O. A. Frolovskaya
Lavrent'ev Institute of Hydrodynamics, Siberian Branch, Russian Academy of Sciences, Novosibirsk, 630090, Russia
Keywords: нестационарность, автомодельность, критическая точка, unsteadiness, self-similarity, critical point
The problem of unsteady viscous incompressible fluid flow near a critical point is considered. Self-similar solutions describing plane and axisymmetric flows are constructed.
E. N. Zhuravleva
Lavrent'ev Institute of Hydrodynamics, Siberian Branch, Russian Academy of Sciences, Novosibirsk, 630090, Russia
Keywords: течение вязкой несжимаемой жидкости, уравнения Навье -- Стокса, течения со свободными границами, инвариантные и частично инвариантные решения, численные решения, incompressible viscous fluid, Navier-Stokes equations, free-boundary flows, invariant and partially invariant solutions, numerical solutions
This paper presents a numerical study of the partially invariant solutions of the Navier-Stokes equations for the plane case which describes unsteady flow in a layer bounded by a straight solid wall and a free boundary parallel to it. It is found that for different values of the initial flow velocity, there may be the establishment a steady state with a decrease or an increase in the initial layer thickness can be established or the layer thickness can be increased infinitely due to liquid inflow from infinity.
The geometry of flows resulting from separation of hanging drops of liquids with significantly different physical properties (alcohol, water, glycerin, oil) was studied by high-speed video recording. The dynamics of the processes is studied for characteristic shapes of bridges: with slightly nonuniform thickness and with thinning of the upper and lower ends. It is shown that the change of the shape of the separated bridge has a number of stages determined by the properties of the liquid. As a result, the bridge is transformed into a small droplet - a satellite droplet.
Q. Huang1, J. Tang2, L. Zhang2, K. Ouyang3 1Yancheng Institute of Technology, Yancheng, 22405, China 2Hunan University, Changsha, 410082,China 3State Grid Hunan Electric Power Corporation Research Institute, Changsha, 410007, China
Keywords: обобщенное уравнение Бюргерса -- Фишера, неравновесный фазовый переход, бифуркационное решение, формирование шаблона, generalized Burgers-Fisher equation, nonequilibrium phase transition, bifurcation solution, pattern formation
A nonequilibrium phase transition of a generalized Burger-Fisher equation describing biological pattern formation with a periodic boundary condition is examined. In the presence of a weak external force, some approximate bifurcation solutions near a critical point and new spatially periodic patterns are obtained by using the perturbation method in an infinite-dimensional space. The result shows that the external force delays the bifurcation.
D. V. Sadin, V. M. Varvarskii
Alexander Mozhaysky Military Space Academy, St. Petersburg, 197198, Russia
Keywords: истечение в вакуум, газодисперсная среда, жесткость уравнений, TVD-схема, exhaustion into vacuum, gas--particle mixture, stiffness of equations, TVD scheme
Two-dimensional unsteady exhaustion of a one-velocity gas-particle mixture into vacuum is analyzed in extreme equilibrium cases of heat transfer. Domains of existence of a one-dimensional Riemann wave and side expansion wave and the boundary of the expansion region are obtained. In the case of temperature equilibrium, the reverse flow is found to occupy a large region extending beyond the boundaries defined by the angles of expansion of an ideal gas and a gas-particle mixture with thermally insulated phases. Exhaustion of a nonequilibrium two-phase medium in terms of velocities and temperatures into vacuum is numerically simulated. It is demonstrated that a barrel structure with wavy expansion of the gas and combined discontinuities in the expanding gas-particle mixture is formed.
M. A. Pakhomov, V. I. Terekhov
Kutateladze Institute of Thermophysics, Siberian Branch, Russian Academy of Sciences, Novosibirsk, 630090, Russia
Keywords: газожидкостный поток, моделирование, структура течения, турбулентность, gas-liquid flow, simulation, flow structure, turbulence
Results of simulations of the flow structure in a vertical monodisperse gas-liquid flow in a tube on the basis of the Euler approach with allowance for the effect of bubbles on the averaged characteristics and turbulence of the carrier flow are reported. The carrier phase turbulence is calculated by using the transport model for the Reynolds stress tensor components. A comparison of the simulation results with available experimental data shows that the proposed apprach provides an adequate description of turbulent bubble flows in wide ranges of the local gas content and gas inclusion sizes.
