation and without sections of signal increment are considered. Calculation results for the threshold characteristics of fracture for rail steel are given. The possibility of optimization of fracture by selecting a loading time with the use of an introduced characteristic of dynamic strength (pulse fracture capacity) is demonstrated. The study is carried out using a structure-time fracture criterion
A strength condition is obtained that takes into account the deformation anisotropy and the effect of uniform pressure on the mechanical properties of materials.
E. A. Gerasimenko1, L. V. Kovtanyuk1, A. A. Burenin2,3 1Institute of Automation and Control Processes, Far East Branch of the Russian Academy of Sciences, Vladivostok, 69004, Russia 2Institute of Engineering Science and Metallurgy, Far East Branch of the Russian Academy of Sciences, Komsomolsk-on-Amur, 681005, Russia 3Komsomolsk-on-Amur State Technical University, Komsomolsk-on-Amur, 681013, Russia
Keywords: большие деформации, упругость, вязкость, пластичность, ударная волна, волна разгрузки, large deformations, elasticity, viscosity, plasticity, shock wave, unloading wave
The one-dimensional dynamic problem of the interaction of the unloading wave with the elastic-plastic boundary is considered within the theory of large elastic-plastic deformations. It is shown that before the formation of the unloading wave, the increasing pressure gradient leads to quasistatic deformation of the elastic-viscoplastic material filling the round tube, which is retained in the tube due to friction about its wall, resulting in the formation of near-wall viscoplastic flow and an elastic core. The unloading wave is initiated at the moment when the material begins to slip on the inner wall of the tube. Calculations were conducted using the ray method of constructing approximate solutions behind strong discontinuity surfaces, and ray expansions of the solutions behind the cylindrical surfaces of discontinuities were obtained.
S. Siddharth, T. Senthilkumar
University College of Engineering, Tiruchirappalli, 620024, India
Keywords: точечная сварка трением с перемешиванием, алюминий, медь, усталость, оптимизация, fiction stir spot welding, aluminium, copper, fatigue, optimization
Friction stir spot welding is a new technique used in industries for spot joining dissimilar combinations. In this investigation, dissimilar combinations of Al5052 aluminium and C10100 copper are joined by using this technique with variations of important process parameters, such as the tool rotational speed, dwell duration, and plunging depth. A central composite design model is developed for establishing empirical relationships between the process parameters and the fatigue life of the joints (number of cycles to fracture). The analysis of variance is used for determining the significance of the developed model. The response surface methodology is used for maximizing the fatigue strength. By confirmation experiments, the model is validated, and the error is found to be within four percent.
A. F. Revuzhenko, O. A. Mikenina
Mining Institute, Siberian Branch, Russian Academy of Sciences, Novosibirsk, 630090, Russia
Keywords: горная порода, упругость, пластичность, самоуравновешенные напряжения, структурный параметр, rocks, elasticity, plasticity, self-balanced stresses, structural parameter
A closed mathematical model is formulated, which takes into account elastoplastic deformations and the medium capability of accumulating the energy of internal self-balanced stresses. Satisfaction of the diffeomorphism postulate (assumption of displacement field smoothness) is not required; as a result, the strains depend on the stresses and second derivatives of the stresses with respect to the coordinates. The model involves a linear structural parameter. Relations that take into account local bending of the elementary volumes of the medium are derived.
I. O. Gladkov1, A. M. Linkov1,2 1Institute for Problems in Mechanical Engineering, Russian Academy of Sciences, St. Petersburg, 199178, Russia 2Rzeszow University of Technology, Rzeszow, 35959, Poland
Keywords: гидроразрыв, плоская задача, контраст напряжений, hydraulic fracture, plane problem, stress contrast
A plane hydrofracture problem for the Khristianovich-Geertsma-de Klerk model is extended and solved in the case where a confining stress closing a fracture is not constant in the direction of its propagation. A method is developed for solving the problem with an arbitrary stress contrast. It is stated that the transition through a contact with positive (negative) contrast occurs with fracture arresting (acceleration), whose intensity is controlled by a dimensionless parameter derived from theoretical considerations and numerical results
V. K. Belov, L. P. Zheleznov, T. S. Ognyanova
Siberian Aeronautic Research Institute (SibNIA) named after S. A. Chaplygin, Novosibirsk, 630000, Russia
Keywords: некруговые цилиндрические композитные оболочки, дискретное подкрепление, нелинейное деформирование, устойчивость, метод конечных элементов, noncircular cylindrical composite shells, discrete reinforcement, nonlinear deformation, stability, finite element method
A previously developed technique is used to solve problems of strength and stability of discretely reinforced noncircular cylindrical shells made of a composite material with allowance for the moments and nonlinearity of their subcritical stress-strain state. Stability of a reinforced bay of the aircraft fuselage made of a composite material under combined loading with bending and twisting moments is studied. The effects of straining nonlinearity, stiffness of longitudinal ribs, and shell thickness on the critical loads that induce shell buckling are analyzed.
