Publishing House SB RAS:

Publishing House SB RAS:

Address of the Publishing House SB RAS:
Morskoy pr. 2, 630090 Novosibirsk, Russia



Advanced Search

Journal of Applied Mechanics and Technical Physics

2021 year, number 6

1.
Determination of Threshold N-Factors of the Laminar-Turbulent Transition in a Subsonic Boundary Layer on a Prolate Spheroid

V. Boiko1, K. V. Demyank1,2, S. V. Kirilovskiy1, Yu. M. Nechepurenko1,2, T. V. Poplavskaya1
1Khristianovich Institute of Theoretical and Applied Mechanics, Siberian Branch, Russian Academy of Sciences, Novosibirsk, 630090, Russia
2Marchuk Institute of Numerical Mathematics, Russian Academy of Sciences, Moscow, 119333, Russia
Keywords: laminar-turbulent flow, methods of determining the transition position, e-method, threshold N-factors, numerical simulation

Abstract >>
Results of a numerical study of the laminar-turbulent transition in the boundary layer of a prolate spheroid obtained with the use of the ANSYS Fluent gas-dynamic software with an in-house developed module of the laminar-turbulent transition based on the e N-method are reported. Based on experimental data, a method of determining individual threshold N -factors for different transition mechanisms is proposed.



2.
Thermodynamic Consistency as a Method for Modeling Gas Flows at Channel Junctions

Yu. A. Dubravin
Moscow Aviation Institute, Moscow, 125993, Russia
dubravin_yu@mail.ru
Keywords: gas dynamics, channel junctions, the second law of thermodynamics, strong discontinuities, openness problem

Abstract >>
The gas-dynamic conservation laws in integral form for sections of channels which have a bend of the axis, a jump in the cross-section area or channel branching is an open system of equations. The openness problem is solved by a method based on the independence of the thermodynamic function (pressure recovery factor) on the specified geometric arguments. The mathematical model reduces to a closed system of nonlinear algebraic equations not requiring additional hypotheses and admitting a solution in explicit form for small Mach numbers.



3.
Discrete Method for Solving a Three-Point Boundary-Value Problem for a Third-Order Equation

A. F. Voevodin1, O. A. Frolovskaya1
Lavrent'ev Institute of Hydrodynamics, Siberian Branch, Russian Academy of Sciences, Novosibirsk, 630090, Russia
Keywords: boundary-value problem, coupled equation, difference scheme

Abstract >>
Coupled equations are used to develop a method for solving boundary-value problems for second- and third-order equations. With the use of the factorization method, a three-point boundary-value problem for a third-order equation is reduced to a system of first- and second-order equations. In order to solve the second-order equation, a discrete problem is constructed, which is then used to solve the main problem. This method is peculiar because discrete (difference) boundary-value problems are constructed without using approximations of differential operators. The method is generalized to solve higher-order equations.



4.
Dynamic Chaos and the (1/f) Spectrum in the Case of Interacting Nonequilibrium Phase Transitions

V. P. Koverda, V. N. Skokov
Institute of Thermal Physics, Ural Branch, Russian Academy of Sciences, Yekaterinburg, 620016, Russia
Keywords: dynamic chaos, (1/f) noise, nonequilibrium phase transitions, critical modes, maximum entropy

Abstract >>
A system of two nonlinear stochastic equations is used to simulate fluctuations near a critical transition. Their interaction results in extreme fluctuations of temperature and heat fluxes with a (1/f) spectrum in critical heat and mass transfer regimes. The interaction of large and small fluctuations in the critical domain is investigated, which can make it possible to explain the physical nature of (1/f) noise and large fluctuations with power-series amplitude distribution, as well as their interaction with classical fluctuations. In the case of external periodic action on a system with interacting nonequilibrium phase transitions, the chaotic regimes characterized by unstable pulsation cycles are determined.