Yu. G. Krat, I. I. Potapov
Computing Center, Far Eastern Branch, Russian Academy of Sciences, Khabarovsk, 680000, Russia
Keywords: напорный канал, донные волны, математическая модель, pressure conduit, bottom waves, mathematical model
The problem of the stability of the sandy bottom surface in a rectangular pressure conduit with respect to spatially one-dimensional perturbations. The problem of bed stability is solved using an analytical formula of sediment discharge which takes into account the effect of bottom pressure on sediment movement. An analytical relationship of the bottom wavelength to the hydrodynamic flow parameters and the diameter of bottom particles is obtained and compared with experimental data.
M. Bilal Ashraf1, T. Hayat2,3, S. A. Shehzad4, H. Malaikah3 1COMSATS Institute of Information Technology, Kant 47,070 Wah, Pakistan 2Quaid-i-Azam University, 45320, Islamabad 44000, Pakistan 3Nonlinear Analysis and Applied Mathematics (NAAM) Research Group, Islamabad 44000, Pakistan 4King Abdulaziz University, Jeddah 21589, Saudi Arabia
Keywords: вязкоупругая жидкость, экспоненциально растягивающаяся поверхность, теплообмен, viscoelastic fluid, exponentially stretching surface, heat transfer
An analysis of a three-dimensional viscoelastic fluid flow over an exponentially stretching surface is carried out in the presence of heat transfer. Constitutive equations of a second-grade fluid are employed. The governing boundary layer equations are reduced by appropriate transformations to ordinary differential equations. Series solutions of these equations are found, and their convergence is discussed. The influence of the prominent parameters involved in the heat transfer process is analyzed. It is found that the effects of the Prandtl number, viscoelastic parameter, velocity ratio parameter, and temperature exponent on the Nusselt number are qualitatively similar.
A 3D numerical study of convective instabilities in a horizontal liquid layer (silicone oil with a Prandtl number Pr = 102) with an upper free surface is presented. The liquid layer is subjected to an inclined gradient of temperature. The influence of both gravity and thermocapillary forces on the formation of convective patterns is studied for different values of the liquid layer depth. Numerical results are found to be in good agreement with experimental data of other authors.
An axisymmetric magnetohydrodynamic (MHD) boundary layer flow and heat transfer of a fluid over a slender cylinder are investigated numerically. The effects of viscous dissipation, thermal radiation, and surface transverse curvature are taken into account in the simulations. For this purpose, the governing partial differential equations are transformed to ordinary differential equations by using appropriate similarity transformations. The resultant ordinary differential equations along with appropriate boundary conditions are solved by the fourth-order Runge-Kutta method combined with the shooting technique. The effects of various parameters on the velocity and temperature profiles, local skin friction coefficient, and Nusselt number are analyzed.
G. Palani1, E. J. L. Kumar2, K.-Y. Kim3 1Dr.Ambedkar Govt. Arts College, Chennai, 600039, Tamil Nadu, India 2SRM Arts and Science College, Tamil Nadu, India 3Inha University, Incheon, 402-751, Republic of Korea
Keywords: свободная конвекция, изменяющиеся вязкость и теплопроводность, вертикальный конус, free convection, variable viscosity and thermal conductivity, vertical cone
The present paper deals with a flow of a viscous incompressible fluid along a heated vertical cone, with due allowance for variations of viscosity and thermal diffusivity with temperature. The fluid viscosity is assumed to be an exponential function of temperature, and the thermal diffusivity is assumed to be a linear function of temperature. The governing equations for laminar free convection of the fluid are transformed into dimensionless partial differential equations, which are solved by a finite difference method with the Crank-Nicolson implicit scheme. Dependences of the flow parameters on the fluid viscosity and thermal conductivity are obtained.
This paper presents an analysis of the possibility of increasing the ultimate elongation and penetration capability of metallic shaped-charge jets in the presence of an axial magnetic field in the shaped-charge liner by the heating and thermal softening of the jet material due to a sharp increase in the magnetic-field induction in the jet formation region upon liner collapse. This process is studied by numerical simulation in a quasi-two-dimensional formulation taking into account the inertial extension of the conductive rigid-plastic rod in the presence of a longitudinal magnetic field in it.