A. M. Il'yasov, G. T. Bulgakova
Ufa State Aviation Technical University, Ufa, 450008, Russia
Keywords: магистральная трещина, "сшитый" гель, вязкопластичная жидкость, устойчивость гелевого барьера, main crack, cross-linked gel, viscoplastic liquid, gel barrier stability
A quasi-one-dimensional nonstationary model for the waterproofing of main cracks using Herschel-Bulkley viscoplastic fluid is presented. The mathematical model developed in a one-dimensional isothermal approximation with the hydrodynamic parameters (pressure and velocity) averaged over the cross section of the crack can be used to determine the optimal technological parameters of the waterproofing process and the size of gel barriers to ensure their stability on exposure to an intense filtration flow after crack waterproofing. The ranges of flow rates which provide waterproofing of a crack of fixed width for the selected gel are determined. The stability of the established gel barriers is estimated.
This paper considers the dynamic problem of a semi-infinite crack in an elastic space that suddenly begins to grow with a constant speed. At the initial time, the crack faces at some distance from its tip are subjected to normal tensile concentrated forces which then move along the crack faces at a speed different from the speed of the crack tip. The stress intensity factor is calculated. Various special cases are examined.
V. M. Mirsalimov1,2 1Azerbaijan Technical University, Baku, AZ1073, Azerbaijan 2Institute of Mathematics and Mechanics, National Academy of Sciences, Azerbaijan, Baku, AZ1141, Azerbaijan
Keywords: круговой диск, смешанные граничные условия, трещины, функция перемещений точек границы диска, минимизация параметров разрушения, circular disk, mixed boundary conditions, cracks, displacement function of disk boundary points, fracture parameter minimization
Minimax criterion is used to carry out the theoretical analysis of normal displacement of points at the boundary of a circular disk weakened by arbitrarily placed rectilinear cracks. This paper presents a criterion and method for solving the problem of fracture of the circular disk with mixed conditions on its boundary. A closed system of algebraic equations is constructed, which allows for minimization of stress intensity factors. The normal displacement of points at the boundary of the circular disk, for which the bearing capacity of the disk increases.
The possibility of exerting control over the turbulent boundary layer on NACA 0012 wing section with the aim of improving the wing aerodynamic characteristics in incompressible flow is experimentally examined. Control over the boundary layer was exercised in the range of the angles of attack from -12 to 12° by implementing combined steady-state blowing/suction of air through a finely perforated surface located, respectively, on the windward and leeward side of the wing and presenting part of streamlined surface.
Using the differential turbulence model supplemented by the transport equation for the turbulent heat flux, a numerical study is carried out of the dependence of the Prandtl turbulent number on the molecular Prandtl number, the intensity of the gas injection (suction) through the permeable wall, and the freestream acceleration (deceleration). The air and mixtures of helium with xenon and argon are considered as gas carriers, and mercury, water, and transformer oil are used as liquid carriers. The obtained results of calculations are consistent with the available experimental data for the turbulent Prandtl number and the quantities included in its definition.
Experiments were performed on the influence of distributed injection of a heavy gas (elegas SF6) into the near-wall region of the supersonic (freestream Mach number М∞ = 2) boundary layer on its stability in relation to natural disturbances. Heavy gas injection for the case of linear development of disturbance field results in boundary layer stabilization. It was experimentally proved that the elegas injection can suppress disturbances at the frequencies higher than 15 kHz for the tested range of the streamwise coordinate.
Results of an experimental and numerical study of a supersonic flow over a model forward-facing step with a gas-permeable insert of variable porosity installed upstream of the step are reported. The free-stream Mach number was M = 2.0, 2.5, and 3.0, and the Reynolds number, Re = 5·105. The gas-permeable insert was either a section of a perforated plate or a section of a highly porous permeable cellular material. The flow visualization performed using the shadow method, PIV, and a soot-oil film has shown that the characteristic size of the vortical flow region exhibited a profound decrease on increasing the insert porosity. In numerical calculations performed at high values of that porosity, data on the displacement of the recirculation flow region into the porous material were obtained.