5.
Numerical Analysis of Laminar Mixed Convection Heat Transfer of the Al2O3-H2O Nanofluid in a Square Channel

I. Rahmoune, S. Bougoul
University of Batna1, Batna, 05000, Algeria
Keywords: nanofluid,Al2O3 particles, mixed convection, laminar flow, channel, CFD

Abstract >>
In this study, the Al2O3-H2O nanofluid flow through a duct with a square cross section under a constant heat flux is simulated using a single-phase model. According to the chosen values of the Reynolds and modified Richardson numbers, this flow is laminar, and it is considered in mixed convection. The dynamic and thermal parameters of this flow are determined numerically by using the CFD-Fluent software based on the finite volume method by introducing the Boussinesq approximation. The analysis is carried out for Reynolds numbers ranging from 100 to 1000 and modified Richardson numbers equal to 0.1 and 0.5. The results obtained show that gravitational forces generate two thermo-convective cells in each cross section along the channel, and asymmetric temperature and velocity profiles are formed. The effects of the volume fraction of nanoparticles, Reynolds number, and modified Richardson number on the flow structure, Nusselt number, and pressure drop are analyzed. With the use of nanofluids, the Nusselt number increases, which ensures heat transfer enhancement. Finally, a correlation is proposed for the Nusselt number as a function of the nanoparticle volume fraction, which can be used for heat transfer predictions.



6.
Magnetic Field Generation in a Cylindrical Plasma using the Density Gradient

M. Niroozad, B. Farokhi
Arak University, Arak, Iran
Keywords: fast electron beam, cylindrical target, self-generated magnetic field, electron flow velocity

Abstract >>
In this research, we use the fluid theory in an efficient way to perform a theoretical study on a divergent flux of fast electrons produced during interaction of a high-power laser beam with a cylindrical over-dense target. Cylindrical targets consisting of a low-density core with high-density cladding structures are irradiated by an ultra-intense annular laser beam. The analytical model exhibits such structures with a density gradient generating a strong spontaneous interface magnetic field that can collimate the fast electron beam and prevent electrons from escaping. The magnetic field generated by such a cylindrical target is compared with that of planar targets. The results show that cylindrical structures have a more effective potential for producing spontaneous interface magnetic fields and reducing the transverse angular distribution of the fast electron beam. Thus, they will be adequate to increase the possibility of energy transmission to the main target for a more promising fast ignition scheme in inertial confinement fusion.



7.
Free Vibrations of a Vertical Support Comprised of Three Orthotropic Cylindrical Panels Reinforced with Cross Fibers in Contact with Viscously Elastic Soil

D. S. Ganiev
Azerbaijan University of Architecture and Construction, Baku, AZ1073, Azerbaijan
Keywords: bridge supports, natural vibrations, Hamilton's least-action principle

Abstract >>
Natural vibrations of supports comprised of three cylindrical panels supported by ring elements and soil are under study. A system of equations describing the problem is constructed using Hamilton's least-action principle. A dependence between the frequency characteristics and the geometric parameters of the support is investigated.



8.
Technologically Varied Reservoir Permeability during Nonisothermal Oil - Gas - Paraffin Filtering in the Case of Phase Transitions

L. A. Gaidukov1, A. V. Novikov2
1Oil and Gas Research Institute RAS, Moscow, 119333, Russia
2Gubkin Russian State University of Oil and Gas, Moscow, 119333, Russia
Keywords: filtration, permeability, wax, oil reservoir, pore space, mathematical model, phase transition

Abstract >>
Changes in temperature and pressure conditions during the development of an oil reservoir with a high paraffin content in a limiting saturated state causes an in-situ phase transition to a solid state, and the filtering of a mixture of oil with solid paraffin particles at a temperature below the flocculation temperature causes clogging in the pore space of the reservoir in narrow places and bottle necks of pores. Thus, laboratory studies are carried out to determine the critical points and parameters of an oil - gas - paraffin mixture under various thermobaric conditions. A mathematical model is developed that describes wax deposition in the pore space of a low-temperature oil reservoir and makes it possible to calculate its permeability during development. The model parameters are adapted to their experimental values. Numerical calculations are used to determine the values of the main parameters that affect the reservoir permeability.