V. D. Kurguzov, A. G. Demeshkin
Lavrentiev Institute of Hydrodynamics, Siberian Branch, Russian Academy of Sciences, Novosibirsk, 630090, Russia
Keywords: тонкие пленки, отслоение, упругое основание, потеря устойчивости, нелинейное деформирование, thin films, detachment, elastic foundation, buckling, nonlinear strain
The processes of elastic strain of thin films under mechanical load are considered. The film is simulated by a longitudinally compressed plate placed on an elastic foundation. The computer model of the buckling of the narrow thin plate with a detachment portion, placed on an elastic foundation is constructed. The supercritical behavior of the plate - substrate system is studied. The experiments on the axial compression of the metal strip adhered to the rubber plate are performed, and 2 to 7 buckling modes are obtained therein. The critical loads and buckling modes obtained in the numerical calculations are compared with the experimental data. The possibility of progressive detachment of the metal plate from the foundation in excess of the critical load is shown. It is found that the use of the proposed approach, which, in contrast to other approaches, takes into account the elastic strain of the substrate, causes the dependence of critical bending stresses on the stiffness of the foundation.
I. A. Banshchikova, V. A. Blinov
a:2:{s:4:"TYPE";s:4:"TEXT";s:4:"TEXT";s:112:"Lavrent’ev Institute of Hydrodynamics, Siberian Branch, Russian Academy of Sciences, Novosibirsk, 630090, Russia";}
Keywords: пластина, ползучесть, трансверсально-изотропный материал, кручение, плоское напряженное состояние, plate, creep, transversely isotropic material, torsion, plane stress
This paper presents the results of calculations and experiments on the torsion of plates made of isotropic and transversely isotropic BT-20 and 1163T alloys with reduced resistance to creep strain in the direction perpendicular to the median surface. The numerical modeling results for plates of different thickness that belong to the class of rigid and flexible plates made with the use of the pure bending theory and the finite element method are compared. It is established that during the deformation of the plate of anisotropic material into an alternating saddle-shaped surface, the curvature values are smaller than in the case of a plate of a isotropic material. The calculation carried out ccording to the pure bending theory yields an upper estimate of the curvature ifference during the strain of the plates of transversely isotropic and sotropic materials.
a:2:{s:4:"TYPE";s:4:"TEXT";s:4:"TEXT";s:59:"М. М. Abaiee, M. J. Ketabdari, А. Ahmadi, H. Alemi Ardakani";}
Amirkabir University of Technology, Tehran, Iran
Keywords: платформа с натяжными опорами типа "морская звезда", модельное исследование, метод граничных элементов, модифицированный метод Эйлера, дифракция, излучение, sea-star TLP, model test, BEM, MEM, diffraction, radiation
This paper describes an experimental work on a 1:100 scaled model of a miniature sea-star tension leg platform (TLP) in a wave flume. Two different numerical models are developed: finite element model (FEM) based on the Morison equation and boundary element model (BEM) based on a 3D diffraction/radiation theory. The developed codes are used to calculate hydrodynamic forces and related coefficients. The nonlinear hull/tendon coupled dynamic equation of a mini sea-star TLP is solved by using a modified Euler method (MEM). The results of numerical modeling of the motion response behavior of the platform in different degrees of freedom are compared with experimental data. This comparison shows good agreement between the results. Furthermore, this modeling reveals that the first-order diffraction method and quasi-static tendon modeling are sufficient in general for the hydrodynamic analysis of the sea-star TLP.
Instability of a thin-walled stainless steel tube with a crack-shaped defect under combined loading is studied in this paper. Furthermore, the effects of the tube length, crack orientation, and crack length on the buckling behavior of tubes are investigated. The behavior of tubes subjected to combined is analyzed by using the finite element method (by Abaqus software). For cracked tubes with a fixed thickness, the buckling load decreases as the tube length and the ratio of the tube length to its diameter increase. Moreover, the buckling load of cracked tubes under combined loading also decreased with increasing crack length.
A mixed convection flow of a third-grade fluid near the orthogonal stagnation point on a vertical surface with slip and viscous dissipation effects is investigated. The governing partial differential equations for the third-grade fluid are converted into a system of nonlinear ordinary differential equations by using a similarity transformation. The effects of various parameters, including the Weissenberg number, third-grade parameter, local Reynolds number, Prandtl number, Eckert number, mixed convection parameter, velocity slip, and thermal slip on the velocity and temperature profiles, local skin friction coefficient, and local Nusselt number are discussed.