Symmetric and asymmetric self-similar flows of a viscous incompressible fluid along a semi-infinite right-angle dihedral corner with a preset streamwise pressure gradient have been considered. Equations describing such flows in the framework of boundary layer approximation have been derived. The asymptotic behavior of solutions of the derived equations far from the corner edge has been theoretically investigated. A new method of computation of these solutions has been developed. Solutions for two types of asymptotic behavior have been obtained.
The technology using for the replacement of damaged tissues the own cells of the patient, which are placed in a three-dimensional frame – scaffold, is promising for solving the problem of the bone tissue regeneration. A new biological reactor of the rotational type, in which the scaffold tissue rotates in a medium for cultivating the cells, was designed for the development of this technique. A numerical algorithm based on the ANSYS program was developed, which enables one to estimate in a new bioreactor the level of the mechanical load on the cells, which affects their properties. The algorithm enables the computation of the values of the shear stress and static pressure acting on the scaffold surface. The computations have shown that the necessary shear stress is reached in the proposed rotational bioreactor on the outer side of the inner cylinder (0.002-0.1 Pa) in the range of rotation frequencies 0.083 < f < 0.233 Hz. At the same time, computational results have revealed the presence of an inhomogeneity in the mechanical action distribution along the scaffold tissue, which is due to the appearance of two Taylor vortices with opposite rotation directions in the gap between the cylinders. The experiments on the flow field visualization inside the rotational biological reactor have shown a qualitative agreement of the flow character with computational results. The proposed numerical algorithm may simulate with sufficient accuracy the fluid flow in a real system. The obtained dependencies can be used in practice for creating an optimal microenvironment of the cells cultivated in the biological reactor.
Distribution of liquid velocity and its pulsations were measured in the space between fuel elements of the 7-rod experimental model of the fuel assembly of nuclear power plants at Reynolds numbers of 8000, 16000, and 24000. The influence of the spacer grid on distribution of the axial component of liquid velocity was determined. It is shown that the relative values of liquid velocity and its pulsations do not depend on the Reynolds number and they are determined by the distance from the spacer grid.
Dynamics of a liquid boiling on a heating element surface is investigated for the equivalent problem of dynamics of temperature of the fuel cell obtained in the concept of boiling curve. It has been shown that the structural instability of the potential of boiling curve leads to the need of studying the problem of temperature fluctuations of the surface on which boiling occurs. A theoretical analysis of the Itô's equation for the considered system model has shown that at a certain intensity of external random factors, the system passes from one state of self-organized criticality to another. These processes are accompanied by 1/fa– noise (flicker-noise), which is regarded as an objective indicator of the boiling crisis. The theoretical results of the work have been confirmed by experimental data of other authors.
The article presents the experimental dependences of a macro-contact angle and the diameter of a distilled water drop spreading over solid microstructured surface on surface average roughness (Ra) and fluid flow rate (G). It has been found that at changing G from 0.005 to 0.02 ml/s, the contact angle decreases, and at a liquid flow rate over 0.02 ml/s, it increases. With small values of G (0.005-0.01 ml/s), the drop diameter grows throughout the spreading process. In the range of G from 0.02 to 0.16 ml/s at the final stage of spreading, the contact line pinning, i.e., the diameter constancy, has been detected. The hypothesis about the mechanism of the pinning process has been formulated: it is due to the zero sum of all forces acting on the drop (inertia, viscosity, friction, gravity, and surface tension).
In this work, two-dimensional mixed convection and entropy generation of water-(Cu, Ag, Al2O3, and TiO2) nanofluids in a square lid-driven cavity containing two heat sources, have been numerically investigated. The upper lid and bottom wall of the cavity are maintained at a cold temperature TC, respectively. The governing equations along with boundary conditions are solved using the finite volume method. Comparisons with the previous results were performed and found to be in excellent agreement. The effects of the solid volume fraction, Rayleigh and Reynolds numbers, and different types of nanofluids on the total entropy generation St and on entropy generation due to heat transfer Sh are presented and discussed. Moreover, the heat sources positions have an effect on the total entropy generation and Bejan number. It was found that St and Sh
decrease with increase of f, Ra, and Re.