9.
Method for Determining the Filtration Properties of a Fractured Porous Reservoir by Solving the Inverse Problem using Well Output Measurements

A. L. Karchevskii1, L. A. Nazarova2, L. A. Nazarov2
1Sobolev Institute of Mathematics, Siberian Branch, Russian Academy of Sciences, Novosibirsk, 630090, Russia
2Chinakal Institute of Mining, Siberian Branch, Russian Academy of Sciences, Novosibirsk, 630091, Russia
Keywords: dual-porosity model, permeability, pressure, flow rate, inverse problem, fractured porous reservoir

Abstract >>
A method for the quantitative evaluation of the matrix and fracture permeabilities was developed and algorithmically implemented within the framework of the dual-porosity continuum model describing mass transfer in a fractured porous reservoir. The method involves the solution of the inverse coefficient problem whose input data are the well flow rate characteristics measured in the stop-start operation mode. The algorithm is based on the obtained analytical solution of the direct problem of the evolution of hydrodynamic fields in the near-wellbore space. The results of numerical experiments show that the inverse problem has a unique solution with a moderate level of noise in the input data.



10.
Modeling the Effect of Preliminary Quasi-Static Loading on the Dynamic Buckling of Composite Cylindrical Shells under Axial Compressive Loading

N. A. Abrosimov, A. V. Elesin, L. A. Igumnov
Research Institute of Mechanics, Lobachevsky Nizhny Novgorod State University, Nizhny Novgorod, 603950, Russia
Keywords: composite materials, cylindrical shells, dynamic stability, numerical methods, quasi-static and dynamic loads

Abstract >>
Based on the applied theory of shells, an energetically consistent resolving system of equations has been formulated and a complex numerical method using an explicit variational-difference schemes has been developed to solve both quasi-static and dynamic problems of nonlinear nonaxisymmetric deformation and buckling of composite cylindrical shells. The reliability of the developed method is verified by comparing calculation results and experimental data. For various of reinforcement structures, an analysis of critical loads and characteristic forms of buckling of composite cylindrical shells previously subjected to quasi-static loading internal pressure followed by dynamic loading by axial compression.



11.
Investigation of Elastic Properties of a Material Obtained by Means of Cold Gas Dynamic Spraying with Laser Processing

A. V. Mishin1,2, V. M. Fomin1,2
1Khristianovich Institute of Theoretical and Applied Mechanics, Siberian Branch, Russian Academy of Sciences, Novosibirsk, 630090, Russia
2Novosibirsk State University, Novosibirsk, 630090, Russia
Keywords: heterogeneous medium, microstructure, stochastic models, averaging

Abstract >>
A heterogeneous material obtained by means of cold gas dynamic spraying with subsequent laser processing is studied. The reasons for reduction of the particle size of boron carbide B4C under the action of a laser beam and the chemical composition of the material containing the "lost" material of B4C particles are examined. A mathematical model, which takes into account the dissolution of B4C particles and the presence of a chemical reaction, is developed. The elastic properties of the deposited heterogeneous material are analyzed with the use of continuum approaches that describe heterogeneous media and are based on averaging of the original stochastic equations.



12.
Some Features of Fragmentation of an Aluminum Projectile at Various Velocities of Penetration into a Mesh Bumper

T. A. Shumikhin1, P. N. Kalmykov2, N. V. Lapichev2, A. I. Leont'ev2, D. E. Martyushov2, N. N. Myagkov1, V. N. Nomakonova2, A. V. Sal'nikov2, L. N. Bezrukov3
1Institute of Applied Mechanics, Russian Academy of Sciences, Moscow, 123040, Russia
2RFNC, All-Russian Research Institute of Experimental Physics, Sarov, 607188, Russia
3State Research Institute of Aviation Systems, Moscow, 125319, Russia
Keywords: high-velocity impact, fragmentation, mesh bumper, screen protection