E. Yu. Vitokhin, M. B. Babenkov
St. Petersburg State Polytechnic University, St. Petersburg 195251, Russia
Keywords: гиперболическая задача термоупругости, закон Максвелла -- Каттанео, релаксация теплового потока, метод конечных разностей, hyperbolic thermoelastic problem, Maxwell-Cattaneo law, heat flow relaxation, finite difference method
The thermoelastic problem of laser effect on metals and dielectrics is studied taking into account the finite speed of propagation of thermal waves and using a numerical finite-difference algorithm. The resulting numerical solution is compared with the analytical one. The problem is solved in coupled and uncoupled formulations. The solutions of the hyperbolic thermoelastic problem are compared with the solutions of the classical problem. Analytical expressions are obtained for the propagation speeds of the thermoelastic wave components. Times are determined at which the difference between the solutions of the hyperbolic and classical thermoelastic problems can be detected experimentally.
V. O. Shemelina
Lavrent'ev Institute of Hydrodynamics, Siberian Branch, Russian Academy of Sciences, Novosibirsk, 630090, Russia
Keywords: изгибно-гравитационные колебания, собственные колебания, гидроупругость, мелкая вода, круглая пластина, flexural-gravitational vibrations, natural vibrations, hydroelasticity, shallow water, circular plate
Numerical and analytical studies of the natural and quasi-natural flexural-gravitational vibrations of an elastic plate floating on a liquid surface are performed based on shallow-water long-wave theory. Dependences of natural and quasi-natural frequencies on the geometrical parameters of the vibration region are studied for the cases of bounded and unbounded reservoirs. The effect of bottom irregularities in the form of a circular cylinder or a circular truncated cone on the natural and quasi-natural frequencies and functions is studied.
This paper describes the effect of thermal exposition (high temperature soak) (T=675oC) on the relaxation of residual creep stresses in the surface reinforced solid cylindrical sample of a ZhS6UVI alloy. The analysis is performed with the use of experimental data for the residual stresses after reinforcement by microspheres and after high-temperature soaks T=675oC for 50, 150, and 300 h. The paper describes the solution technique for the boundary-value problem of creep of the reinforced cylindrical sample with the initial stress-strain state in thermal exposition. The uniaxial experimental creep curves obtained at constant stresses of 500, 530, 570, and 600 MPa to construct models describing the first and second stages of creep. The calculated and experimental data for the longitudinal (axial) component of the residual stress tensor are compared, and it is found that they are in satisfactory agreement
E. P. Dats1, A. V. Tkacheva2 1Vladivostok State University of Economics and Service, Vladivostok, 690990, Russia 2Institute of Engineering and Metallurgy, Far Eastern Branch, Russian Academy of Sciences, Komsomolsk-on-Amur, 681005, Russia
Keywords: упругость, пластичность, температурные напряжения, горячая посадка, остаточные напряжения, elasticity, plasticity, thermal stresses, shrink fit, residual stresses
This paper presents a solution of a sequence of one-dimensional boundary-value problems of thermal stresses defining the elastic-plastic deformation processes used in the shrink fitting of cylindrical bodies. The origin and development of plastic flow in the materials of the assembly elements are studied taking into account the temperature dependence of the yield strength of these materials. During temperature equalization, the flow can slow down, followed by unloading and formation of a residual stress field providing an interference fit. The conditions of formation and motion of the boundaries of the elastic and plastic states in both plastic flow and during unloading are determined.
A. V. Fedorov, A. V. Shulgin
Khristianovich Institute of Theoretical and Applied Mechanics, Siberian Branch, Russian Academy of Sciences, Novosibirsk, 630090 Russia
Keywords: молекулярная динамика, наночастицы, плавление, теплоемкость, теплопроводность, molecular dynamics, nanoparticles, melting, specific heat, thermal conductivity
Molecular dynamics simulations of melting of aluminum nanoparticles are performed with the use of the DL_POLY software package and embedded atom potential method for determining the thermal conductivity. Analytical approximations for the dependences of the thermal conductivity and specific heat on the temperature and particle size are reported. Based on the thermophysical parameters obtained in the study, the problem of nanoparticle melting is solved within the framework of the phenomenological approach.