The influence of a thermal wake due to gas injection and due to a pulsating optical discharge (POD) on the aero-dynamic-drag force of a body in a supersonic air flow with Mach number M = 1.45 are experimentally examined. With the help of a single-component aerodynamic balance, the influence of the injected subsonic jet and the thermal wake produced by POD on the aerodynamic drag of a hemisphere-on-cylinder model was studied. It is shown that the observed aerodynamic-force reduction phenomenon can be made more pronounced by increasing the laser power and pulse repetition frequency, or by decreasing the distance between the model and the pulsating optical discharge. The maximum aerodynamic-force reduction (up to 15%) due to the thermal-wake action was observed at a maximum laser-radiation power of W = 2.3 kW and at a pulse rate of f = 90 kHz. The joint effect due to the argon jet and due to the POD caused an aerodynamic-drag force reduction reaching 30%.
Local features of thermophysical processes in the channels and pre-nozzle volumes of solid-propellant rocket engines with case-bonded charges of different cross-sectional shapes are considered. The influence of the charge shape on the heat exchange in the nozzle bottom is investigated. It is shown that the value of the Nusselt number at a critical point on the multi-nozzle bottom is determined both by the charge channel form and by the geometry of the pre-nozzle volume. By processing the numerical experimental results the criterial dependences for determining the Nusselt number in the areas of local increase of heat exchange intensity are obtained. The obtained dependences are compared with the known empirical formulas [1–4]. It is found that the use of empirical relationships to estimate the Nusselt number leads to incorrect determination of the parameters of heat transfer on the armored surfaces of the charge, the nozzle covers, and the input parts of the submerged rotating nozzle.
A class of nonlinear problems of non-stationary radiation-convective heat transfer under the conditions of microwave action with a small depth of penetration is considered in a forced laminar flow of liquid around a flat plane. The solutions to these problems are obtained using the effective asymptotic procedures at the successive stages of non-stationary and stationary radiation-convective heat transfer on the heat-radiating horizontal plane. The non-stationary and stationary stages of solution are matched using the “longitudinal coordinate-time” characteristic. The solutions constructed on such principles correlate reliably with the exact ones at the limiting values of such parameters as a small and large intensity of external thermal impact, small and large times, etc. The error of solutions does not exceed 1–7 %. As the plate is removed from the leading edge of the plate due to heat radiation, convective heat transfer degenerates from values characteristic of the boundary condition of the second kind to the values characteristic of the boundary condition of the first kind. A strong effect on the nature of variations of the surface temperature and Nusselt number of the complex parameter of microwave and thermal radiation is noted. An important advantage of the developed method for solving this class of external problems is that even before complex calculations it is possible to perform an exhaustive analysis of the fundamental laws of the processes under study. Despite a number of initial simplifications, the latter do not significantly affect the accuracy of results, guaranteeing reliable quantitative information. The developed method can also be extended to the regimes of forced convection with linear dependence of physical properties on temperature using transformation of A.A. Dorodnitsyn. To confirm adequacy of the constructed mathematical model, stationary radiation-convective heat transfer under the forced flow around a flat plate was studied experimentally. The results of comparison of the theoretical and experimental data show that they are in a good agreement. This again confirms the effectiveness of the developed method for constructing theoretical solutions to the nonlinear problems of forced convection using the asymptotic procedures.
This paper presents an analytical investigation of steady, fully developed MHD Couette flow of viscous, incompressible, electrically conducting fluid in the presence of radial magnetic field. Exact solutions are derived for the governing energy and momentum equations by taking into account the effects of viscous and Joule dissipations under relevant boundary conditions. The solutions obtained are graphically represented and the effects of various controlling parameters such as Hartmann number and Brinkman number on the temperature profile and consequently the Nusselt numbers are discussed. The significant result from the study is that increase in Hartmann number leads to enhancement on the Nusselt number at outer surface of inner cylinder while the role of Hartmann number is just reverse on Nusselt number at inner surface of outer cylinder. In addition, the Brinkman number has an insignificant effect on the Nusselt numbers when both surfaces are kept at equal temperature.
The paper presents a set of tests with a setup using steam supply into ejector instead of compressed air. Experiments measured the gas analysis data ¾ volumetric concentrations O2, CO, CO2, CnHm, NOx, H2 at different proportions of air and steam. The data are compared with calculations for thermodynamic equilibrium compositions for the reacting mixture С+Н2О+air performed by “Terra” computer code including the case of air excess (a £ 1). The cal-culations were also compared with available data on gasification output at a high content of ballasting gas. It was demonstrated that in these operation modes, the steam was an inert dilution agent, which did not exclude the outcome of coal gas production with high Н2 /СО and СО/СО2 ratios corresponding to different modes of gasification.