Abstract >>
The fragmentation of projectiles penetrating into thin discrete bumpers is accompanied by ejections of material from the front part of the projectile in the direction of its movement. Material ejection from the front part of the projectile and fragments of the rear part of the projectile form two groups of fragments. The distribution of craters formed by these groups of fragments was analyzed, and the intensity and nature of the damage they caused and the effect of projectile velocity on the kinetic energy distribution between these groups were determined. Fragments were recorded using witness plates of great thicknesses placed at a certain distance behind the steel mesh bumper on the path of movement of fragments. It was found that with an increase in velocity, the proportion of specific kinetic energy of the front ejections increased and the fraction of the kinetic energy of the fragments of the rear of the projectile decreased. The kinetic energy distribution was determined in the case of fragmentation of a projectile of an aluminum alloy of 9 mm diameter on a tungsten mesh (wire diameter 0.5 mm, aperture 3.2 mm). The diameter of the projectile to the cell size of the tungsten mesh was the same as for steel mesh. Significant difference shown The kinetic energy distributions for the tungsten and steel mesh were found to be significantly different, probably due to the strength characteristics of the projectile material and the smaller wire diameter in experiments with the tungsten mesh. The features of damage to the witness plate by a group of small fragments were analyzed.



13.
Steady-State Creep of a Long Narrow Membrane Inside a High Rigid Matrix at Variable Lateral Pressure

A. M. Lokoshchenko, L. V. Fomin, Yu. G. Basalov
Institute of Mechanics, Moscow, 119192, Russia
Keywords: membrane, steady-state creep, high rigid matrix, variable lateral pressure, perfect glide, adhesion

Abstract >>
This paper describes a problem of steady-state creep of a long narrow rectangular membrane in the case of a linear dependence between the transverse pressure and time. The membrane is located inside a tall long rigid matrix with a rectangular cross section, the ratio of the height to half the width is greater than unity. A power-series relationship between the stress intensities and creep strain rates of the membrane is used. Two variants of contact conditions for the membrane and the matrix are considered: ideal sliding and adhesion. The analysis of the problem is carried out until the time at which the membrane is almost completely adjacent to the matrix walls. It is shown that, if the relative height of the membrane is smaller than a certain value, then the creep duration of the membrane until the moment at which it almost completely adjoins the matrix walls is shorter in the case of ideal sliding than in the case of adhesion, and vice versa. An explanation of this effect is provided.



14.
Optimization of Oxide-Based Activating Flux Combination Formula in Activated Tungsten Inert Gas Welding using a Hybrid Method Including Artificial Neural Networks and Particle Swarm Optimization

M. Azadi Moghaddam, F. Kolahan
Ferdowsi University of Mashhad, Mashhad, Iran
Keywords: activated tungsten inert gas (A-TIG) welding process, response surface methodology (RSM), artificial neural network (ANN), particle swarm optimization (PSO) algorithm, and simulated annealing (SA) algorithm

Abstract >>
The effects of the most important process-adjusting variables (welding current and welding speed) and the percentage of the combination of TiO2 and SiO2 activating fluxes on the most important quality characteristics (weld bead width, depth of penetration, and aspect ratio of these parameters) in welding of AISI316L austenite stainless steel parts are considered. Artificial neural networks (ANN) are used to determine the relations between the input variables and output responses of the activated tungsten inert gas (A-TIG) welding process. To determine the proper ANN architecture (the proper number of hidden layers and their corresponding neurons/nodes), the particle swarm optimization (PSO) method is used. Experimental tests are conducted to evaluate the proposed procedure performance. Based on the results, the proposed method is found to be efficient in modeling and optimization of the A-TIG welding process.



15.
Nonstationary Thermokinetic Model of Surface Laser Scanning

A. G. Knyazeva
Institute of Strength Physics and Materials Science, Siberian Branch, Russian Academy of Sciences, Tomsk, 634055, Russia
Keywords: surface laser scanning, numerical simulation, temperature field, porosity evolution, shrinkage, surface topography, thermal cycles

Abstract >>
This paper presents a thermophysical model of laser beam scanning of the surface of a two-layer plate, whose top layer melts and shrinks due to changes in porosity, and whose bottom layer (substrate) does not melt. The dependences of the heat capacity, thermal conductivity, and reflection coefficient on porosity are taken into account. Heat loss is due to both radiation and convection. Results are presented showing that the process is nonstationary throughout the scan. It is shown that the complex thermal cycles and inhomogeneous temperature field are directly related to inhomogeneous shrinkage, leading to the surface topography typical of selective laser melting processes.