D. A. Yagodnikov1, A. V. Voronetskii1, V. I. Sarab'ev2
a:2:{s:4:"TEXT";s:202:"1Bauman Moscow State Technical University, Moscow, 105005 Russia 2Federal Research and Production Center “Research Institute of Applied Chemistry”, Sergiyev Posad, 141313 Russia";s:4:"TYPE";s:4:"html";}
Keywords: горение, наноразмерный диборид алюминия, пиротехнический состав, воздух, двухзонный рабочий участок, полнота сгорания, combustion, nanoscale aluminum diboride, pyrotechnic composition, air, dual-zone working region, combustion efficiency
This paper presents the experimental study of ignition and combustion of micro- and nanoparticles of aluminum diboride as part of pyrotechnic energy-saturated compositions in a gas generator with an air afterburner chamber and the thermodynamic calculations of combustion of pyrotechnic compositions based on aluminum diboride in air. The discharge of the combustion products from the afterburner chamber is recorded on video. It is shown that replacing micron aluminum diboride by powdered diboride with a mass-average diameter of particles equal to ≈270 nm in the pyrotechnic composition and increasing the pressure in the afterburner chamber cause the combustion efficiency in air to increase by 5–20%.
B. S. Seplyarskii, N. A. Kochetov, R. A. Kochetkov
Institute of Structural Macrokinetics and Materials Science, Russian Academy of Sciences, Chernogolovka, 142432 Russia
Keywords: горение, механическая активация, скорость горения, поток газа, кондуктивный теплообмен, лучистый теплообмен, combustion, mechanical activation, burning rate, gas flow, conductive heat transfer, radiant heat transfer
This paper describes a study on the burning of pressed and bulk-density samples from a Ni + Al mixture subjected to mechanical activation. It is shown that mechanical activation and dispersion have a different impact on the burning rate of the samples under study. The gas flow hardly changes the burning rate of the bulk-density mixtures. The linear burning rate of the dispersed bulk-density mixture is 1.7 times greater than that of the pressed mixture, and the mass burning rates are equal to each other. The calculations showed that the conductive heat transfer mechanism in the combustion wave of the dispersed bulk density mixture is the principal mechanism.
V. G. Prokof'ev1, V. K. Smolyakov1,2 1Tomsk State University, Tomsk, 634050 Russia 2Department of Structural Macrokinetics, Tomsk Scientific Center, Siberian Branch, Russian Academy of Sciences, Tomsk, 634021 Russia
Keywords: безгазовое горение, спиновый режим, фазовый переход, gasless combustion, spin mode, phase transition
The thermal effect of the phase transition on unstable regimes of gasless combustion is numerically studied within the framework of the model of solid flame combustion of a cylindrical sample. The closer the phase transition temperature to the burning temperature, the more pronounced the effect of the phase transition on the combustion character. In this case, the combustion front surface is noticeably smoothed owing to reduction of temperature gradient values. A relationship between the change in the combustion modes considered in the study and the change in the phase transition parameters is found. An unsteady periodic symmetric mode of combustion with ring-shaped trajectories of motion of combustion sites over the side surface is obtained.
V. M. Kislov, S. V. Glazov, E. A. Salgansky, Yu. Yu. Kolesnikova, M. V. Salganskaya
Institute of Problems of Chemical Physics, Russian Academy of Sciences, Chernogolovka, 142432 Russia
Keywords: фильтрационное горение, газификация, уголь, энергетика, твердое топливо, filtration combustion, gasification, coal, power, solid fuel
This paper presents the results of a numerical and experimental study of gasification of carbonaceous materials in the filtration combustion mode using mixtures of air with CO2 as an oxidizer. The results obtained are compared with the results on gasification of carbonaceous materials by a steam-air mixture. It is shown that the replacement of steam in the gaseous oxidizer by an equal volume CO2 leads to a marked reduction in the combustion temperature. The maximum calorific values of the product gas in coal gasification by a mixture of air and CO2 are close to the values obtained for steam-air gasification.