Mikhail Sergeevich Betekhtin1, Vladimir Yurievich Druzhinin2,3, Mikhail Albertovich Subotyalov4,3 1A.I. Evdokimov Moscow State University of Medicine and Dentistry, 20, Delegatskaya st., Moscow, 127473, Russia 2Novosibirsk State Medical University, 52, Krasny av., Novosibirsk, 630091, Russia 3Novosibirsk National Research State University, 2, Pirogov st., Novosibirsk, 630090, Russia 4Novosibirsk State Pedagogical University, 28, Vilyuyskaya st., Novosibisk, 630126, Russia
Keywords: история науки, дерматовенерология, лепра, Ригведа, Атхарваведа, протонаука, history of science, dermatovenereology, leprosy, the Rigveda, the Atharvaveda, protoscience
The article deals with poorly known issues of the history of dermatovenereology of the Vedic period in Ancient India. We present information found out in the Vedas, which are fundamental written source of this period. Close attention is paid to the Atharvaveda which contains information about the everyday life of Indians in general, as well as a description of their views on health, disease, pathogens and treatment tools in particular. Valuable information about skin diseases and treating them is contained in hymns of the Atharvaveda. For instance, they notice skin diseases and those of subcutaneous fatty tissue: lepra ( kuṣṭha ), palita , kilasa , apacit , and yaksma . We quote views of various commentators of ancient Indian texts on these diseases and on how they correspond to modern nosologic units. We present information about ancient Indians’ approaches to treating skin diseases by using various means: spells, natural factors, etc. The Atharvaveda contains hymns concerning cosmetic issues (means for intensifying hair growth) and treatment of external injuries. As to sexually transmitted diseases, the Atharvaveda contains no unequivocal information. Nevertheless, when studying ancient Indian texts, we found out hymns which noticed spells and medicinal herbs both for treating and provoking impotence. This information may indirectly refer to treatment of inflammatory diseases of the urogenital tract, including those of infectious etiology. The new information presented in the article enriches the history of medicine and contributes to the formation of a comprehensive picture of the development of global dermatovenereology.
Vladislav Georgievich Sokolov
The Unified Scientific Center for Space Thinking Problems, International Center of the Roerichs, 3/5, Maly Znamenskyla., Moscow, 119019, Russia
Keywords: научная школа, Шапошникова, Рерих, космическое мышление, космизм, Живая Этика, метаистория, Космос, культура, методология
For the first time in science, many aspects are systematically and systematically revealed: the main features of the scientific school are L.V. Shaposhnikova, her methodology, conceptual developments L.V. Shaposhnikova, who represent the structure of her scientific school.
Polad Shahmali oglu Geidarov
The Institute of Control Systems, National Academy of Sciences of Azerbaijan, 9, Bakhtiyar Vahabzadeh st. Baku, Az 1141, Azerbaijan
Keywords: электронная наука, реформы в науке, импакт фактор, индекс цитирования, научный семинар, защита диссертаций, нерецензируемые статьи, electronic science, reforms in science, impact factor, citation index, scientific seminar, presentation of a thesis, non-peer-reviewed articles
In recent years, the Internet offers services concerning publication of articles in scientific journals for a fee. Such business services appeared because of author’s wish for publishing their works in prestigious journals with high impact factors, as well as for publishing many articles quickly and artificially increasing their personal citation indexes (e.g., the H-index) in this way. Providing such a commercial service does not imply evaluating the quality and scientific level of articles which authors produced. As a result, methods of evaluating scientific works by using citation indexes become dubious. In this paper, we consider some schemes of publishing scientific works for a fee and possible ways of resisting such events. Besides, we analyze how citation indexes may influence publishing scientific works for a fee, as well as what and how effective control methods of disclosing and preventing such events may be. To resist paid publications, we propose to use an expertise system where experts perform their evaluation in the framework of electronic scientific seminar. We consider advantages of electronic scientific seminar as a means of eliminating the very phenomenon of paid publications over other approaches. In addition, we describe the necessary conditions for creating an electronic scientific seminar system and ensuring a high quality decision making basing on expertise.