16.
Detachment of Inhomogeneous Coating

A. O. Vatul'yan, K. L. Morozov
, Rostov-on-Don, 344049, Russia
Keywords: detachment, thin coating, bedding values, supercritical behavior, Ritz method

Abstract >>
This paper describes a study of buckling and supercritical behavior of inhomogeneous coatings. On the basis of the variational interpretation of the problem and the Ritz method, the change in the first critical value of the load at which buckling occurs, depending on the problem parameters. Calculations are carried out for inhomogeneous coating of two types: coatings with piecewise constant stiffness and coatings with a continuously changing maximum inside and outside the detachment zone. The supercritical behavior of the coating is studied.



17.
Influence of Heat Treatment of Laser-Welded Joints of Aluminum-Lithium Alloys on the Instability of Plastic Flow

E. V. Karpov1, A. G. Malikov2, A. M. Orishich2
1Lavrent'ev Institute of Hydrodynamics, Siberian Branch, Russian Academy of Sciences, Novosibirsk, 630090, Russia
2Khristianovich Institute of Theoretical and Applied Mechanics, Siberian Branch, Russian Academy of Sciences, Novosibirsk, 630090, Russia
Keywords: aluminum-lithium alloy, discontinuous yield, heat treatment, phase composition, Portevin-Le Chatelier effect

Abstract >>
This paper presents an analysis of the experimentally observed evolution of the unstable plastic flow obtained by laser welding of samples of aluminum-lithium alloys of the Al-6Mg-2Li, Al-1,6Cu-1,1Mg-1,8Li, Al-3,4Cu-0,66Mg-1,5Li systems, under various heat treatment conditions after welding. Comparison of the discontinuous yield of alloys with different concentrations of magnesium, copper, and lithium was performed. The effect of copper on the spatial consistency of the localized shear bands formed in aluminum-lithium alloys under unstable plastic flow.



18.
Development of an Optimal Composition of Three-Species High-Strength Wear-Resistant Composites Based on Polyimide

S. V. Panin1,2, J. Luo2, D. G. Buslovich1, L. A. Kornienko1, V. O. Aleksenko1, S. A. Bochkareva1
1Institute of Strength Physics and Materials Science, Siberian Branch, Russian Academy of Sciences, Tomsk, 634055, Russia
2Tomsk Polytechnical University, Tomsk, 634050, Russia
Keywords: polyimide, carbon fibers, polytetrafluoroethylene, strength, wear-resistance, optimal design

Abstract >>
Mechanical and tribological properties of polyimide-based three-species antifriction composites filled with polytetrafluoroethylene and milled carbon fibers with a mass fraction of 5-15% are studied. It is shown that the elasticity modulus can be almost doubled by adding milled carbon fibers. The study of tribological characteristics shows that the wear of surfaces can be reduced by using the above-mentioned complex filler by a factor of 265 in the case of metal-polymer tribocoupling and by a factor of 255 in the case of ceramic-polymer tribocoupling. Optimal compositions of the polyimide-based three-species solid lubricant composite to be used in the cases of metal-polymer and ceramic-polymer tribocoupling are determined by using an in-house computer algorithm.



19.
Structural Modification of Explosive Chambers and Numerical Calculations of Their Stress-Strain State

Yu. P. Meshcheryakov1, B. S. Zlobin1, A. A. Shtertser1,2
1Design and Engineering Branch of the Lavrent'ev Institute of Hydrodynamics, Siberian Branch of the Russian Academy of Sciences, Novosibirsk, 630090, Russia
2Lavrent'ev Institute of Hydrodynamics, Siberian Branch of the Russian Academy of Sciences, Novosibirsk, 630090, Russia
Keywords: explosion chamber, synchrotron radiation, numerical simulation, equivalent stresses

Abstract >>
Explosion chamber modification is proposed. It is intended for studying detonation and shock-wave processes using synchrotron radiation. Examples of explosive chamber designs that meet the necessary conditions are given. Numerical simulation is used to obtain a dependence between the degree of inhomogeneity of the stress state of an explosion chamber shell and the ratio of the shell radius to its thickness.