M. Yu. Chernetskiy1,2, A. P. Burdukov1, E. B. Butakov1, I. S. Anufriev1, P. A. Strizhak3 1Kutateladze Institute of Thermophysics, Siberian Branch, Russian Academy of Sciences, Novosibirsk, 630090 Russia 2Siberian Federal University, Krasnoyarsk, 660074 Russia 3Tomsk Polytechnical University, Tomsk, 634050 Russia
Keywords: воспламенение, горение, пылеугольное топливо, механоактивация, дезинтегратор, кинетические константы, ignition, combustion, coal dust fuel, mechanical activation, disintegrator, kinetic constants
Experiments aimed at studying the ignition of coal dust obtained by coal disintegration in high-energy mills are performed in a tubular furnace. Effective kinetic constants of ignition of coal dust ground in a vibrational-centrifugal mill and in a disintegration mill under conditions of rapid heating are determined for the first time. It is shown that the volatile release rate depends on the method of coal grinding.
V. M. Mochalova1,2, A. V. Utkin1,2, S. M. Lapin1,3 1Institute of Problems of Chemical Physics, Russian Academy of Sciences, Chernogolovka, 142432 Russia 2Tomsk State University, Tomsk, 634050 Russia 3Lomonosov Moscow State University, Moscow, 119991 Russia
Keywords: детонация, химпик, структура детонационной волны, время реакции, нитрометан, диэтилентриамин, волны срыва реакции, критический диаметр, detonation, chemical spike, detonation wave structure, reaction time, nitromethane, diethylenetriamine, reaction disruption wave, critical diameter
This paper presents the results of an experimental determination of the width of the reaction zone in a detonation wave in nitromethane sensitized by diethylenetriamine. It was found that increasing the mass concentration of diethylenetriamine from 0 to 2.0% reduced the typical reaction time by a factor of less than two while the critical diameter decreased by an order of magnitude. This discrepancy is explained by the fact that the critical detonation diameter of neat nitromethane is determined not by the reaction time but by flow instability at the edge of the charge, manifested in the occurrence of a wave of reaction disruption. Increasing the initial rate of nitromethane decomposition by addition of diethylenetriamine leads to flow stabilization and thus to a change in the nature of the critical diameter.
L. Tan1, L.-H. Xia1, Q.-J. Wu1,2, S. Xu1,2, D.-B. Liu1 1School of Chemical Engineering, Nanjing University of Science and Technology Nanjing, 210094, Jiangsu, China 2National Quality Supervision and Inspection Center for Industrial Explosive Materials, Nanjing, 210094, Jiangsu, China
Keywords: нитрат аммония, хлорид калия, моноаммонийфосфат, скорость детонации, ammonium nitrate, potassium chloride, monoammonium phosphate, detonation velocity
To better understand the detonation characteristics of ammonium nitrate (AN) and activated additives mixtures, potassium chloride (KCl) and monoammonium phosphate (MAP) are mixed with AN by different mixing methods. The UN gap test and scanning electron microscopy are applied to study AN and AN-additive mixtures. For the mechanical mixing method, the detonation velocity of AN-additives decreases with increasing the additive proportion, while the detonation velocity of modified AN prepared by the solution mixing method shows the opposite tendency. It is proved that the sensitivity to shock waves increases as the size of AN particles decreases. The type of additives, the mixing methods, and the particle size distribution are important parameters that affect the detonation characteristics of AN.
An underwater explosion test is used to determine the detonation properties of metallized explosives containing aluminum and boron powders. An oxygen bomb calorimeter (PARR 6200 calorimeter, Parr Instrument Company, USA) is used to obtain the heat of combustion of the metal mixtures. As the content of boron powders is increased, the heat of combustion of the metal mixtures increases, and the combustion efficiency of boron decreases. The highest value of the combustion heat is 38.2181 MJ/kg, with the boron content of 40%. All metallized explosive compositions (RDX/Al/B/AP) have higher detonation energy (including higher shock wave energy and bubble energy) in water than the TNT charge. The highest total useful energy is 6.821 MJ/kg, with the boron content of 10%. It is 3.4% higher than the total energy of the RDX/Al/AP composition, and it is 2.1 times higher than the TNT equivalent.
S. M. Karakhanov1, A. V. Plastinin1, D. S. Bordzilovskii2, S. A. Bordzilovskii1,3 1Lavrentyev Institute of Hydrodynamics, Siberian Branch, Russian Academy of Sciences, Novosibirsk, 630090 Russia 2Institute of Laser Physics, Siberian Branch, Russian Academy of Sciences, Novosibirsk, 630090 Russia 3Novosibirsk State University, Novosibirsk, 630090 Russia
Keywords: ударные волны, микробаллоны, коллапс поры, горячие точки, вязкость, shock wave, microballoons, pore collapse, hot spots, viscosity
The optical thermal radiation arising from the shock collapse of glass or polymer microballoons in a transparent condensed medium (water or polymerized epoxy resin) was detected. The temporal characteristics of the detected radiation in the pressure range 0.5–29 GPa at different viscosities of the material surrounding the pore were determined. The brightness temperature of hot spots was estimated to be 1600–3200 K at a pressure of 2–29 GPa. The length of the leading edge of the radiation pulse corresponding to the time of hot-spot formation increases from 2·10–8 to 30·10–8 s, depending on the shock-wave intensity and the viscosity of the material surrounding the pore. Analysis of the data shows that in the pressure range 5–29 GPa, hot-spot formation is dominated by the hydrodynamic mechanism of collapse and in the range 0.5–5 GPa, by the viscoplastic mechanism.
a:2:{s:4:"TEXT";s:89:"V. V. Sil'vestrov†1, A. V. Plastinin1, A. S. Yunoshev1,2";s:4:"TYPE";s:4:"html";} 1Lavrentyev Institute of Hydrodynamics, Siberian Branch, Russian Academy of Sciences, Novosibirsk, 630090 Russia 2Novosibirsk State University, Novosibirsk, 630090, Russia
Keywords: эмульсионная матрица, ударное инициирование, сверхдетонационное давление, emulsion matrix, shock initiation, superdetonation pressure
A pure emulsion based on an aqueous solution of ammonium nitrate placed in a steel tube 114 mm in inner diameter was shock loaded. The achieved dynamic pressure of 30 GPa, far exceeding the calculated detonation pressure, did not lead to the development of an explosive process.
The analysis of the dynamic response of a circular tunnel in three types of soil at different depths under surface detonation of a 250-kg TNT charge reveals that the tunnel peak particle velocity and the failure zone length are sensitive to the soil type and material properties. The buried tunnel in silty clay sand has the least damage; the length of the failure zone is 5 m in the longitudinal direction and 0 to 60oC at the top arch.
F. A. Bykovskii, S. A. Zhdan, E. F. Vedernikov
Lavrentyev Institute of Hydrodynamics, Siberian Branch, Russian Academy of Sciences, Novosibirsk, 630090 Russia
Keywords: непрерывная спиновая детонация, керосин, воздух, водород, поперечные детонационные волны, кольцевая камера сгорания, continuous spin detonation, kerosene, air, hydrogen, transverse detonation waves, annular combustor
Regimes of continuous spin detonation of two-phase kerosene-air mixtures with small addition of hydrogen are obtained for the first time in a flow-type annular cylindrical combustor 503 mm in diameter.
V. V. Turovtsev1, E. M. Chernova1, V. N. Sitnikov1, V. N. Emel'yanenko2, Yu. D. Orlov1 1Tver State University, Rostov-on-Don, Russia 2Kazan Federal University, Rostov-on-Don, Russia
Keywords: квантовая теория атомов в молекуле, электронная плотность, сопряжение, пропаргил, энтальпия образования, энтальпия разрыва связи, quantum theory of atoms in molecules, electron density, conjugation, propargyl, enthalpy of formation, enthalpy of bond cleavage
By means of B3LYP/6-311++G(3df,3pd) the electron density distribution in the propargyl radical CH2CCH is obtained. Within the Quantum Theory of Atoms in Molecules the phenomenon of conjugation and the spin density distribution of the unpaired electron in CH2CCH are studied at the qualitative level. Characteristics of the electronic structure of CH2CCH and its parent molecules CH3-C≡CH and CH2=C=CH2 are compared. With the use of the rigid rotator-anharmonic oscillator model the thermodynamic properties of the propargyl radical and enthalpies of bond cleavage in propyne and allene are calculated in the temperature range 298-1500 K. The relationship between the electronic and thermodynamic properties of CH2CCH is considered and its conjugation energy is calculated.
N. N. Kharabayev1, A. G. Starikov1,2, V. I. Minkin1,2 1Southern Federal University, Rostov-on-Don, Russia 2Southern Scientific Center, Rostov-on-Don, Russia
Keywords: квантовая химия, молекулярная структура, хелатные комплексы металлов, ароматические азометины, quantum chemistry, molecular structure, metal chelate complexes, aromatic azomethines
Within density functional theory the experimentally observed stereoeffects of the ligand environment in low-spin bis-chelates of Ni(II), Pd(II), and Pt(II) with aromatic azomethines is modeled. It is shown that complexes with the MN2O2 coordination core are characterized by the trans -configuration and in complexes with MN2S2 or MN2Se2 cores the stabilization of the cis -configuration occurs. The relationship is found between the composition of metal cycles and their conformation (an inflection along the donor atom line), the degree of steric hindrances in the cis -configuration due to the interligand interaction of R substituents at azomethine nitrogen atoms and the relative stability of cis - and trans -isomers of the complex.
E. L. Krasnykh, S. V. Portnova
Samara State Technical University, Samara, Russia
Keywords: энтальпия испарения, топологический индекс, индекс связанности, сложные эфиры, прогнозирование, enthalpy of evaporation, topological index, connectivity index, esters, prediction
In the work a prediction method based on modified Randic indices to estimate the enthalpies of vaporization under standard conditions Dvap H 0(298.2) is proposed for esters with different structures and numbers of ester groups. It is shown that the proposed method enables the prediction of enthalpies of vaporization of esters with an accuracy as good as experimental.
D. V. Korabel'nikov, Yu. N. Zhuravlev
Kemerovo State University, Kemerovo, Russia
Keywords: нитрат, перхлорат, комплексный катион, кристаллическая структура, химическая связь, электронные состояния, nitrate, perchlorate, complex cation, crystal structure, chemical bond, electronic states
Based on density functional theory with regard to the dispersion interaction the crystal structure and electronic properties of C4H8N12O6 and C4H8N10Cl2O8 are studied. Atomic structural parameters, bond populations, atomic charges, energy and spatial electron distributions are calculated. Differences in the studied characteristics caused by the non-equivalence of atoms are shown. A partially covalent nature of anion-cation bonds is revealed. The cationic nature of the lower unoccupied states is established, which results in a small band gap of ~1.7 eV as compared to other nitrates and perchlorates.
Ab initio calculations are employed to investigate nitrogen inversion as a configuration change that can supply an extremely useful switchable control mechanism for some complex systems. In this paper, the design of a new artificial rotary molecular machine based on nitrogen inversion is discussed. The introduced design of a molecular rotator is based on the reciprocating motion of a substituent due to the inversion phenomenon, leading to the rotary motion in the molecule. Since simple secondary amines easily face the inversion process at room temperature, aziridine is selected as the initial driver for the molecular motion. The most obvious finding from this study is that, following the displacement of the substituent attached to the aziridine nitrogen atom, two rotary motions occurr in the molecule, one clockwise and another counterclockwise with a 39.52 to 150.09° angle domain.
A. A. Ryadun, V. A. Trifonov, V. A. Nadolinny, A. A. Pavlyuk, M. I. Rakhmanova
Nikolaev Institute of Inorganic Chemistry, Siberian Branch, Russian Academy of Sciences, Novosibirsk, Russia
Keywords: ЭПР ионов переходных металлов, люминесценция, сцинтилляторы, кристаллы двойного молибдата, EPR of transition metal ions, luminescence, scintillators, crystals of double molybdate
By the low-gradient Čzochralski method, both undoped and copper ion activated Li2-2 xMg2+ x(MoO4)3 crystals are grown. The charge state and structural position of impurity copper ions are determined using EPR. Investigations of the luminescence properties reveal that luminescence with a maximum at λ = 520 nm is observed for Li2-2 xMg2+ x(MoO4)3 crystals. A decrease in the temperature increases the intensity of this luminescence. It is found that the doping of Li2-2 xMg2+ x(MoO4)3 crystals with copper ions also increases the luminescence intensity with a maximum at λ = 520 nm. It is supposed that cation vacancies, which provide the charge compensation when copper ions substitute for lithium ions, are responsible for the luminescence.
